Fixed various memory leaks and Java 8 JNI Compatibility

Summary:
I have manually audited the entire RocksJava code base.

Sorry for the large pull-request, I have broken it down into many small atomic commits though.

My initial intention was to fix the warnings that appear when running RocksJava on Java 8 with `-Xcheck:jni`, for example when running `make jtest` you would see many errors similar to:

```
WARNING in native method: JNI call made without checking exceptions when required to from CallObjectMethod
WARNING in native method: JNI call made without checking exceptions when required to from CallVoidMethod
WARNING in native method: JNI call made without checking exceptions when required to from CallStaticVoidMethod
...
```

A few of those warnings still remain, however they seem to come directly from the JVM and are not directly related to RocksJava; I am in contact with the OpenJDK hostpot-dev mailing list about these - http://mail.openjdk.java.net/pipermail/hotspot-dev/2017-February/025981.html.

As a result of fixing these, I realised we were not r
Closes https://github.com/facebook/rocksdb/pull/1890

Differential Revision: D4591758

Pulled By: siying

fbshipit-source-id: 7f7fdf4

java/Makefile

@@ -18,7 +18,6 @@ NATIVE_JAVA_CLASSES = org.rocksdb.AbstractCompactionFilter\
 	org.rocksdb.ExternalSstFileInfo\
 	org.rocksdb.FlushOptions\
 	org.rocksdb.Filter\
-	org.rocksdb.GenericRateLimiterConfig\
 	org.rocksdb.HashLinkedListMemTableConfig\
 	org.rocksdb.HashSkipListMemTableConfig\
 	org.rocksdb.Logger\
@@ -91,6 +90,7 @@ JAVA_TESTS = org.rocksdb.BackupableDBOptionsTest\
         org.rocksdb.NativeLibraryLoaderTest\
 	org.rocksdb.OptionsTest\
 	org.rocksdb.PlainTableConfigTest\
+	org.rocksdb.RateLimiterTest\
 	org.rocksdb.ReadOnlyTest\
 	org.rocksdb.ReadOptionsTest\
 	org.rocksdb.RocksDBTest\
@@ -136,6 +136,14 @@ JAVA_TESTCLASSPATH = $(JAVA_JUNIT_JAR):$(JAVA_HAMCR_JAR):$(JAVA_MOCKITO_JAR):$(J
 
 MVN_LOCAL = ~/.m2/repository
 
+# Set the default JAVA_ARGS to "" for DEBUG_LEVEL=0
+JAVA_ARGS? =
+
+# When debugging add -Xcheck:jni to the java args
+ifneq ($(DEBUG_LEVEL),0)
+	JAVA_ARGS = -ea -Xcheck:jni
+endif
+
 clean:
 	$(AM_V_at)rm -rf include/*
 	$(AM_V_at)rm -rf test-libs/
@@ -164,7 +172,7 @@ sample: java
 	$(AM_V_at)javac -cp $(MAIN_CLASSES) -d $(SAMPLES_MAIN_CLASSES) $(SAMPLES_MAIN_SRC)/RocksDBSample.java
 	$(AM_V_at)@rm -rf /tmp/rocksdbjni
 	$(AM_V_at)@rm -rf /tmp/rocksdbjni_not_found
-	java -ea -Xcheck:jni -Djava.library.path=target -cp $(MAIN_CLASSES):$(SAMPLES_MAIN_CLASSES) RocksDBSample /tmp/rocksdbjni
+	java $(JAVA_ARGS) -Djava.library.path=target -cp $(MAIN_CLASSES):$(SAMPLES_MAIN_CLASSES) RocksDBSample /tmp/rocksdbjni
 	$(AM_V_at)@rm -rf /tmp/rocksdbjni
 	$(AM_V_at)@rm -rf /tmp/rocksdbjni_not_found
 
@@ -172,7 +180,7 @@ column_family_sample: java
 	$(AM_V_GEN)mkdir -p $(SAMPLES_MAIN_CLASSES)
 	$(AM_V_at)javac -cp $(MAIN_CLASSES) -d $(SAMPLES_MAIN_CLASSES) $(SAMPLES_MAIN_SRC)/RocksDBColumnFamilySample.java
 	$(AM_V_at)@rm -rf /tmp/rocksdbjni
-	java -ea -Xcheck:jni -Djava.library.path=target -cp $(MAIN_CLASSES):$(SAMPLES_MAIN_CLASSES) RocksDBColumnFamilySample /tmp/rocksdbjni
+	java $(JAVA_ARGS) -Djava.library.path=target -cp $(MAIN_CLASSES):$(SAMPLES_MAIN_CLASSES) RocksDBColumnFamilySample /tmp/rocksdbjni
 	$(AM_V_at)@rm -rf /tmp/rocksdbjni
 
 resolve_test_deps:
@@ -194,7 +202,7 @@ java_test: java resolve_test_deps
 test: java java_test run_test
 
 run_test:
-	java -ea -Djava.library.path=target -cp "$(MAIN_CLASSES):$(TEST_CLASSES):$(JAVA_TESTCLASSPATH):target/*" org.rocksdb.test.RocksJunitRunner $(JAVA_TESTS)
+	java $(JAVA_ARGS) -Djava.library.path=target -cp "$(MAIN_CLASSES):$(TEST_CLASSES):$(JAVA_TESTCLASSPATH):target/*" org.rocksdb.test.RocksJunitRunner $(JAVA_TESTS)
 
 db_bench: java
 	$(AM_V_GEN)mkdir -p $(BENCHMARK_MAIN_CLASSES)

java/benchmark/src/main/java/org/rocksdb/benchmark/DbBenchmark.java

@@ -572,7 +572,7 @@ public class DbBenchmark {
         (Integer)flags_.get(Flag.num_levels));
     options.setTargetFileSizeBase(
         (Integer)flags_.get(Flag.target_file_size_base));
-    options.setTargetFileSizeMultiplier((Double) flags_.get(Flag.target_file_size_multiplier));
+    options.setTargetFileSizeMultiplier((Integer)flags_.get(Flag.target_file_size_multiplier));
     options.setMaxBytesForLevelBase(
         (Integer)flags_.get(Flag.max_bytes_for_level_base));
     options.setMaxBytesForLevelMultiplier((Double) flags_.get(Flag.max_bytes_for_level_multiplier));
@@ -588,12 +588,10 @@ public class DbBenchmark {
         (Double)flags_.get(Flag.hard_rate_limit));
     options.setRateLimitDelayMaxMilliseconds(
         (Integer)flags_.get(Flag.rate_limit_delay_max_milliseconds));
-    options.setMaxGrandparentOverlapFactor(
+    options.setMaxCompactionBytes(
-        (Integer)flags_.get(Flag.max_grandparent_overlap_factor));
+        (Long) flags_.get(Flag.max_compaction_bytes));
     options.setDisableAutoCompactions(
         (Boolean)flags_.get(Flag.disable_auto_compactions));
-    options.setSourceCompactionFactor(
-        (Integer)flags_.get(Flag.source_compaction_factor));
     options.setMaxSuccessiveMerges(
         (Integer)flags_.get(Flag.max_successive_merges));
     options.setWalTtlSeconds((Long)flags_.get(Flag.wal_ttl_seconds));
@@ -978,7 +976,7 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    write_buffer_size(4 * SizeUnit.MB,
+    write_buffer_size(4L * SizeUnit.MB,
         "Number of bytes to buffer in memtable before compacting\n" +
         "\t(initialized to default value by 'main'.)") {
       @Override public Object parseValue(String value) {
@@ -1056,7 +1054,7 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    numdistinct(1000,
+    numdistinct(1000L,
         "Number of distinct keys to use. Used in RandomWithVerify to\n" +
         "\tread/write on fewer keys so that gets are more likely to find the\n" +
         "\tkey and puts are more likely to update the same key.") {
@@ -1064,7 +1062,7 @@ public class DbBenchmark {
         return Long.parseLong(value);
       }
     },
-    merge_keys(-1,
+    merge_keys(-1L,
         "Number of distinct keys to use for MergeRandom and\n" +
         "\tReadRandomMergeRandom.\n" +
         "\tIf negative, there will be FLAGS_num keys.") {
@@ -1169,7 +1167,7 @@ public class DbBenchmark {
         return Long.parseLong(value);
       }
     },
-    compressed_cache_size(-1,
+    compressed_cache_size(-1L,
         "Number of bytes to use as a cache of compressed data.") {
       @Override public Object parseValue(String value) {
         return Long.parseLong(value);
@@ -1188,7 +1186,7 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    memtable_bloom_size_ratio(0, "Ratio of memtable used by the bloom filter.\n"
+    memtable_bloom_size_ratio(0.0d, "Ratio of memtable used by the bloom filter.\n"
             + "\t0 means no bloom filter.") {
       @Override public Object parseValue(String value) {
         return Double.parseDouble(value);
@@ -1212,7 +1210,7 @@ public class DbBenchmark {
         return parseBoolean(value);
       }
     },
-    writes(-1,"Number of write operations to do. If negative, do\n" +
+    writes(-1L, "Number of write operations to do. If negative, do\n" +
         "\t--num reads.") {
       @Override public Object parseValue(String value) {
         return Long.parseLong(value);
@@ -1255,7 +1253,7 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    max_bytes_for_level_multiplier(10,
+    max_bytes_for_level_multiplier(10.0d,
         "A multiplier to compute max bytes for level-N (N >= 2)") {
       @Override public Object parseValue(String value) {
         return Double.parseDouble(value);
@@ -1337,7 +1335,7 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    stats_interval(0,"Stats are reported every N operations when\n" +
+    stats_interval(0L, "Stats are reported every N operations when\n" +
         "\tthis is greater than zero. When 0 the interval grows over time.") {
       @Override public Object parseValue(String value) {
         return Long.parseLong(value);
@@ -1354,12 +1352,12 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    soft_rate_limit(0.0,"") {
+    soft_rate_limit(0.0d,"") {
       @Override public Object parseValue(String value) {
         return Double.parseDouble(value);
       }
     },
-    hard_rate_limit(0.0,"When not equal to 0 this make threads\n" +
+    hard_rate_limit(0.0d,"When not equal to 0 this make threads\n" +
         "\tsleep at each stats reporting interval until the compaction\n" +
         "\tscore for all levels is less than or equal to this value.") {
       @Override public Object parseValue(String value) {
@@ -1373,11 +1371,10 @@ public class DbBenchmark {
         return Integer.parseInt(value);
       }
     },
-    max_grandparent_overlap_factor(10,"Control maximum bytes of\n" +
+    max_compaction_bytes(0L, "Limit number of bytes in one compaction to be lower than this\n" +
-        "\toverlaps in grandparent (i.e., level+2) before we stop building a\n" +
+            "\threshold. But it's not guaranteed.") {
-        "\tsingle file in a level->level+1 compaction.") {
       @Override public Object parseValue(String value) {
-        return Integer.parseInt(value);
+        return Long.parseLong(value);
       }
     },
     readonly(false,"Run read only benchmarks.") {
@@ -1390,13 +1387,6 @@ public class DbBenchmark {
         return parseBoolean(value);
       }
     },
-    source_compaction_factor(1,"Cap the size of data in level-K for\n" +
-        "\ta compaction run that compacts Level-K with Level-(K+1) (for\n" +
-        "\tK >= 1)") {
-      @Override public Object parseValue(String value) {
-        return Integer.parseInt(value);
-      }
-    },
     wal_ttl_seconds(0L,"Set the TTL for the WAL Files in seconds.") {
       @Override public Object parseValue(String value) {
         return Long.parseLong(value);

java/rocksjni/backupablejni.cc

@@ -27,8 +27,12 @@
  */
 jlong Java_org_rocksdb_BackupableDBOptions_newBackupableDBOptions(
     JNIEnv* env, jclass jcls, jstring jpath) {
-  const char* cpath = env->GetStringUTFChars(jpath, NULL);
+  const char* cpath = env->GetStringUTFChars(jpath, nullptr);
-  auto bopt = new rocksdb::BackupableDBOptions(cpath);
+  if(cpath == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return 0;
+  }
+  auto* bopt = new rocksdb::BackupableDBOptions(cpath);
   env->ReleaseStringUTFChars(jpath, cpath);
   return reinterpret_cast<jlong>(bopt);
 }
@@ -40,7 +44,7 @@ jlong Java_org_rocksdb_BackupableDBOptions_newBackupableDBOptions(
  */
 jstring Java_org_rocksdb_BackupableDBOptions_backupDir(
     JNIEnv* env, jobject jopt, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return env->NewStringUTF(bopt->backup_dir.c_str());
 }
 
@@ -51,7 +55,7 @@ jstring Java_org_rocksdb_BackupableDBOptions_backupDir(
  */
 void Java_org_rocksdb_BackupableDBOptions_setShareTableFiles(
     JNIEnv* env, jobject jobj, jlong jhandle, jboolean flag) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->share_table_files = flag;
 }
 
@@ -62,7 +66,7 @@ void Java_org_rocksdb_BackupableDBOptions_setShareTableFiles(
  */
 jboolean Java_org_rocksdb_BackupableDBOptions_shareTableFiles(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->share_table_files;
 }
 
@@ -73,7 +77,7 @@ jboolean Java_org_rocksdb_BackupableDBOptions_shareTableFiles(
  */
 void Java_org_rocksdb_BackupableDBOptions_setSync(
     JNIEnv* env, jobject jobj, jlong jhandle, jboolean flag) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->sync = flag;
 }
 
@@ -84,7 +88,7 @@ void Java_org_rocksdb_BackupableDBOptions_setSync(
  */
 jboolean Java_org_rocksdb_BackupableDBOptions_sync(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->sync;
 }
 
@@ -95,7 +99,7 @@ jboolean Java_org_rocksdb_BackupableDBOptions_sync(
  */
 void Java_org_rocksdb_BackupableDBOptions_setDestroyOldData(
     JNIEnv* env, jobject jobj, jlong jhandle, jboolean flag) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->destroy_old_data = flag;
 }
 
@@ -106,7 +110,7 @@ void Java_org_rocksdb_BackupableDBOptions_setDestroyOldData(
  */
 jboolean Java_org_rocksdb_BackupableDBOptions_destroyOldData(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->destroy_old_data;
 }
 
@@ -117,7 +121,7 @@ jboolean Java_org_rocksdb_BackupableDBOptions_destroyOldData(
  */
 void Java_org_rocksdb_BackupableDBOptions_setBackupLogFiles(
     JNIEnv* env, jobject jobj, jlong jhandle, jboolean flag) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->backup_log_files = flag;
 }
 
@@ -128,7 +132,7 @@ void Java_org_rocksdb_BackupableDBOptions_setBackupLogFiles(
  */
 jboolean Java_org_rocksdb_BackupableDBOptions_backupLogFiles(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->backup_log_files;
 }
 
@@ -139,7 +143,7 @@ jboolean Java_org_rocksdb_BackupableDBOptions_backupLogFiles(
  */
 void Java_org_rocksdb_BackupableDBOptions_setBackupRateLimit(
     JNIEnv* env, jobject jobj, jlong jhandle, jlong jbackup_rate_limit) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->backup_rate_limit = jbackup_rate_limit;
 }
 
@@ -150,7 +154,7 @@ void Java_org_rocksdb_BackupableDBOptions_setBackupRateLimit(
  */
 jlong Java_org_rocksdb_BackupableDBOptions_backupRateLimit(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->backup_rate_limit;
 }
 
@@ -161,7 +165,7 @@ jlong Java_org_rocksdb_BackupableDBOptions_backupRateLimit(
  */
 void Java_org_rocksdb_BackupableDBOptions_setRestoreRateLimit(
     JNIEnv* env, jobject jobj, jlong jhandle, jlong jrestore_rate_limit) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->restore_rate_limit = jrestore_rate_limit;
 }
 
@@ -172,7 +176,7 @@ void Java_org_rocksdb_BackupableDBOptions_setRestoreRateLimit(
  */
 jlong Java_org_rocksdb_BackupableDBOptions_restoreRateLimit(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->restore_rate_limit;
 }
 
@@ -183,7 +187,7 @@ jlong Java_org_rocksdb_BackupableDBOptions_restoreRateLimit(
  */
 void Java_org_rocksdb_BackupableDBOptions_setShareFilesWithChecksum(
     JNIEnv* env, jobject jobj, jlong jhandle, jboolean flag) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   bopt->share_files_with_checksum = flag;
 }
 
@@ -194,7 +198,7 @@ void Java_org_rocksdb_BackupableDBOptions_setShareFilesWithChecksum(
  */
 jboolean Java_org_rocksdb_BackupableDBOptions_shareFilesWithChecksum(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   return bopt->share_files_with_checksum;
 }
 
@@ -205,7 +209,7 @@ jboolean Java_org_rocksdb_BackupableDBOptions_shareFilesWithChecksum(
  */
 void Java_org_rocksdb_BackupableDBOptions_disposeInternal(
     JNIEnv* env, jobject jopt, jlong jhandle) {
-  auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
+  auto* bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
-  assert(bopt);
+  assert(bopt != nullptr);
   delete bopt;
 }

java/rocksjni/backupenginejni.cc

@@ -82,11 +82,15 @@ jintArray Java_org_rocksdb_BackupEngine_getCorruptedBackups(
   backup_engine->GetCorruptedBackups(&backup_ids);
   // store backupids in int array
   std::vector<jint> int_backup_ids(backup_ids.begin(), backup_ids.end());
+  
   // Store ints in java array
-  jintArray ret_backup_ids;
   // Its ok to loose precision here (64->32)
   jsize ret_backup_ids_size = static_cast<jsize>(backup_ids.size());
-  ret_backup_ids = env->NewIntArray(ret_backup_ids_size);
+  jintArray ret_backup_ids = env->NewIntArray(ret_backup_ids_size);
+  if(ret_backup_ids == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return nullptr;
+  }
   env->SetIntArrayRegion(ret_backup_ids, 0, ret_backup_ids_size,
       int_backup_ids.data());
   return ret_backup_ids;
@@ -155,14 +159,24 @@ void Java_org_rocksdb_BackupEngine_restoreDbFromBackup(
     JNIEnv* env, jobject jbe, jlong jbe_handle, jint jbackup_id,
     jstring jdb_dir, jstring jwal_dir, jlong jrestore_options_handle) {
   auto* backup_engine = reinterpret_cast<rocksdb::BackupEngine*>(jbe_handle);
-  const char* db_dir = env->GetStringUTFChars(jdb_dir, 0);
+  const char* db_dir = env->GetStringUTFChars(jdb_dir, nullptr);
-  const char* wal_dir = env->GetStringUTFChars(jwal_dir, 0);
+  if(db_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+  const char* wal_dir = env->GetStringUTFChars(jwal_dir, nullptr);
+  if(wal_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    env->ReleaseStringUTFChars(jdb_dir, db_dir);
+    return;
+  }
   auto* restore_options =
       reinterpret_cast<rocksdb::RestoreOptions*>(jrestore_options_handle);
   auto status =
       backup_engine->RestoreDBFromBackup(
           static_cast<rocksdb::BackupID>(jbackup_id), db_dir, wal_dir,
           *restore_options);
+
   env->ReleaseStringUTFChars(jwal_dir, wal_dir);
   env->ReleaseStringUTFChars(jdb_dir, db_dir);
 
@@ -182,13 +196,23 @@ void Java_org_rocksdb_BackupEngine_restoreDbFromLatestBackup(
     JNIEnv* env, jobject jbe, jlong jbe_handle, jstring jdb_dir,
     jstring jwal_dir, jlong jrestore_options_handle) {
   auto* backup_engine = reinterpret_cast<rocksdb::BackupEngine*>(jbe_handle);
-  const char* db_dir = env->GetStringUTFChars(jdb_dir, 0);
+  const char* db_dir = env->GetStringUTFChars(jdb_dir, nullptr);
-  const char* wal_dir = env->GetStringUTFChars(jwal_dir, 0);
+  if(db_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+  const char* wal_dir = env->GetStringUTFChars(jwal_dir, nullptr);
+  if(wal_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    env->ReleaseStringUTFChars(jdb_dir, db_dir);
+    return;
+  }
   auto* restore_options =
       reinterpret_cast<rocksdb::RestoreOptions*>(jrestore_options_handle);
   auto status =
       backup_engine->RestoreDBFromLatestBackup(db_dir, wal_dir,
           *restore_options);
+
   env->ReleaseStringUTFChars(jwal_dir, wal_dir);
   env->ReleaseStringUTFChars(jdb_dir, db_dir);
 
@@ -206,5 +230,7 @@ void Java_org_rocksdb_BackupEngine_restoreDbFromLatestBackup(
  */
 void Java_org_rocksdb_BackupEngine_disposeInternal(
     JNIEnv* env, jobject jbe, jlong jbe_handle) {
-  delete reinterpret_cast<rocksdb::BackupEngine*>(jbe_handle);
+  auto* be = reinterpret_cast<rocksdb::BackupEngine*>(jbe_handle);
+  assert(be != nullptr);
+  delete be;
 }

java/rocksjni/checkpoint.cc

@@ -22,7 +22,7 @@
  */
 jlong Java_org_rocksdb_Checkpoint_newCheckpoint(JNIEnv* env,
     jclass jclazz, jlong jdb_handle) {
-  auto db = reinterpret_cast<rocksdb::DB*>(jdb_handle);
+  auto* db = reinterpret_cast<rocksdb::DB*>(jdb_handle);
   rocksdb::Checkpoint* checkpoint;
   rocksdb::Checkpoint::Create(db, &checkpoint);
   return reinterpret_cast<jlong>(checkpoint);
@@ -35,8 +35,8 @@ jlong Java_org_rocksdb_Checkpoint_newCheckpoint(JNIEnv* env,
  */
 void Java_org_rocksdb_Checkpoint_disposeInternal(JNIEnv* env, jobject jobj,
     jlong jhandle) {
-  auto checkpoint = reinterpret_cast<rocksdb::Checkpoint*>(jhandle);
+  auto* checkpoint = reinterpret_cast<rocksdb::Checkpoint*>(jhandle);
-  assert(checkpoint);
+  assert(checkpoint != nullptr);
   delete checkpoint;
 }
 
@@ -48,13 +48,20 @@ void Java_org_rocksdb_Checkpoint_disposeInternal(JNIEnv* env, jobject jobj,
 void Java_org_rocksdb_Checkpoint_createCheckpoint(
     JNIEnv* env, jobject jobj, jlong jcheckpoint_handle,
     jstring jcheckpoint_path) {
-  auto checkpoint = reinterpret_cast<rocksdb::Checkpoint*>(
-      jcheckpoint_handle);
   const char* checkpoint_path = env->GetStringUTFChars(
       jcheckpoint_path, 0);
+  if(checkpoint_path == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
+  auto* checkpoint = reinterpret_cast<rocksdb::Checkpoint*>(
+      jcheckpoint_handle);
   rocksdb::Status s = checkpoint->CreateCheckpoint(
       checkpoint_path);
+  
   env->ReleaseStringUTFChars(jcheckpoint_path, checkpoint_path);
+  
   if (!s.ok()) {
       rocksdb::RocksDBExceptionJni::ThrowNew(env, s);
   }

java/rocksjni/columnfamilyhandle.cc

@@ -20,6 +20,7 @@
  */
 void Java_org_rocksdb_ColumnFamilyHandle_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  auto it = reinterpret_cast<rocksdb::ColumnFamilyHandle*>(handle);
+  auto* cfh = reinterpret_cast<rocksdb::ColumnFamilyHandle*>(handle);
-  delete it;
+  assert(cfh != nullptr);
+  delete cfh;
 }

java/rocksjni/compaction_filter.cc

@@ -20,6 +20,8 @@
  */
 void Java_org_rocksdb_AbstractCompactionFilter_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::CompactionFilter*>(handle);
+  auto* cf = reinterpret_cast<rocksdb::CompactionFilter*>(handle);
+  assert(cf != nullptr);
+  delete cf;
 }
 // </editor-fold>

java/rocksjni/comparator.cc

@@ -27,7 +27,9 @@
  */
 void Java_org_rocksdb_AbstractComparator_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::BaseComparatorJniCallback*>(handle);
+  auto* bcjc = reinterpret_cast<rocksdb::BaseComparatorJniCallback*>(handle);
+  assert(bcjc != nullptr);
+  delete bcjc;
 }
 // </editor-fold>
 

java/rocksjni/comparatorjnicallback.cc

@@ -17,35 +17,60 @@ BaseComparatorJniCallback::BaseComparatorJniCallback(
     mtx_findShortestSeparator(new port::Mutex(copt->use_adaptive_mutex)) {
   // Note: Comparator methods may be accessed by multiple threads,
   // so we ref the jvm not the env
-  const jint rs __attribute__((unused)) = env->GetJavaVM(&m_jvm);
+  const jint rs = env->GetJavaVM(&m_jvm);
-  assert(rs == JNI_OK);
+  if(rs != JNI_OK) {
+    // exception thrown
+    return;
+  }
 
   // Note: we want to access the Java Comparator instance
   // across multiple method calls, so we create a global ref
+  assert(jComparator != nullptr);
   m_jComparator = env->NewGlobalRef(jComparator);
+  if(m_jComparator == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   // Note: The name of a Comparator will not change during it's lifetime,
   // so we cache it in a global var
   jmethodID jNameMethodId = AbstractComparatorJni::getNameMethodId(env);
+  if(jNameMethodId == nullptr) {
+    // exception thrown: NoSuchMethodException or OutOfMemoryError
+    return;
+  }
   jstring jsName = (jstring)env->CallObjectMethod(m_jComparator, jNameMethodId);
-  m_name = JniUtil::copyString(env, jsName);  // also releases jsName
+  if(env->ExceptionCheck()) {
+    // exception thrown
+    return;
+  }
+  jboolean has_exception = JNI_FALSE;
+  m_name = JniUtil::copyString(env, jsName,
+      &has_exception);  // also releases jsName
+  if (has_exception == JNI_TRUE) {
+    // exception thrown
+    return;
+  }
 
   m_jCompareMethodId = AbstractComparatorJni::getCompareMethodId(env);
+  if(m_jCompareMethodId == nullptr) {
+    // exception thrown: NoSuchMethodException or OutOfMemoryError
+    return;
+  }
+
   m_jFindShortestSeparatorMethodId =
     AbstractComparatorJni::getFindShortestSeparatorMethodId(env);
+  if(m_jFindShortestSeparatorMethodId == nullptr) {
+    // exception thrown: NoSuchMethodException or OutOfMemoryError
+    return;
+  }
+
   m_jFindShortSuccessorMethodId =
     AbstractComparatorJni::getFindShortSuccessorMethodId(env);
-}
+  if(m_jFindShortSuccessorMethodId == nullptr) {
-
+    // exception thrown: NoSuchMethodException or OutOfMemoryError
-/**
+    return;
- * Attach/Get a JNIEnv for the current native thread
+  }
- */
-JNIEnv* BaseComparatorJniCallback::getJniEnv() const {
-  JNIEnv *env;
-  jint rs __attribute__((unused)) =
-      m_jvm->AttachCurrentThread(reinterpret_cast<void**>(&env), NULL);
-  assert(rs == JNI_OK);
-  return env;
 }
 
 const char* BaseComparatorJniCallback::Name() const {
@@ -53,22 +78,50 @@ const char* BaseComparatorJniCallback::Name() const {
 }
 
 int BaseComparatorJniCallback::Compare(const Slice& a, const Slice& b) const {
-  JNIEnv* m_env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
+  assert(env != nullptr);
 
   // TODO(adamretter): slice objects can potentially be cached using thread
   // local variables to avoid locking. Could make this configurable depending on
   // performance.
   mtx_compare->Lock();
 
-  AbstractSliceJni::setHandle(m_env, m_jSliceA, &a, JNI_FALSE);
+  bool pending_exception =
-  AbstractSliceJni::setHandle(m_env, m_jSliceB, &b, JNI_FALSE);
+      AbstractSliceJni::setHandle(env, m_jSliceA, &a, JNI_FALSE);
+  if(pending_exception) {
+    if(env->ExceptionCheck()) {
+      // exception thrown from setHandle or descendant
+      env->ExceptionDescribe(); // print out exception to stderr
+    }
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return 0;
+  }
+
+  pending_exception =
+      AbstractSliceJni::setHandle(env, m_jSliceB, &b, JNI_FALSE);
+  if(pending_exception) {
+    if(env->ExceptionCheck()) {
+      // exception thrown from setHandle or descendant
+      env->ExceptionDescribe(); // print out exception to stderr
+    }
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return 0;
+  }
+  
   jint result =
-    m_env->CallIntMethod(m_jComparator, m_jCompareMethodId, m_jSliceA,
+    env->CallIntMethod(m_jComparator, m_jCompareMethodId, m_jSliceA,
       m_jSliceB);
 
   mtx_compare->Unlock();
 
-  m_jvm->DetachCurrentThread();
+  if(env->ExceptionCheck()) {
+    // exception thrown from CallIntMethod
+    env->ExceptionDescribe(); // print out exception to stderr
+    result = 0; // we could not get a result from java callback so use 0
+  }
+
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
 
   return result;
 }
@@ -79,32 +132,80 @@ void BaseComparatorJniCallback::FindShortestSeparator(
     return;
   }
 
-  JNIEnv* m_env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
+  assert(env != nullptr);
 
   const char* startUtf = start->c_str();
-  jstring jsStart = m_env->NewStringUTF(startUtf);
+  jstring jsStart = env->NewStringUTF(startUtf);
+  if(jsStart == nullptr) {
+    // unable to construct string
+    if(env->ExceptionCheck()) {
+      env->ExceptionDescribe(); // print out exception to stderr
+    }
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  }
+  if(env->ExceptionCheck()) {
+    // exception thrown: OutOfMemoryError
+    env->ExceptionDescribe(); // print out exception to stderr
+    env->DeleteLocalRef(jsStart);
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  }
 
   // TODO(adamretter): slice object can potentially be cached using thread local
   // variable to avoid locking. Could make this configurable depending on
   // performance.
   mtx_findShortestSeparator->Lock();
 
-  AbstractSliceJni::setHandle(m_env, m_jSliceLimit, &limit, JNI_FALSE);
+  bool pending_exception =
+      AbstractSliceJni::setHandle(env, m_jSliceLimit, &limit, JNI_FALSE);
+  if(pending_exception) {
+    if(env->ExceptionCheck()) {
+      // exception thrown from setHandle or descendant
+      env->ExceptionDescribe(); // print out exception to stderr
+    }
+    if(jsStart != nullptr) {
+      env->DeleteLocalRef(jsStart);
+    }
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  }
+
   jstring jsResultStart =
-    (jstring)m_env->CallObjectMethod(m_jComparator,
+    (jstring)env->CallObjectMethod(m_jComparator,
       m_jFindShortestSeparatorMethodId, jsStart, m_jSliceLimit);
 
   mtx_findShortestSeparator->Unlock();
 
-  m_env->DeleteLocalRef(jsStart);
+  if(env->ExceptionCheck()) {
+    // exception thrown from CallObjectMethod
+    env->ExceptionDescribe();  // print out exception to stderr
+    env->DeleteLocalRef(jsStart);
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  }
+
+  env->DeleteLocalRef(jsStart);
 
   if (jsResultStart != nullptr) {
     // update start with result
-    *start =
+    jboolean has_exception = JNI_FALSE;
-      JniUtil::copyString(m_env, jsResultStart);  // also releases jsResultStart
+    std::string result = JniUtil::copyString(env, jsResultStart,
+        &has_exception);  // also releases jsResultStart
+    if (has_exception == JNI_TRUE) {
+      if (env->ExceptionCheck()) {
+        env->ExceptionDescribe();  // print out exception to stderr
+      }
+      JniUtil::releaseJniEnv(m_jvm, attached_thread);
+      return;
+    }
+
+    *start = result;
   }
 
-  m_jvm->DetachCurrentThread();
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
 }
 
 void BaseComparatorJniCallback::FindShortSuccessor(std::string* key) const {
@@ -112,34 +213,69 @@ void BaseComparatorJniCallback::FindShortSuccessor(std::string* key) const {
     return;
   }
 
-  JNIEnv* m_env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
+  assert(env != nullptr);
 
   const char* keyUtf = key->c_str();
-  jstring jsKey = m_env->NewStringUTF(keyUtf);
+  jstring jsKey = env->NewStringUTF(keyUtf);
+  if(jsKey == nullptr) {
+    // unable to construct string
+    if(env->ExceptionCheck()) {
+      env->ExceptionDescribe(); // print out exception to stderr
+    }
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  } else if(env->ExceptionCheck()) {
+    // exception thrown: OutOfMemoryError
+    env->ExceptionDescribe(); // print out exception to stderr
+    env->DeleteLocalRef(jsKey);
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  }
 
   jstring jsResultKey =
-    (jstring)m_env->CallObjectMethod(m_jComparator,
+    (jstring)env->CallObjectMethod(m_jComparator,
       m_jFindShortSuccessorMethodId, jsKey);
 
-  m_env->DeleteLocalRef(jsKey);
+  if(env->ExceptionCheck()) {
+    // exception thrown from CallObjectMethod
+    env->ExceptionDescribe(); // print out exception to stderr
+    env->DeleteLocalRef(jsKey);
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
+    return;
+  }
+
+  env->DeleteLocalRef(jsKey);
 
   if (jsResultKey != nullptr) {
     // updates key with result, also releases jsResultKey.
-    *key = JniUtil::copyString(m_env, jsResultKey);
+    jboolean has_exception = JNI_FALSE;
+    std::string result = JniUtil::copyString(env, jsResultKey, &has_exception);
+    if (has_exception == JNI_TRUE) {
+      if (env->ExceptionCheck()) {
+        env->ExceptionDescribe();  // print out exception to stderr
+      }
+      JniUtil::releaseJniEnv(m_jvm, attached_thread);
+      return;
+    }
+
+    *key = result;
   }
 
-  m_jvm->DetachCurrentThread();
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
 }
 
 BaseComparatorJniCallback::~BaseComparatorJniCallback() {
-  JNIEnv* m_env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
+  assert(env != nullptr);
 
-  m_env->DeleteGlobalRef(m_jComparator);
+  if(m_jComparator != nullptr) {
+    env->DeleteGlobalRef(m_jComparator);
+  }
 
-  // Note: do not need to explicitly detach, as this function is effectively
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
-  // called from the Java class's disposeInternal method, and so already
-  // has an attached thread, getJniEnv above is just a no-op Attach to get
-  // the env jvm->DetachCurrentThread();
 }
 
 ComparatorJniCallback::ComparatorJniCallback(
@@ -147,15 +283,42 @@ ComparatorJniCallback::ComparatorJniCallback(
     const ComparatorJniCallbackOptions* copt) :
     BaseComparatorJniCallback(env, jComparator, copt) {
   m_jSliceA = env->NewGlobalRef(SliceJni::construct0(env));
+  if(m_jSliceA == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   m_jSliceB = env->NewGlobalRef(SliceJni::construct0(env));
+  if(m_jSliceB == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   m_jSliceLimit = env->NewGlobalRef(SliceJni::construct0(env));
+  if(m_jSliceLimit == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 }
 
 ComparatorJniCallback::~ComparatorJniCallback() {
-  JNIEnv* m_env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
-  m_env->DeleteGlobalRef(m_jSliceA);
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
-  m_env->DeleteGlobalRef(m_jSliceB);
+  assert(env != nullptr);
-  m_env->DeleteGlobalRef(m_jSliceLimit);
+
+  if(m_jSliceA != nullptr) {
+    env->DeleteGlobalRef(m_jSliceA);
+  }
+
+  if(m_jSliceB != nullptr) {
+    env->DeleteGlobalRef(m_jSliceB);
+  }
+
+  if(m_jSliceLimit != nullptr) {
+    env->DeleteGlobalRef(m_jSliceLimit);
+  }
+
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
 }
 
 DirectComparatorJniCallback::DirectComparatorJniCallback(
@@ -163,14 +326,41 @@ DirectComparatorJniCallback::DirectComparatorJniCallback(
     const ComparatorJniCallbackOptions* copt) :
     BaseComparatorJniCallback(env, jComparator, copt) {
   m_jSliceA = env->NewGlobalRef(DirectSliceJni::construct0(env));
+  if(m_jSliceA == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   m_jSliceB = env->NewGlobalRef(DirectSliceJni::construct0(env));
+  if(m_jSliceB == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   m_jSliceLimit = env->NewGlobalRef(DirectSliceJni::construct0(env));
+  if(m_jSliceLimit == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 }
 
 DirectComparatorJniCallback::~DirectComparatorJniCallback() {
-  JNIEnv* m_env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
-  m_env->DeleteGlobalRef(m_jSliceA);
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
-  m_env->DeleteGlobalRef(m_jSliceB);
+  assert(env != nullptr);
-  m_env->DeleteGlobalRef(m_jSliceLimit);
+
+  if(m_jSliceA != nullptr) {
+    env->DeleteGlobalRef(m_jSliceA);
+  }
+
+  if(m_jSliceB != nullptr) {
+    env->DeleteGlobalRef(m_jSliceB);
+  }
+
+  if(m_jSliceLimit != nullptr) {
+    env->DeleteGlobalRef(m_jSliceLimit);
+  }
+
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
 }
 }  // namespace rocksdb

java/rocksjni/comparatorjnicallback.h

@@ -61,7 +61,6 @@ class BaseComparatorJniCallback : public Comparator {
     port::Mutex* mtx_compare;
     // used for synchronisation in findShortestSeparator method
     port::Mutex* mtx_findShortestSeparator;
-    JavaVM* m_jvm;
     jobject m_jComparator;
     std::string m_name;
     jmethodID m_jCompareMethodId;
@@ -69,7 +68,7 @@ class BaseComparatorJniCallback : public Comparator {
     jmethodID m_jFindShortSuccessorMethodId;
 
  protected:
-    JNIEnv* getJniEnv() const;
+    JavaVM* m_jvm;
     jobject m_jSliceA;
     jobject m_jSliceB;
     jobject m_jSliceLimit;

java/rocksjni/env.cc

@@ -75,5 +75,7 @@ jlong Java_org_rocksdb_RocksMemEnv_createMemEnv(
  */
 void Java_org_rocksdb_RocksMemEnv_disposeInternal(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  delete reinterpret_cast<rocksdb::Env*>(jhandle);
+  auto* e = reinterpret_cast<rocksdb::Env*>(jhandle);
+  assert(e != nullptr);
+  delete e;
 }

java/rocksjni/env_options.cc

@@ -44,7 +44,9 @@ jlong Java_org_rocksdb_EnvOptions_newEnvOptions(JNIEnv *env, jclass jcls) {
  */
 void Java_org_rocksdb_EnvOptions_disposeInternal(JNIEnv *env, jobject jobj,
                                                  jlong jhandle) {
-  delete reinterpret_cast<rocksdb::EnvOptions *>(jhandle);
+  auto* eo = reinterpret_cast<rocksdb::EnvOptions *>(jhandle);
+  assert(eo != nullptr);
+  delete eo;
 }
 
 /*
@@ -288,7 +290,8 @@ jlong Java_org_rocksdb_EnvOptions_writableFileMaxBufferSize(JNIEnv *env,
 void Java_org_rocksdb_EnvOptions_setRateLimiter(JNIEnv *env, jobject jobj,
                                                 jlong jhandle,
                                                 jlong rl_handle) {
-  auto *rate_limiter = reinterpret_cast<rocksdb::RateLimiter *>(rl_handle);
+  auto* sptr_rate_limiter =
-  auto *env_opt = reinterpret_cast<rocksdb::EnvOptions *>(jhandle);
+      reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(rl_handle);
-  env_opt->rate_limiter = rate_limiter;
+  auto* env_opt = reinterpret_cast<rocksdb::EnvOptions *>(jhandle);
+  env_opt->rate_limiter = sptr_rate_limiter->get();
 }

java/rocksjni/external_sst_file_info.cc

@@ -31,17 +31,35 @@ jlong Java_org_rocksdb_ExternalSstFileInfo_newExternalSstFileInfo__Ljava_lang_St
     JNIEnv *env, jclass jcls, jstring jfile_path, jstring jsmallest_key,
     jstring jlargest_key, jlong jsequence_number, jlong jfile_size,
     jint jnum_entries, jint jversion) {
-  const char *file_path = env->GetStringUTFChars(jfile_path, NULL);
+  const char *file_path = env->GetStringUTFChars(jfile_path, nullptr);
-  const char *smallest_key = env->GetStringUTFChars(jsmallest_key, NULL);
+  if(file_path == nullptr) {
-  const char *largest_key = env->GetStringUTFChars(jlargest_key, NULL);
+    // exception thrown: OutOfMemoryError
+    return 0;
+  }
+  const char *smallest_key = env->GetStringUTFChars(jsmallest_key, nullptr);
+  if(smallest_key == nullptr) {
+    // exception thrown: OutOfMemoryError
+    env->ReleaseStringUTFChars(jfile_path, file_path);
+    return 0;
+  }
+  const char *largest_key = env->GetStringUTFChars(jlargest_key, nullptr);
+  if(largest_key == nullptr) {
+    // exception thrown: OutOfMemoryError
+    env->ReleaseStringUTFChars(jsmallest_key, smallest_key);
+    env->ReleaseStringUTFChars(jfile_path, file_path);
+    return 0;
+  }
+
   auto *external_sst_file_info = new rocksdb::ExternalSstFileInfo(
       file_path, smallest_key, largest_key,
       static_cast<rocksdb::SequenceNumber>(jsequence_number),
       static_cast<uint64_t>(jfile_size), static_cast<int32_t>(jnum_entries),
       static_cast<int32_t>(jversion));
-  env->ReleaseStringUTFChars(jfile_path, file_path);
+
-  env->ReleaseStringUTFChars(jsmallest_key, smallest_key);
   env->ReleaseStringUTFChars(jlargest_key, largest_key);
+  env->ReleaseStringUTFChars(jsmallest_key, smallest_key);
+  env->ReleaseStringUTFChars(jfile_path, file_path);
+
   return reinterpret_cast<jlong>(external_sst_file_info);
 }
 
@@ -55,7 +73,11 @@ void Java_org_rocksdb_ExternalSstFileInfo_setFilePath(JNIEnv *env, jobject jobj,
                                                       jstring jfile_path) {
   auto *external_sst_file_info =
       reinterpret_cast<rocksdb::ExternalSstFileInfo *>(jhandle);
-  const char *file_path = env->GetStringUTFChars(jfile_path, NULL);
+  const char *file_path = env->GetStringUTFChars(jfile_path, nullptr);
+  if(file_path == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   external_sst_file_info->file_path = file_path;
   env->ReleaseStringUTFChars(jfile_path, file_path);
 }
@@ -81,7 +103,11 @@ void Java_org_rocksdb_ExternalSstFileInfo_setSmallestKey(
     JNIEnv *env, jobject jobj, jlong jhandle, jstring jsmallest_key) {
   auto *external_sst_file_info =
       reinterpret_cast<rocksdb::ExternalSstFileInfo *>(jhandle);
-  const char *smallest_key = env->GetStringUTFChars(jsmallest_key, NULL);
+  const char *smallest_key = env->GetStringUTFChars(jsmallest_key, nullptr);
+  if(smallest_key == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   external_sst_file_info->smallest_key = smallest_key;
   env->ReleaseStringUTFChars(jsmallest_key, smallest_key);
 }
@@ -111,6 +137,10 @@ void Java_org_rocksdb_ExternalSstFileInfo_setLargestKey(JNIEnv *env,
   auto *external_sst_file_info =
       reinterpret_cast<rocksdb::ExternalSstFileInfo *>(jhandle);
   const char *largest_key = env->GetStringUTFChars(jlargest_key, NULL);
+  if(largest_key == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   external_sst_file_info->largest_key = largest_key;
   env->ReleaseStringUTFChars(jlargest_key, largest_key);
 }
@@ -238,5 +268,7 @@ jint Java_org_rocksdb_ExternalSstFileInfo_version(JNIEnv *env, jobject jobj,
 void Java_org_rocksdb_ExternalSstFileInfo_disposeInternal(JNIEnv *env,
                                                           jobject jobj,
                                                           jlong jhandle) {
-  delete reinterpret_cast<rocksdb::ExternalSstFileInfo *>(jhandle);
+  auto* esfi = reinterpret_cast<rocksdb::ExternalSstFileInfo *>(jhandle);
+  assert(esfi != nullptr);
+  delete esfi;
 }

java/rocksjni/filter.cc

@@ -24,12 +24,10 @@
 jlong Java_org_rocksdb_BloomFilter_createNewBloomFilter(
     JNIEnv* env, jclass jcls, jint bits_per_key,
     jboolean use_block_base_builder) {
-  auto* fp = const_cast<rocksdb::FilterPolicy *>(
+  auto* sptr_filter =
-      rocksdb::NewBloomFilterPolicy(bits_per_key, use_block_base_builder));
+      new std::shared_ptr<const rocksdb::FilterPolicy>(
-  auto* pFilterPolicy =
+          rocksdb::NewBloomFilterPolicy(bits_per_key, use_block_base_builder));
-      new std::shared_ptr<rocksdb::FilterPolicy>;
+  return reinterpret_cast<jlong>(sptr_filter);
-  *pFilterPolicy = std::shared_ptr<rocksdb::FilterPolicy>(fp);
-  return reinterpret_cast<jlong>(pFilterPolicy);
 }
 
 /*
@@ -39,8 +37,7 @@ jlong Java_org_rocksdb_BloomFilter_createNewBloomFilter(
  */
 void Java_org_rocksdb_Filter_disposeInternal(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-
+  auto* handle =
-  std::shared_ptr<rocksdb::FilterPolicy> *handle =
+      reinterpret_cast<std::shared_ptr<const rocksdb::FilterPolicy> *>(jhandle);
-      reinterpret_cast<std::shared_ptr<rocksdb::FilterPolicy> *>(jhandle);
+  delete handle;  // delete std::shared_ptr
-  handle->reset();
 }

java/rocksjni/iterator.cc

@@ -21,7 +21,8 @@
  */
 void Java_org_rocksdb_RocksIterator_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  auto it = reinterpret_cast<rocksdb::Iterator*>(handle);
+  auto* it = reinterpret_cast<rocksdb::Iterator*>(handle);
+  assert(it != nullptr);
   delete it;
 }
 
@@ -83,11 +84,16 @@ void Java_org_rocksdb_RocksIterator_prev0(
 void Java_org_rocksdb_RocksIterator_seek0(
     JNIEnv* env, jobject jobj, jlong handle,
     jbyteArray jtarget, jint jtarget_len) {
-  auto it = reinterpret_cast<rocksdb::Iterator*>(handle);
+  jbyte* target = env->GetByteArrayElements(jtarget, nullptr);
-  jbyte* target = env->GetByteArrayElements(jtarget, 0);
+  if(target == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   rocksdb::Slice target_slice(
       reinterpret_cast<char*>(target), jtarget_len);
 
+  auto* it = reinterpret_cast<rocksdb::Iterator*>(handle);
   it->Seek(target_slice);
 
   env->ReleaseByteArrayElements(jtarget, target, JNI_ABORT);
@@ -100,7 +106,7 @@ void Java_org_rocksdb_RocksIterator_seek0(
  */
 void Java_org_rocksdb_RocksIterator_status0(
     JNIEnv* env, jobject jobj, jlong handle) {
-  auto it = reinterpret_cast<rocksdb::Iterator*>(handle);
+  auto* it = reinterpret_cast<rocksdb::Iterator*>(handle);
   rocksdb::Status s = it->status();
 
   if (s.ok()) {
@@ -117,10 +123,14 @@ void Java_org_rocksdb_RocksIterator_status0(
  */
 jbyteArray Java_org_rocksdb_RocksIterator_key0(
     JNIEnv* env, jobject jobj, jlong handle) {
-  auto it = reinterpret_cast<rocksdb::Iterator*>(handle);
+  auto* it = reinterpret_cast<rocksdb::Iterator*>(handle);
   rocksdb::Slice key_slice = it->key();
 
   jbyteArray jkey = env->NewByteArray(static_cast<jsize>(key_slice.size()));
+  if(jkey == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return nullptr;
+  }
   env->SetByteArrayRegion(jkey, 0, static_cast<jsize>(key_slice.size()),
                           reinterpret_cast<const jbyte*>(key_slice.data()));
   return jkey;
@@ -133,11 +143,15 @@ jbyteArray Java_org_rocksdb_RocksIterator_key0(
  */
 jbyteArray Java_org_rocksdb_RocksIterator_value0(
     JNIEnv* env, jobject jobj, jlong handle) {
-  auto it = reinterpret_cast<rocksdb::Iterator*>(handle);
+  auto* it = reinterpret_cast<rocksdb::Iterator*>(handle);
   rocksdb::Slice value_slice = it->value();
 
   jbyteArray jkeyValue =
       env->NewByteArray(static_cast<jsize>(value_slice.size()));
+  if(jkeyValue == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return nullptr;
+  }
   env->SetByteArrayRegion(jkeyValue, 0, static_cast<jsize>(value_slice.size()),
                           reinterpret_cast<const jbyte*>(value_slice.data()));
   return jkeyValue;

java/rocksjni/loggerjnicallback.cc

@@ -10,53 +10,106 @@
 
 #include "rocksjni/loggerjnicallback.h"
 #include "rocksjni/portal.h"
+#include <cstdarg>
+#include <cstdio>
 
 namespace rocksdb {
 
 LoggerJniCallback::LoggerJniCallback(
     JNIEnv* env, jobject jlogger) {
-  const jint rs __attribute__((unused)) = env->GetJavaVM(&m_jvm);
+  // Note: Logger methods may be accessed by multiple threads,
-  assert(rs == JNI_OK);
+  // so we ref the jvm not the env
+  const jint rs = env->GetJavaVM(&m_jvm);
+  if(rs != JNI_OK) {
+    // exception thrown
+    return;
+  }
 
   // Note: we want to access the Java Logger instance
   // across multiple method calls, so we create a global ref
+  assert(jlogger != nullptr);
   m_jLogger = env->NewGlobalRef(jlogger);
+  if(m_jLogger == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   m_jLogMethodId = LoggerJni::getLogMethodId(env);
+  if(m_jLogMethodId == nullptr) {
+    // exception thrown: NoSuchMethodException or OutOfMemoryError
+    return;
+  }
 
   jobject jdebug_level = InfoLogLevelJni::DEBUG_LEVEL(env);
-  assert(jdebug_level != nullptr);
+  if(jdebug_level == nullptr) {
+    // exception thrown: NoSuchFieldError, ExceptionInInitializerError
+    // or OutOfMemoryError
+    return;
+  }
   m_jdebug_level = env->NewGlobalRef(jdebug_level);
+  if(m_jdebug_level == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   jobject jinfo_level = InfoLogLevelJni::INFO_LEVEL(env);
-  assert(jinfo_level != nullptr);
+  if(jinfo_level == nullptr) {
+    // exception thrown: NoSuchFieldError, ExceptionInInitializerError
+    // or OutOfMemoryError
+    return;
+  }
   m_jinfo_level = env->NewGlobalRef(jinfo_level);
+  if(m_jinfo_level == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   jobject jwarn_level = InfoLogLevelJni::WARN_LEVEL(env);
-  assert(jwarn_level != nullptr);
+  if(jwarn_level == nullptr) {
+    // exception thrown: NoSuchFieldError, ExceptionInInitializerError
+    // or OutOfMemoryError
+    return;
+  }
   m_jwarn_level = env->NewGlobalRef(jwarn_level);
+  if(m_jwarn_level == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   jobject jerror_level = InfoLogLevelJni::ERROR_LEVEL(env);
-  assert(jerror_level != nullptr);
+  if(jerror_level == nullptr) {
+    // exception thrown: NoSuchFieldError, ExceptionInInitializerError
+    // or OutOfMemoryError
+    return;
+  }
   m_jerror_level = env->NewGlobalRef(jerror_level);
+  if(m_jerror_level == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   jobject jfatal_level = InfoLogLevelJni::FATAL_LEVEL(env);
-  assert(jfatal_level != nullptr);
+  if(jfatal_level == nullptr) {
+    // exception thrown: NoSuchFieldError, ExceptionInInitializerError
+    // or OutOfMemoryError
+    return;
+  }
   m_jfatal_level = env->NewGlobalRef(jfatal_level);
+  if(m_jfatal_level == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   jobject jheader_level = InfoLogLevelJni::HEADER_LEVEL(env);
-  assert(jheader_level != nullptr);
+  if(jheader_level == nullptr) {
+    // exception thrown: NoSuchFieldError, ExceptionInInitializerError
+    // or OutOfMemoryError
+    return;
+  }
   m_jheader_level = env->NewGlobalRef(jheader_level);
-}
+  if(m_jheader_level == nullptr) {
-
+    // exception thrown: OutOfMemoryError
-/**
+    return;
- * Get JNIEnv for current native thread
+  }
- */
-JNIEnv* LoggerJniCallback::getJniEnv() const {
-  JNIEnv *env;
-  jint rs __attribute__((unused)) =
-      m_jvm->AttachCurrentThread(reinterpret_cast<void**>(&env), NULL);
-  assert(rs == JNI_OK);
-  return env;
 }
 
 void LoggerJniCallback::Logv(const char* format, va_list ap) {
@@ -94,69 +147,96 @@ void LoggerJniCallback::Logv(const InfoLogLevel log_level,
         break;
     }
 
-    // We try twice: the first time with a fixed-size stack allocated buffer,
+    assert(format != nullptr);
-    // and the second time with a much larger dynamically allocated buffer.
+    assert(ap != nullptr);
-    char buffer[500];
+    const std::unique_ptr<char[]> msg = format_str(format, ap);
-    for (int iter = 0; iter < 2; iter++) {
-      char* base;
-      int bufsize;
-      if (iter == 0) {
-        bufsize = sizeof(buffer);
-        base = buffer;
-      } else {
-        bufsize = 30000;
-        base = new char[bufsize];
-      }
-      char* p = base;
-      char* limit = base + bufsize;
-      // Print the message
-      if (p < limit) {
-        va_list backup_ap;
-        va_copy(backup_ap, ap);
-        p += vsnprintf(p, limit - p, format, backup_ap);
-        va_end(backup_ap);
-      }
-      // Truncate to available space if necessary
-      if (p >= limit) {
-        if (iter == 0) {
-          continue;       // Try again with larger buffer
-        } else {
-          p = limit - 1;
-        }
-      }
-      assert(p < limit);
-      *p++ = '\0';
-
-      JNIEnv* env = getJniEnv();
 
-      // pass java string to callback handler
+    // pass msg to java callback handler
-      env->CallVoidMethod(
+    jboolean attached_thread = JNI_FALSE;
-          m_jLogger,
+    JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
-          m_jLogMethodId,
+    assert(env != nullptr);
-          jlog_level,
-          env->NewStringUTF(base));
 
-      if (base != buffer) {
+    jstring jmsg = env->NewStringUTF(msg.get());
-        delete[] base;
+    if(jmsg == nullptr) {
+      // unable to construct string
+      if(env->ExceptionCheck()) {
+        env->ExceptionDescribe(); // print out exception to stderr
       }
-      break;
+      JniUtil::releaseJniEnv(m_jvm, attached_thread);
+      return;
+    }
+    if(env->ExceptionCheck()) {
+      // exception thrown: OutOfMemoryError
+      env->ExceptionDescribe(); // print out exception to stderr
+      env->DeleteLocalRef(jmsg);
+      JniUtil::releaseJniEnv(m_jvm, attached_thread);
+      return;
+    }
+
+    env->CallVoidMethod(m_jLogger, m_jLogMethodId, jlog_level, jmsg);
+    if(env->ExceptionCheck()) {
+      // exception thrown
+      env->ExceptionDescribe(); // print out exception to stderr
+      env->DeleteLocalRef(jmsg);
+      JniUtil::releaseJniEnv(m_jvm, attached_thread);
+      return;
     }
-    m_jvm->DetachCurrentThread();
+
+    env->DeleteLocalRef(jmsg);
+    JniUtil::releaseJniEnv(m_jvm, attached_thread);
   }
 }
 
+std::unique_ptr<char[]> LoggerJniCallback::format_str(const char* format, va_list ap) const {
+  va_list ap_copy;
+
+  va_copy(ap_copy, ap);
+  const size_t required = vsnprintf(nullptr, 0, format, ap_copy) + 1; // Extra space for '\0'
+  va_end(ap_copy);
+
+  std::unique_ptr<char[]> buf(new char[required]);
+
+  va_copy(ap_copy, ap);
+  vsnprintf(buf.get(), required, format, ap_copy);
+  va_end(ap_copy);
+
+  return buf;
+}
+
 LoggerJniCallback::~LoggerJniCallback() {
-  JNIEnv* env = getJniEnv();
+  jboolean attached_thread = JNI_FALSE;
-  env->DeleteGlobalRef(m_jLogger);
+  JNIEnv* env = JniUtil::getJniEnv(m_jvm, &attached_thread);
+  assert(env != nullptr);
+
+  if(m_jLogger != nullptr) {
+    env->DeleteGlobalRef(m_jLogger);
+  }
+
+  if(m_jdebug_level != nullptr) {
+    env->DeleteGlobalRef(m_jdebug_level);
+  }
+
+  if(m_jinfo_level != nullptr) {
+    env->DeleteGlobalRef(m_jinfo_level);
+  }
+
+  if(m_jwarn_level != nullptr) {
+    env->DeleteGlobalRef(m_jwarn_level);
+  }
+
+  if(m_jerror_level != nullptr) {
+    env->DeleteGlobalRef(m_jerror_level);
+  }
+
+  if(m_jfatal_level != nullptr) {
+    env->DeleteGlobalRef(m_jfatal_level);
+  }
 
-  env->DeleteGlobalRef(m_jdebug_level);
+  if(m_jheader_level != nullptr) {
-  env->DeleteGlobalRef(m_jinfo_level);
+    env->DeleteGlobalRef(m_jheader_level);
-  env->DeleteGlobalRef(m_jwarn_level);
+  }
-  env->DeleteGlobalRef(m_jerror_level);
-  env->DeleteGlobalRef(m_jfatal_level);
-  env->DeleteGlobalRef(m_jheader_level);
 
-  m_jvm->DetachCurrentThread();
+  JniUtil::releaseJniEnv(m_jvm, attached_thread);
 }
 
 }  // namespace rocksdb
@@ -168,15 +248,14 @@ LoggerJniCallback::~LoggerJniCallback() {
  */
 jlong Java_org_rocksdb_Logger_createNewLoggerOptions(
     JNIEnv* env, jobject jobj, jlong joptions) {
-  rocksdb::LoggerJniCallback* c =
+  auto* sptr_logger = new std::shared_ptr<rocksdb::LoggerJniCallback>(
-      new rocksdb::LoggerJniCallback(env, jobj);
+      new rocksdb::LoggerJniCallback(env, jobj));
+
   // set log level
-  c->SetInfoLogLevel(reinterpret_cast<rocksdb::Options*>
+  auto* options = reinterpret_cast<rocksdb::Options*>(joptions);
-      (joptions)->info_log_level);
+  sptr_logger->get()->SetInfoLogLevel(options->info_log_level);
-  std::shared_ptr<rocksdb::LoggerJniCallback> *pLoggerJniCallback =
+
-      new std::shared_ptr<rocksdb::LoggerJniCallback>;
+  return reinterpret_cast<jlong>(sptr_logger);
-  *pLoggerJniCallback = std::shared_ptr<rocksdb::LoggerJniCallback>(c);
-  return reinterpret_cast<jlong>(pLoggerJniCallback);
 }
 
 /*
@@ -186,15 +265,14 @@ jlong Java_org_rocksdb_Logger_createNewLoggerOptions(
  */
 jlong Java_org_rocksdb_Logger_createNewLoggerDbOptions(
     JNIEnv* env, jobject jobj, jlong jdb_options) {
-  rocksdb::LoggerJniCallback* c =
+  auto* sptr_logger = new std::shared_ptr<rocksdb::LoggerJniCallback>(
-      new rocksdb::LoggerJniCallback(env, jobj);
+    new rocksdb::LoggerJniCallback(env, jobj));
+
   // set log level
-  c->SetInfoLogLevel(reinterpret_cast<rocksdb::DBOptions*>
+  auto* db_options = reinterpret_cast<rocksdb::DBOptions*>(jdb_options);
-      (jdb_options)->info_log_level);
+  sptr_logger->get()->SetInfoLogLevel(db_options->info_log_level);
-  std::shared_ptr<rocksdb::LoggerJniCallback> *pLoggerJniCallback =
+
-      new std::shared_ptr<rocksdb::LoggerJniCallback>;
+  return reinterpret_cast<jlong>(sptr_logger);
-  *pLoggerJniCallback = std::shared_ptr<rocksdb::LoggerJniCallback>(c);
-  return reinterpret_cast<jlong>(pLoggerJniCallback);
 }
 
 /*
@@ -204,9 +282,10 @@ jlong Java_org_rocksdb_Logger_createNewLoggerDbOptions(
  */
 void Java_org_rocksdb_Logger_setInfoLogLevel(
     JNIEnv* env, jobject jobj, jlong jhandle, jbyte jlog_level) {
-  std::shared_ptr<rocksdb::LoggerJniCallback> *handle =
+  auto* handle =
       reinterpret_cast<std::shared_ptr<rocksdb::LoggerJniCallback> *>(jhandle);
-  (*handle)->SetInfoLogLevel(static_cast<rocksdb::InfoLogLevel>(jlog_level));
+  handle->get()->
+      SetInfoLogLevel(static_cast<rocksdb::InfoLogLevel>(jlog_level));
 }
 
 /*
@@ -216,9 +295,9 @@ void Java_org_rocksdb_Logger_setInfoLogLevel(
  */
 jbyte Java_org_rocksdb_Logger_infoLogLevel(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  std::shared_ptr<rocksdb::LoggerJniCallback> *handle =
+  auto* handle =
       reinterpret_cast<std::shared_ptr<rocksdb::LoggerJniCallback> *>(jhandle);
-  return static_cast<jbyte>((*handle)->GetInfoLogLevel());
+  return static_cast<jbyte>(handle->get()->GetInfoLogLevel());
 }
 
 /*
@@ -228,7 +307,7 @@ jbyte Java_org_rocksdb_Logger_infoLogLevel(
  */
 void Java_org_rocksdb_Logger_disposeInternal(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  std::shared_ptr<rocksdb::LoggerJniCallback> *handle =
+  auto* handle =
       reinterpret_cast<std::shared_ptr<rocksdb::LoggerJniCallback> *>(jhandle);
-  handle->reset();
+  delete handle;  // delete std::shared_ptr
 }

java/rocksjni/loggerjnicallback.h

@@ -10,6 +10,7 @@
 #define JAVA_ROCKSJNI_LOGGERJNICALLBACK_H_
 
 #include <jni.h>
+#include <memory>
 #include <string>
 #include "port/port.h"
 #include "rocksdb/env.h"
@@ -32,8 +33,6 @@ namespace rocksdb {
      virtual void Logv(const InfoLogLevel log_level,
          const char* format, va_list ap);
 
-   protected:
-     JNIEnv* getJniEnv() const;
    private:
      JavaVM* m_jvm;
      jobject m_jLogger;
@@ -44,6 +43,7 @@ namespace rocksdb {
      jobject m_jerror_level;
      jobject m_jfatal_level;
      jobject m_jheader_level;
+     std::unique_ptr<char[]> format_str(const char* format, va_list ap) const;
   };
 }  // namespace rocksdb
 

java/rocksjni/merge_operator.cc

@@ -25,13 +25,24 @@
 
 /*
  * Class:     org_rocksdb_StringAppendOperator
- * Method:    newMergeOperatorHandle
+ * Method:    newSharedStringAppendOperator
  * Signature: ()J
  */
-jlong Java_org_rocksdb_StringAppendOperator_newMergeOperatorHandleImpl
+jlong Java_org_rocksdb_StringAppendOperator_newSharedStringAppendOperator
-(JNIEnv* env, jobject jobj) {
+(JNIEnv* env, jclass jclazz) {
-  std::shared_ptr<rocksdb::MergeOperator> *op =
+  auto* sptr_string_append_op = new std::shared_ptr<rocksdb::MergeOperator>(
-    new std::shared_ptr<rocksdb::MergeOperator>();
+    rocksdb::MergeOperators::CreateFromStringId("stringappend"));
-  *op = rocksdb::MergeOperators::CreateFromStringId("stringappend");
+  return reinterpret_cast<jlong>(sptr_string_append_op);
-  return reinterpret_cast<jlong>(op);
+}
+
+/*
+ * Class:     org_rocksdb_StringAppendOperator
+ * Method:    disposeInternal
+ * Signature: (J)V
+ */
+void Java_org_rocksdb_StringAppendOperator_disposeInternal(
+    JNIEnv* env, jobject jobj, jlong jhandle) {
+  auto* sptr_string_append_op =
+      reinterpret_cast<std::shared_ptr<rocksdb::MergeOperator>* >(jhandle);
+  delete sptr_string_append_op;  // delete std::shared_ptr
 }

java/rocksjni/options.cc

@@ -39,7 +39,7 @@
  * Signature: ()J
  */
 jlong Java_org_rocksdb_Options_newOptions__(JNIEnv* env, jclass jcls) {
-  rocksdb::Options* op = new rocksdb::Options();
+  auto* op = new rocksdb::Options();
   return reinterpret_cast<jlong>(op);
 }
 
@@ -53,7 +53,7 @@ jlong Java_org_rocksdb_Options_newOptions__JJ(JNIEnv* env, jclass jcls,
   auto* dbOpt = reinterpret_cast<const rocksdb::DBOptions*>(jdboptions);
   auto* cfOpt = reinterpret_cast<const rocksdb::ColumnFamilyOptions*>(
       jcfoptions);
-  rocksdb::Options* op = new rocksdb::Options(*dbOpt, *cfOpt);
+  auto* op = new rocksdb::Options(*dbOpt, *cfOpt);
   return reinterpret_cast<jlong>(op);
 }
 
@@ -64,7 +64,9 @@ jlong Java_org_rocksdb_Options_newOptions__JJ(JNIEnv* env, jclass jcls,
  */
 void Java_org_rocksdb_Options_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::Options*>(handle);
+  auto* op = reinterpret_cast<rocksdb::Options*>(handle);
+  assert(op != nullptr);
+  delete op;
 }
 
 /*
@@ -157,10 +159,16 @@ void Java_org_rocksdb_Options_setComparatorHandle__JJ(
  */
 void Java_org_rocksdb_Options_setMergeOperatorName(
     JNIEnv* env, jobject jobj, jlong jhandle, jstring jop_name) {
-  auto options = reinterpret_cast<rocksdb::Options*>(jhandle);
+  const char* op_name = env->GetStringUTFChars(jop_name, nullptr);
-  const char* op_name = env->GetStringUTFChars(jop_name, 0);
+  if(op_name == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
+  auto* options = reinterpret_cast<rocksdb::Options*>(jhandle);
   options->merge_operator = rocksdb::MergeOperators::CreateFromStringId(
         op_name);
+
   env->ReleaseStringUTFChars(jop_name, op_name);
 }
 
@@ -231,7 +239,7 @@ void Java_org_rocksdb_Options_createStatistics(
  */
 jlong Java_org_rocksdb_Options_statisticsPtr(
     JNIEnv* env, jobject jobj, jlong jOptHandle) {
-  auto st = reinterpret_cast<rocksdb::Options*>(jOptHandle)->statistics.get();
+  auto* st = reinterpret_cast<rocksdb::Options*>(jOptHandle)->statistics.get();
   return reinterpret_cast<jlong>(st);
 }
 
@@ -381,7 +389,11 @@ jstring Java_org_rocksdb_Options_dbLogDir(
  */
 void Java_org_rocksdb_Options_setDbLogDir(
     JNIEnv* env, jobject jobj, jlong jhandle, jstring jdb_log_dir) {
-  const char* log_dir = env->GetStringUTFChars(jdb_log_dir, 0);
+  const char* log_dir = env->GetStringUTFChars(jdb_log_dir, nullptr);
+  if(log_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   reinterpret_cast<rocksdb::Options*>(jhandle)->db_log_dir.assign(log_dir);
   env->ReleaseStringUTFChars(jdb_log_dir, log_dir);
 }
@@ -404,7 +416,11 @@ jstring Java_org_rocksdb_Options_walDir(
  */
 void Java_org_rocksdb_Options_setWalDir(
     JNIEnv* env, jobject jobj, jlong jhandle, jstring jwal_dir) {
-  const char* wal_dir = env->GetStringUTFChars(jwal_dir, 0);
+  const char* wal_dir = env->GetStringUTFChars(jwal_dir, nullptr);
+  if(wal_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   reinterpret_cast<rocksdb::Options*>(jhandle)->wal_dir.assign(wal_dir);
   env->ReleaseStringUTFChars(jwal_dir, wal_dir);
 }
@@ -494,8 +510,7 @@ void Java_org_rocksdb_Options_setMaxSubcompactions(
  */
 jint Java_org_rocksdb_Options_maxSubcompactions(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  return reinterpret_cast<rocksdb::Options*>(jhandle)
+  return reinterpret_cast<rocksdb::Options*>(jhandle)->max_subcompactions;
-      ->max_subcompactions;
 }
 
 /*
@@ -641,7 +656,7 @@ jlong Java_org_rocksdb_Options_maxManifestFileSize(
  */
 jstring Java_org_rocksdb_Options_memTableFactoryName(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto opt = reinterpret_cast<rocksdb::Options*>(jhandle);
+  auto* opt = reinterpret_cast<rocksdb::Options*>(jhandle);
   rocksdb::MemTableRepFactory* tf = opt->memtable_factory.get();
 
   // Should never be nullptr.
@@ -677,17 +692,6 @@ void Java_org_rocksdb_Options_setMemTableFactory(
       reinterpret_cast<rocksdb::MemTableRepFactory*>(jfactory_handle));
 }
 
-/*
- * Class:     org_rocksdb_Options
- * Method:    setOldRateLimiter
- * Signature: (JJ)V
- */
-void Java_org_rocksdb_Options_setOldRateLimiter(
-    JNIEnv* env, jobject jobj, jlong jhandle, jlong jrate_limiter_handle) {
-  reinterpret_cast<rocksdb::Options*>(jhandle)->rate_limiter.reset(
-      reinterpret_cast<rocksdb::RateLimiter*>(jrate_limiter_handle));
-}
-
 /*
  * Class:     org_rocksdb_Options
  * Method:    setRateLimiter
@@ -1144,7 +1148,7 @@ jlong Java_org_rocksdb_Options_writeThreadSlowYieldUsec(
  */
 jstring Java_org_rocksdb_Options_tableFactoryName(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto opt = reinterpret_cast<rocksdb::Options*>(jhandle);
+  auto* opt = reinterpret_cast<rocksdb::Options*>(jhandle);
   rocksdb::TableFactory* tf = opt->table_factory.get();
 
   // Should never be nullptr.
@@ -1224,46 +1228,78 @@ jbyte Java_org_rocksdb_Options_compressionType(
   return reinterpret_cast<rocksdb::Options*>(jhandle)->compression;
 }
 
-/*
+/**
- * Helper method to convert a Java list to a CompressionType
+ * Helper method to convert a Java byte array of compression levels
- * vector.
+ * to a C++ vector of rocksdb::CompressionType
- */
+ *
-std::vector<rocksdb::CompressionType> rocksdb_compression_vector_helper(
+ * @param env A pointer to the Java environment
-    JNIEnv* env, jbyteArray jcompressionLevels) {
+ * @param jcompression_levels A reference to a java byte array
-  std::vector<rocksdb::CompressionType> compressionLevels;
+ *     where each byte indicates a compression level
+ *
+ * @return A unique_ptr to the vector, or unique_ptr(nullptr) if a JNI exception occurs
+ */
+std::unique_ptr<std::vector<rocksdb::CompressionType>> rocksdb_compression_vector_helper(
+    JNIEnv* env, jbyteArray jcompression_levels) {
+  jsize len = env->GetArrayLength(jcompression_levels);
+  jbyte* jcompression_level =
+      env->GetByteArrayElements(jcompression_levels, nullptr);
+  if(jcompression_level == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return std::unique_ptr<std::vector<rocksdb::CompressionType>>();
+  }
+
+  auto* compression_levels = new std::vector<rocksdb::CompressionType>();
+  std::unique_ptr<std::vector<rocksdb::CompressionType>> uptr_compression_levels(compression_levels);
 
-  jsize len = env->GetArrayLength(jcompressionLevels);
+  for(jsize i = 0; i < len; i++) {
-  jbyte* jcompressionLevel = env->GetByteArrayElements(jcompressionLevels,
+    jbyte jcl = jcompression_level[i];
-    NULL);
+    compression_levels->push_back(static_cast<rocksdb::CompressionType>(jcl));
-  for(int i = 0; i < len; i++) {
-    jbyte jcl;
-    jcl = jcompressionLevel[i];
-    compressionLevels.push_back(static_cast<rocksdb::CompressionType>(jcl));
   }
-  env->ReleaseByteArrayElements(jcompressionLevels, jcompressionLevel,
+
+  env->ReleaseByteArrayElements(jcompression_levels, jcompression_level,
       JNI_ABORT);
 
-  return compressionLevels;
+  return uptr_compression_levels;
 }
 
-/*
+/**
- * Helper method to convert a CompressionType vector to a Java
+ * Helper method to convert a C++ vector of rocksdb::CompressionType
- * List.
+ * to a Java byte array of compression levels
+ *
+ * @param env A pointer to the Java environment
+ * @param jcompression_levels A reference to a java byte array
+ *     where each byte indicates a compression level
+ *
+ * @return A jbytearray or nullptr if an exception occurs
  */
 jbyteArray rocksdb_compression_list_helper(JNIEnv* env,
-    std::vector<rocksdb::CompressionType> compressionLevels) {
+    std::vector<rocksdb::CompressionType> compression_levels) {
-  std::unique_ptr<jbyte[]> jbuf =
+  const size_t len = compression_levels.size();
-      std::unique_ptr<jbyte[]>(new jbyte[compressionLevels.size()]);
+  jbyte* jbuf = new jbyte[len];
-  for (std::vector<rocksdb::CompressionType>::size_type i = 0;
+
-        i != compressionLevels.size(); i++) {
+  for (size_t i = 0; i < len; i++) {
-      jbuf[i] = compressionLevels[i];
+      jbuf[i] = compression_levels[i];
   }
+
   // insert in java array
-  jbyteArray jcompressionLevels = env->NewByteArray(
+  jbyteArray jcompression_levels = env->NewByteArray(static_cast<jsize>(len));
-      static_cast<jsize>(compressionLevels.size()));
+  if(jcompression_levels == nullptr) {
-  env->SetByteArrayRegion(jcompressionLevels, 0,
+      // exception thrown: OutOfMemoryError
-      static_cast<jsize>(compressionLevels.size()), jbuf.get());
+      delete [] jbuf;
-  return jcompressionLevels;
+      return nullptr;
+  }
+  env->SetByteArrayRegion(jcompression_levels, 0, static_cast<jsize>(len),
+      jbuf);
+  if(env->ExceptionCheck()) {
+      // exception thrown: ArrayIndexOutOfBoundsException
+      env->DeleteLocalRef(jcompression_levels);
+      delete [] jbuf;
+      return nullptr;
+  }
+
+  delete [] jbuf;
+
+  return jcompression_levels;
 }
 
 /*
@@ -1274,10 +1310,14 @@ jbyteArray rocksdb_compression_list_helper(JNIEnv* env,
 void Java_org_rocksdb_Options_setCompressionPerLevel(
     JNIEnv* env, jobject jobj, jlong jhandle,
     jbyteArray jcompressionLevels) {
-  auto* options = reinterpret_cast<rocksdb::Options*>(jhandle);
+  auto uptr_compression_levels =
-  std::vector<rocksdb::CompressionType> compressionLevels =
       rocksdb_compression_vector_helper(env, jcompressionLevels);
-  options->compression_per_level = compressionLevels;
+  if(!uptr_compression_levels) {
+    // exception occurred
+    return;
+  }
+  auto* options = reinterpret_cast<rocksdb::Options*>(jhandle);
+  options->compression_per_level = *(uptr_compression_levels.get());
 }
 
 /*
@@ -1946,7 +1986,6 @@ jlong Java_org_rocksdb_Options_memtableHugePageSize(
 void Java_org_rocksdb_Options_setMemtableHugePageSize(
     JNIEnv* env, jobject jobj, jlong jhandle,
     jlong jmemtable_huge_page_size) {
-
   rocksdb::Status s = rocksdb::check_if_jlong_fits_size_t(
       jmemtable_huge_page_size);
   if (s.ok()) {
@@ -2083,8 +2122,9 @@ void Java_org_rocksdb_Options_setLevel0StopWritesTrigger(
  */
 jintArray Java_org_rocksdb_Options_maxBytesForLevelMultiplierAdditional(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto mbflma = reinterpret_cast<rocksdb::Options*>(
+  auto mbflma =
-      jhandle)->max_bytes_for_level_multiplier_additional;
+      reinterpret_cast<rocksdb::Options*>(jhandle)->
+          max_bytes_for_level_multiplier_additional;
 
   const size_t size = mbflma.size();
 
@@ -2095,7 +2135,19 @@ jintArray Java_org_rocksdb_Options_maxBytesForLevelMultiplierAdditional(
 
   jsize jlen = static_cast<jsize>(size);
   jintArray result = env->NewIntArray(jlen);
+  if(result == nullptr) {
+      // exception thrown: OutOfMemoryError
+      delete [] additionals;
+      return nullptr;
+  }
+
   env->SetIntArrayRegion(result, 0, jlen, additionals);
+  if(env->ExceptionCheck()) {
+      // exception thrown: ArrayIndexOutOfBoundsException
+      env->DeleteLocalRef(result);
+      delete [] additionals;
+      return nullptr;
+  }
 
   delete [] additionals;
 
@@ -2112,12 +2164,20 @@ void Java_org_rocksdb_Options_setMaxBytesForLevelMultiplierAdditional(
     jintArray jmax_bytes_for_level_multiplier_additional) {
   jsize len = env->GetArrayLength(jmax_bytes_for_level_multiplier_additional);
   jint *additionals =
-      env->GetIntArrayElements(jmax_bytes_for_level_multiplier_additional, 0);
+      env->GetIntArrayElements(jmax_bytes_for_level_multiplier_additional, nullptr);
+  if(additionals == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   auto* opt = reinterpret_cast<rocksdb::Options*>(jhandle);
   opt->max_bytes_for_level_multiplier_additional.clear();
   for (jsize i = 0; i < len; i++) {
     opt->max_bytes_for_level_multiplier_additional.push_back(static_cast<int32_t>(additionals[i]));
   }
+
+  env->ReleaseIntArrayElements(jmax_bytes_for_level_multiplier_additional,
+      additionals, JNI_ABORT);
 }
 
 /*
@@ -2153,7 +2213,7 @@ void Java_org_rocksdb_Options_setParanoidFileChecks(
  */
 jlong Java_org_rocksdb_ColumnFamilyOptions_newColumnFamilyOptions(
     JNIEnv* env, jclass jcls) {
-  rocksdb::ColumnFamilyOptions* op = new rocksdb::ColumnFamilyOptions();
+  auto* op = new rocksdb::ColumnFamilyOptions();
   return reinterpret_cast<jlong>(op);
 }
 
@@ -2164,14 +2224,20 @@ jlong Java_org_rocksdb_ColumnFamilyOptions_newColumnFamilyOptions(
  */
 jlong Java_org_rocksdb_ColumnFamilyOptions_getColumnFamilyOptionsFromProps(
     JNIEnv* env, jclass jclazz, jstring jopt_string) {
-  jlong ret_value = 0;
+  const char* opt_string = env->GetStringUTFChars(jopt_string, nullptr);
-  rocksdb::ColumnFamilyOptions* cf_options =
+  if(opt_string == nullptr) {
-      new rocksdb::ColumnFamilyOptions();
+    // exception thrown: OutOfMemoryError
-  const char* opt_string = env->GetStringUTFChars(jopt_string, 0);
+    return 0;
+  }
+
+  auto* cf_options = new rocksdb::ColumnFamilyOptions();
   rocksdb::Status status = rocksdb::GetColumnFamilyOptionsFromString(
       rocksdb::ColumnFamilyOptions(), opt_string, cf_options);
+
   env->ReleaseStringUTFChars(jopt_string, opt_string);
+
   // Check if ColumnFamilyOptions creation was possible.
+  jlong ret_value = 0;
   if (status.ok()) {
     ret_value = reinterpret_cast<jlong>(cf_options);
   } else {
@@ -2189,7 +2255,9 @@ jlong Java_org_rocksdb_ColumnFamilyOptions_getColumnFamilyOptionsFromProps(
  */
 void Java_org_rocksdb_ColumnFamilyOptions_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::ColumnFamilyOptions*>(handle);
+  auto* cfo = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(handle);
+  assert(cfo != nullptr);
+  delete cfo;
 }
 
 /*
@@ -2265,10 +2333,15 @@ void Java_org_rocksdb_ColumnFamilyOptions_setComparatorHandle__JJ(
  */
 void Java_org_rocksdb_ColumnFamilyOptions_setMergeOperatorName(
     JNIEnv* env, jobject jobj, jlong jhandle, jstring jop_name) {
-  auto options = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
+  auto* options = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
-  const char* op_name = env->GetStringUTFChars(jop_name, 0);
+  const char* op_name = env->GetStringUTFChars(jop_name, nullptr);
-  options->merge_operator = rocksdb::MergeOperators::CreateFromStringId(
+  if(op_name == nullptr) {
-        op_name);
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
+  options->merge_operator =
+      rocksdb::MergeOperators::CreateFromStringId(op_name);
   env->ReleaseStringUTFChars(jop_name, op_name);
 }
 
@@ -2364,7 +2437,7 @@ void Java_org_rocksdb_ColumnFamilyOptions_setMemTableFactory(
  */
 jstring Java_org_rocksdb_ColumnFamilyOptions_memTableFactoryName(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto opt = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
+  auto* opt = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
   rocksdb::MemTableRepFactory* tf = opt->memtable_factory.get();
 
   // Should never be nullptr.
@@ -2418,7 +2491,7 @@ void Java_org_rocksdb_ColumnFamilyOptions_setTableFactory(
  */
 jstring Java_org_rocksdb_ColumnFamilyOptions_tableFactoryName(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto opt = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
+  auto* opt = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
   rocksdb::TableFactory* tf = opt->table_factory.get();
 
   // Should never be nullptr.
@@ -2508,9 +2581,13 @@ void Java_org_rocksdb_ColumnFamilyOptions_setCompressionPerLevel(
     JNIEnv* env, jobject jobj, jlong jhandle,
     jbyteArray jcompressionLevels) {
   auto* options = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
-  std::vector<rocksdb::CompressionType> compressionLevels =
+  auto uptr_compression_levels =
       rocksdb_compression_vector_helper(env, jcompressionLevels);
-  options->compression_per_level = compressionLevels;
+  if(!uptr_compression_levels) {
+      // exception occurred
+      return;
+  }
+  options->compression_per_level = *(uptr_compression_levels.get());
 }
 
 /*
@@ -2520,9 +2597,9 @@ void Java_org_rocksdb_ColumnFamilyOptions_setCompressionPerLevel(
  */
 jbyteArray Java_org_rocksdb_ColumnFamilyOptions_compressionPerLevel(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  auto* options = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
+  auto* cf_options = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
   return rocksdb_compression_list_helper(env,
-      options->compression_per_level);
+      cf_options->compression_per_level);
 }
 
 /*
@@ -2668,7 +2745,7 @@ void Java_org_rocksdb_ColumnFamilyOptions_setLevelZeroStopWritesTrigger(
  */
 jint Java_org_rocksdb_ColumnFamilyOptions_maxMemCompactionLevel(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  return 0;
+  return 0; // deprecated and intentionally not implemented, see the Java code
 }
 
 /*
@@ -2677,7 +2754,9 @@ jint Java_org_rocksdb_ColumnFamilyOptions_maxMemCompactionLevel(
  * Signature: (JI)V
  */
 void Java_org_rocksdb_ColumnFamilyOptions_setMaxMemCompactionLevel(
-    JNIEnv* env, jobject jobj, jlong jhandle, jint jmax_mem_compaction_level) {}
+    JNIEnv* env, jobject jobj, jlong jhandle, jint jmax_mem_compaction_level) {
+  // deprecated and intentionally not implemented, see the Java code
+}
 
 /*
  * Class:     org_rocksdb_ColumnFamilyOptions
@@ -3308,9 +3387,19 @@ jintArray Java_org_rocksdb_ColumnFamilyOptions_maxBytesForLevelMultiplierAdditio
   }
 
   jsize jlen = static_cast<jsize>(size);
-  jintArray result;
+  jintArray result = env->NewIntArray(jlen);
-  result = env->NewIntArray(jlen);
+  if(result == nullptr) {
+    // exception thrown: OutOfMemoryError
+    delete [] additionals;
+    return nullptr;
+  }
   env->SetIntArrayRegion(result, 0, jlen, additionals);
+  if(env->ExceptionCheck()) {
+      // exception thrown: ArrayIndexOutOfBoundsException
+      env->DeleteLocalRef(result);
+      delete [] additionals;
+      return nullptr;
+  }
 
   delete [] additionals;
 
@@ -3328,11 +3417,19 @@ void Java_org_rocksdb_ColumnFamilyOptions_setMaxBytesForLevelMultiplierAdditiona
   jsize len = env->GetArrayLength(jmax_bytes_for_level_multiplier_additional);
   jint *additionals =
       env->GetIntArrayElements(jmax_bytes_for_level_multiplier_additional, 0);
+  if(additionals == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   auto* cf_opt = reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jhandle);
   cf_opt->max_bytes_for_level_multiplier_additional.clear();
   for (jsize i = 0; i < len; i++) {
     cf_opt->max_bytes_for_level_multiplier_additional.push_back(static_cast<int32_t>(additionals[i]));
   }
+
+  env->ReleaseIntArrayElements(jmax_bytes_for_level_multiplier_additional,
+      additionals, JNI_ABORT);
 }
 
 /*
@@ -3369,7 +3466,7 @@ void Java_org_rocksdb_ColumnFamilyOptions_setParanoidFileChecks(
  */
 jlong Java_org_rocksdb_DBOptions_newDBOptions(JNIEnv* env,
     jclass jcls) {
-  rocksdb::DBOptions* dbop = new rocksdb::DBOptions();
+  auto* dbop = new rocksdb::DBOptions();
   return reinterpret_cast<jlong>(dbop);
 }
 
@@ -3380,14 +3477,20 @@ jlong Java_org_rocksdb_DBOptions_newDBOptions(JNIEnv* env,
  */
 jlong Java_org_rocksdb_DBOptions_getDBOptionsFromProps(
     JNIEnv* env, jclass jclazz, jstring jopt_string) {
-  jlong ret_value = 0;
+  const char* opt_string = env->GetStringUTFChars(jopt_string, nullptr);
-  rocksdb::DBOptions* db_options =
+  if(opt_string == nullptr) {
-      new rocksdb::DBOptions();
+    // exception thrown: OutOfMemoryError
-  const char* opt_string = env->GetStringUTFChars(jopt_string, 0);
+    return 0;
+  }
+
+  auto* db_options = new rocksdb::DBOptions();
   rocksdb::Status status = rocksdb::GetDBOptionsFromString(
       rocksdb::DBOptions(), opt_string, db_options);
+
   env->ReleaseStringUTFChars(jopt_string, opt_string);
+
   // Check if DBOptions creation was possible.
+  jlong ret_value = 0;
   if (status.ok()) {
     ret_value = reinterpret_cast<jlong>(db_options);
   } else {
@@ -3405,7 +3508,9 @@ jlong Java_org_rocksdb_DBOptions_getDBOptionsFromProps(
  */
 void Java_org_rocksdb_DBOptions_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::DBOptions*>(handle);
+  auto* dbo = reinterpret_cast<rocksdb::DBOptions*>(handle);
+  assert(dbo != nullptr);
+  delete dbo;
 }
 
 /*
@@ -3505,17 +3610,6 @@ jboolean Java_org_rocksdb_DBOptions_paranoidChecks(
   return reinterpret_cast<rocksdb::DBOptions*>(jhandle)->paranoid_checks;
 }
 
-/*
- * Class:     org_rocksdb_DBOptions
- * Method:    setOldRateLimiter
- * Signature: (JJ)V
- */
-void Java_org_rocksdb_DBOptions_setOldRateLimiter(
-    JNIEnv* env, jobject jobj, jlong jhandle, jlong jrate_limiter_handle) {
-  reinterpret_cast<rocksdb::DBOptions*>(jhandle)->rate_limiter.reset(
-      reinterpret_cast<rocksdb::RateLimiter*>(jrate_limiter_handle));
-}
-
 /*
  * Class:     org_rocksdb_DBOptions
  * Method:    setRateLimiter
@@ -3626,7 +3720,7 @@ void Java_org_rocksdb_DBOptions_createStatistics(
  */
 jlong Java_org_rocksdb_DBOptions_statisticsPtr(
     JNIEnv* env, jobject jobj, jlong jOptHandle) {
-  auto st = reinterpret_cast<rocksdb::DBOptions*>(jOptHandle)->
+  auto* st = reinterpret_cast<rocksdb::DBOptions*>(jOptHandle)->
       statistics.get();
   return reinterpret_cast<jlong>(st);
 }
@@ -3659,7 +3753,12 @@ jboolean Java_org_rocksdb_DBOptions_useFsync(
  */
 void Java_org_rocksdb_DBOptions_setDbLogDir(
     JNIEnv* env, jobject jobj, jlong jhandle, jstring jdb_log_dir) {
-  const char* log_dir = env->GetStringUTFChars(jdb_log_dir, 0);
+  const char* log_dir = env->GetStringUTFChars(jdb_log_dir, nullptr);
+  if(log_dir == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   reinterpret_cast<rocksdb::DBOptions*>(jhandle)->db_log_dir.assign(log_dir);
   env->ReleaseStringUTFChars(jdb_log_dir, log_dir);
 }
@@ -4307,19 +4406,17 @@ jlong Java_org_rocksdb_DBOptions_writeThreadSlowYieldUsec(
 }
 
 void Java_org_rocksdb_DBOptions_setDelayedWriteRate(
-  JNIEnv* env, jobject jobj, jlong jhandle, jlong delay_write_rate){
+    JNIEnv* env, jobject jobj, jlong jhandle, jlong delay_write_rate) {
-
+  reinterpret_cast<rocksdb::DBOptions*>(jhandle)->delayed_write_rate =
-    reinterpret_cast<rocksdb::DBOptions*>(jhandle)->
+      static_cast<int64_t>(delay_write_rate);
-        delayed_write_rate = static_cast<int64_t>(delay_write_rate);
+}
-
-  }
 
-  jlong Java_org_rocksdb_DBOptions_delayedWriteRate(
+jlong Java_org_rocksdb_DBOptions_delayedWriteRate(
-    JNIEnv* env, jobject jobj, jlong jhandle){
+    JNIEnv* env, jobject jobj, jlong jhandle) {
+  return reinterpret_cast<rocksdb::DBOptions*>(jhandle)->
+      delayed_write_rate;
+}
 
-      return reinterpret_cast<rocksdb::DBOptions*>(jhandle)->
-          delayed_write_rate;
-    }
 //////////////////////////////////////////////////////////////////////////////
 // rocksdb::WriteOptions
 
@@ -4330,7 +4427,7 @@ void Java_org_rocksdb_DBOptions_setDelayedWriteRate(
  */
 jlong Java_org_rocksdb_WriteOptions_newWriteOptions(
     JNIEnv* env, jclass jcls) {
-  rocksdb::WriteOptions* op = new rocksdb::WriteOptions();
+  auto* op = new rocksdb::WriteOptions();
   return reinterpret_cast<jlong>(op);
 }
 
@@ -4341,7 +4438,8 @@ jlong Java_org_rocksdb_WriteOptions_newWriteOptions(
  */
 void Java_org_rocksdb_WriteOptions_disposeInternal(
     JNIEnv* env, jobject jwrite_options, jlong jhandle) {
-  auto write_options = reinterpret_cast<rocksdb::WriteOptions*>(jhandle);
+  auto* write_options = reinterpret_cast<rocksdb::WriteOptions*>(jhandle);
+  assert(write_options != nullptr);
   delete write_options;
 }
 
@@ -4395,8 +4493,8 @@ jboolean Java_org_rocksdb_WriteOptions_disableWAL(
  */
 jlong Java_org_rocksdb_ReadOptions_newReadOptions(
     JNIEnv* env, jclass jcls) {
-  auto read_opt = new rocksdb::ReadOptions();
+  auto* read_options = new rocksdb::ReadOptions();
-  return reinterpret_cast<jlong>(read_opt);
+  return reinterpret_cast<jlong>(read_options);
 }
 
 /*
@@ -4406,7 +4504,9 @@ jlong Java_org_rocksdb_ReadOptions_newReadOptions(
  */
 void Java_org_rocksdb_ReadOptions_disposeInternal(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  delete reinterpret_cast<rocksdb::ReadOptions*>(jhandle);
+  auto* read_options = reinterpret_cast<rocksdb::ReadOptions*>(jhandle);
+  assert(read_options != nullptr);
+  delete read_options;
 }
 
 /*
@@ -4613,7 +4713,7 @@ void Java_org_rocksdb_ReadOptions_setReadTier(
  */
 jlong Java_org_rocksdb_ComparatorOptions_newComparatorOptions(
     JNIEnv* env, jclass jcls) {
-  auto comparator_opt = new rocksdb::ComparatorJniCallbackOptions();
+  auto* comparator_opt = new rocksdb::ComparatorJniCallbackOptions();
   return reinterpret_cast<jlong>(comparator_opt);
 }
 
@@ -4646,7 +4746,10 @@ void Java_org_rocksdb_ComparatorOptions_setUseAdaptiveMutex(
  */
 void Java_org_rocksdb_ComparatorOptions_disposeInternal(
     JNIEnv * env, jobject jobj, jlong jhandle) {
-  delete reinterpret_cast<rocksdb::ComparatorJniCallbackOptions*>(jhandle);
+  auto* comparator_opt =
+      reinterpret_cast<rocksdb::ComparatorJniCallbackOptions*>(jhandle);
+  assert(comparator_opt != nullptr);
+  delete comparator_opt;
 }
 
 /////////////////////////////////////////////////////////////////////
@@ -4659,7 +4762,7 @@ void Java_org_rocksdb_ComparatorOptions_disposeInternal(
  */
 jlong Java_org_rocksdb_FlushOptions_newFlushOptions(
     JNIEnv* env, jclass jcls) {
-  auto flush_opt = new rocksdb::FlushOptions();
+  auto* flush_opt = new rocksdb::FlushOptions();
   return reinterpret_cast<jlong>(flush_opt);
 }
 
@@ -4692,5 +4795,7 @@ jboolean Java_org_rocksdb_FlushOptions_waitForFlush(
  */
 void Java_org_rocksdb_FlushOptions_disposeInternal(
     JNIEnv * env, jobject jobj, jlong jhandle) {
-  delete reinterpret_cast<rocksdb::FlushOptions*>(jhandle);
+  auto* flush_opt = reinterpret_cast<rocksdb::FlushOptions*>(jhandle);
+  assert(flush_opt != nullptr);
+  delete flush_opt;
 }

java/rocksjni/ratelimiterjni.cc

@@ -6,24 +6,9 @@
 // This file implements the "bridge" between Java and C++ for RateLimiter.
 
 #include "rocksjni/portal.h"
-#include "include/org_rocksdb_GenericRateLimiterConfig.h"
 #include "include/org_rocksdb_RateLimiter.h"
 #include "rocksdb/rate_limiter.h"
 
-/*
- * Class:     org_rocksdb_GenericRateLimiterConfig
- * Method:    newRateLimiterHandle
- * Signature: (JJI)J
- */
-jlong Java_org_rocksdb_GenericRateLimiterConfig_newRateLimiterHandle(
-    JNIEnv* env, jobject jobj, jlong jrate_bytes_per_second,
-    jlong jrefill_period_micros, jint jfairness) {
-  return reinterpret_cast<jlong>(rocksdb::NewGenericRateLimiter(
-      static_cast<int64_t>(jrate_bytes_per_second),
-      static_cast<int64_t>(jrefill_period_micros),
-      static_cast<int32_t>(jfairness)));
-}
-
 /*
  * Class:     org_rocksdb_RateLimiter
  * Method:    newRateLimiterHandle
@@ -32,16 +17,13 @@ jlong Java_org_rocksdb_GenericRateLimiterConfig_newRateLimiterHandle(
 jlong Java_org_rocksdb_RateLimiter_newRateLimiterHandle(
     JNIEnv* env, jclass jclazz, jlong jrate_bytes_per_second,
     jlong jrefill_period_micros, jint jfairness) {
-  auto* rate_limiter = rocksdb::NewGenericRateLimiter(
+  auto * sptr_rate_limiter =
-      static_cast<int64_t>(jrate_bytes_per_second),
+      new std::shared_ptr<rocksdb::RateLimiter>(rocksdb::NewGenericRateLimiter(
-      static_cast<int64_t>(jrefill_period_micros),
+          static_cast<int64_t>(jrate_bytes_per_second),
-      static_cast<int32_t>(jfairness));
+          static_cast<int64_t>(jrefill_period_micros),
+          static_cast<int32_t>(jfairness)));
 
-  std::shared_ptr<rocksdb::RateLimiter> *ptr_sptr_rate_limiter =
+  return reinterpret_cast<jlong>(sptr_rate_limiter);
-    new std::shared_ptr<rocksdb::RateLimiter>;
-  *ptr_sptr_rate_limiter = std::shared_ptr<rocksdb::RateLimiter>(rate_limiter);
-
-  return reinterpret_cast<jlong>(ptr_sptr_rate_limiter);
 }
 
 /*
@@ -51,10 +33,9 @@ jlong Java_org_rocksdb_RateLimiter_newRateLimiterHandle(
  */
 void Java_org_rocksdb_RateLimiter_disposeInternal(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  std::shared_ptr<rocksdb::RateLimiter> *handle =
+  auto* handle =
       reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(jhandle);
-  handle->reset();
+  delete handle;  // delete std::shared_ptr
-  delete handle;
 }
 
 /*
@@ -65,8 +46,8 @@ void Java_org_rocksdb_RateLimiter_disposeInternal(
 void Java_org_rocksdb_RateLimiter_setBytesPerSecond(
     JNIEnv* env, jobject jobj, jlong handle,
     jlong jbytes_per_second) {
-  reinterpret_cast<rocksdb::RateLimiter*>(
+  reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(handle)->get()->
-      handle)->SetBytesPerSecond(jbytes_per_second);
+      SetBytesPerSecond(jbytes_per_second);
 }
 
 /*
@@ -77,9 +58,8 @@ void Java_org_rocksdb_RateLimiter_setBytesPerSecond(
 void Java_org_rocksdb_RateLimiter_request(
     JNIEnv* env, jobject jobj, jlong handle,
     jlong jbytes) {
-  reinterpret_cast<rocksdb::RateLimiter*>(
+  reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(handle)->get()->
-      handle)->Request(jbytes,
+      Request(jbytes, rocksdb::Env::IO_TOTAL);
-      rocksdb::Env::IO_TOTAL);
 }
 
 /*
@@ -88,10 +68,9 @@ void Java_org_rocksdb_RateLimiter_request(
  * Signature: (J)J
  */
 jlong Java_org_rocksdb_RateLimiter_getSingleBurstBytes(
-    JNIEnv* env, jobject jobj, jlong handle,
+    JNIEnv* env, jobject jobj, jlong handle) {
-    jlong jbytes) {
+  return reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(handle)->
-  return reinterpret_cast<rocksdb::RateLimiter*>(
+      get()->GetSingleBurstBytes();
-      handle)->GetSingleBurstBytes();
 }
 
 /*
@@ -100,10 +79,9 @@ jlong Java_org_rocksdb_RateLimiter_getSingleBurstBytes(
  * Signature: (J)J
  */
 jlong Java_org_rocksdb_RateLimiter_getTotalBytesThrough(
-    JNIEnv* env, jobject jobj, jlong handle,
+    JNIEnv* env, jobject jobj, jlong handle) {
-    jlong jbytes) {
+  return reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(handle)->
-  return reinterpret_cast<rocksdb::RateLimiter*>(
+      get()->GetTotalBytesThrough();
-      handle)->GetTotalBytesThrough();
 }
 
 /*
@@ -112,8 +90,7 @@ jlong Java_org_rocksdb_RateLimiter_getTotalBytesThrough(
  * Signature: (J)J
  */
 jlong Java_org_rocksdb_RateLimiter_getTotalRequests(
-    JNIEnv* env, jobject jobj, jlong handle,
+    JNIEnv* env, jobject jobj, jlong handle) {
-    jlong jbytes) {
+  return reinterpret_cast<std::shared_ptr<rocksdb::RateLimiter> *>(handle)->
-  return reinterpret_cast<rocksdb::RateLimiter*>(
+      get()->GetTotalRequests();
-      handle)->GetTotalRequests();
 }

java/rocksjni/restorejni.cc

@@ -22,7 +22,7 @@
  */
 jlong Java_org_rocksdb_RestoreOptions_newRestoreOptions(JNIEnv* env,
     jclass jcls, jboolean keep_log_files) {
-  auto ropt = new rocksdb::RestoreOptions(keep_log_files);
+  auto* ropt = new rocksdb::RestoreOptions(keep_log_files);
   return reinterpret_cast<jlong>(ropt);
 }
 
@@ -33,7 +33,7 @@ jlong Java_org_rocksdb_RestoreOptions_newRestoreOptions(JNIEnv* env,
  */
 void Java_org_rocksdb_RestoreOptions_disposeInternal(JNIEnv* env, jobject jobj,
     jlong jhandle) {
-  auto ropt = reinterpret_cast<rocksdb::RestoreOptions*>(jhandle);
+  auto* ropt = reinterpret_cast<rocksdb::RestoreOptions*>(jhandle);
   assert(ropt);
   delete ropt;
 }

java/rocksjni/slice.cc

@@ -26,8 +26,17 @@
  */
 jlong Java_org_rocksdb_AbstractSlice_createNewSliceFromString(
     JNIEnv * env, jclass jcls, jstring jstr) {
-  const auto* str = env->GetStringUTFChars(jstr, NULL);
+  const auto* str = env->GetStringUTFChars(jstr, nullptr);
+  if(str == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return 0;
+  }
+
   const size_t len = strlen(str);
+
+  // NOTE: buf will be deleted in the
+  // Java_org_rocksdb_Slice_disposeInternalBuf or
+  // or Java_org_rocksdb_DirectSlice_disposeInternalBuf methods
   char* buf = new char[len + 1];
   memcpy(buf, str, len);
   buf[len] = 0;
@@ -118,13 +127,18 @@ void Java_org_rocksdb_AbstractSlice_disposeInternal(
  */
 jlong Java_org_rocksdb_Slice_createNewSlice0(
     JNIEnv * env, jclass jcls, jbyteArray data, jint offset) {
-
   const jsize dataSize = env->GetArrayLength(data);
   const int len = dataSize - offset;
-  jbyte* ptrData = new jbyte[len];
-  env->GetByteArrayRegion(data, offset, len, ptrData);
 
-  const auto* slice = new rocksdb::Slice((const char*)ptrData, len);
+  // NOTE: buf will be deleted in the Java_org_rocksdb_Slice_disposeInternalBuf method
+  jbyte* buf = new jbyte[len];
+  env->GetByteArrayRegion(data, offset, len, buf);
+  if(env->ExceptionCheck()) {
+    // exception thrown: ArrayIndexOutOfBoundsException
+    return 0;
+  }
+
+  const auto* slice = new rocksdb::Slice((const char*)buf, len);
   return reinterpret_cast<jlong>(slice);
 }
 
@@ -135,16 +149,17 @@ jlong Java_org_rocksdb_Slice_createNewSlice0(
  */
 jlong Java_org_rocksdb_Slice_createNewSlice1(
     JNIEnv * env, jclass jcls, jbyteArray data) {
-
+  jbyte* ptrData = env->GetByteArrayElements(data, nullptr);
+  if(ptrData == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return 0;
+  }
   const int len = env->GetArrayLength(data) + 1;
 
-  jboolean isCopy;
+  // NOTE: buf will be deleted in the Java_org_rocksdb_Slice_disposeInternalBuf method
-  jbyte* ptrData = env->GetByteArrayElements(data, &isCopy);
-
-  // NOTE: buf will be deleted in the org.rocksdb.Slice#dispose method
   char* buf = new char[len];
   memcpy(buf, ptrData, len - 1);
-  buf[len-1]='\0';
+  buf[len-1] = '\0';
 
   const auto* slice =
       new rocksdb::Slice(buf, len - 1);
@@ -162,22 +177,61 @@ jlong Java_org_rocksdb_Slice_createNewSlice1(
 jbyteArray Java_org_rocksdb_Slice_data0(
     JNIEnv* env, jobject jobj, jlong handle) {
   const auto* slice = reinterpret_cast<rocksdb::Slice*>(handle);
-  const int len = static_cast<int>(slice->size());
+  const jsize len = static_cast<jsize>(slice->size());
   const jbyteArray data = env->NewByteArray(len);
+  if(data == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return nullptr;
+  }
+  
   env->SetByteArrayRegion(data, 0, len,
     reinterpret_cast<const jbyte*>(slice->data()));
+  if(env->ExceptionCheck()) {
+    // exception thrown: ArrayIndexOutOfBoundsException
+    env->DeleteLocalRef(data);
+    return nullptr;
+  }
+
   return data;
 }
 
+/*
+ * Class:     org_rocksdb_Slice
+ * Method:    clear0
+ * Signature: (JZJ)V
+ */
+void Java_org_rocksdb_Slice_clear0(
+    JNIEnv * env, jobject jobj, jlong handle, jboolean shouldRelease,
+    jlong internalBufferOffset) {
+  auto* slice = reinterpret_cast<rocksdb::Slice*>(handle);
+  if(shouldRelease == JNI_TRUE) {
+    const char* buf = slice->data_ - internalBufferOffset;
+    delete [] buf;
+  }
+  slice->clear();
+}
+
+/*
+ * Class:     org_rocksdb_Slice
+ * Method:    removePrefix0
+ * Signature: (JI)V
+ */
+void Java_org_rocksdb_Slice_removePrefix0(
+    JNIEnv * env, jobject jobj, jlong handle, jint length) {
+  auto* slice = reinterpret_cast<rocksdb::Slice*>(handle);
+  slice->remove_prefix(length);
+}
+
 /*
  * Class:     org_rocksdb_Slice
  * Method:    disposeInternalBuf
- * Signature: (J)V
+ * Signature: (JJ)V
  */
 void Java_org_rocksdb_Slice_disposeInternalBuf(
-    JNIEnv * env, jobject jobj, jlong handle) {
+    JNIEnv * env, jobject jobj, jlong handle, jlong internalBufferOffset) {
   const auto* slice = reinterpret_cast<rocksdb::Slice*>(handle);
-  delete [] slice->data_;
+  const char* buf = slice->data_ - internalBufferOffset;
+  delete [] buf;
 }
 
 // </editor-fold>
@@ -191,8 +245,19 @@ void Java_org_rocksdb_Slice_disposeInternalBuf(
  */
 jlong Java_org_rocksdb_DirectSlice_createNewDirectSlice0(
     JNIEnv* env, jclass jcls, jobject data, jint length) {
+  assert(data != nullptr);
+  void* data_addr = env->GetDirectBufferAddress(data);
+  if(data_addr == nullptr) {
+    // error: memory region is undefined, given object is not a direct
+    // java.nio.Buffer, or JNI access to direct buffers is not supported by JVM
+    rocksdb::IllegalArgumentExceptionJni::ThrowNew(env,
+        rocksdb::Status::InvalidArgument(
+            "Could not access DirectBuffer"));
+    return 0;
+  }
+
   const auto* ptrData =
-     reinterpret_cast<char*>(env->GetDirectBufferAddress(data));
+     reinterpret_cast<char*>(data_addr);
   const auto* slice = new rocksdb::Slice(ptrData, length);
   return reinterpret_cast<jlong>(slice);
 }
@@ -204,8 +269,17 @@ jlong Java_org_rocksdb_DirectSlice_createNewDirectSlice0(
  */
 jlong Java_org_rocksdb_DirectSlice_createNewDirectSlice1(
     JNIEnv* env, jclass jcls, jobject data) {
-  const auto* ptrData =
+  void* data_addr = env->GetDirectBufferAddress(data);
-    reinterpret_cast<char*>(env->GetDirectBufferAddress(data));
+  if(data_addr == nullptr) {
+    // error: memory region is undefined, given object is not a direct
+    // java.nio.Buffer, or JNI access to direct buffers is not supported by JVM
+    rocksdb::IllegalArgumentExceptionJni::ThrowNew(env,
+        rocksdb::Status::InvalidArgument(
+            "Could not access DirectBuffer"));
+    return 0;
+  }
+
+  const auto* ptrData = reinterpret_cast<char*>(data_addr);
   const auto* slice = new rocksdb::Slice(ptrData);
   return reinterpret_cast<jlong>(slice);
 }
@@ -236,12 +310,16 @@ jbyte Java_org_rocksdb_DirectSlice_get0(
 /*
  * Class:     org_rocksdb_DirectSlice
  * Method:    clear0
- * Signature: (J)V
+ * Signature: (JZJ)V
  */
 void Java_org_rocksdb_DirectSlice_clear0(
-    JNIEnv* env, jobject jobj, jlong handle) {
+    JNIEnv* env, jobject jobj, jlong handle,
+    jboolean shouldRelease, jlong internalBufferOffset) {
   auto* slice = reinterpret_cast<rocksdb::Slice*>(handle);
-  delete [] slice->data_;
+  if(shouldRelease == JNI_TRUE) {
+    const char* buf = slice->data_ - internalBufferOffset;
+    delete [] buf;
+  }
   slice->clear();
 }
 
@@ -256,4 +334,16 @@ void Java_org_rocksdb_DirectSlice_removePrefix0(
   slice->remove_prefix(length);
 }
 
+/*
+ * Class:     org_rocksdb_DirectSlice
+ * Method:    disposeInternalBuf
+ * Signature: (JJ)V
+ */
+void Java_org_rocksdb_DirectSlice_disposeInternalBuf(
+    JNIEnv* env, jobject jobj, jlong handle, jlong internalBufferOffset) {
+  const auto* slice = reinterpret_cast<rocksdb::Slice*>(handle);
+  const char* buf = slice->data_ - internalBufferOffset;
+  delete [] buf;
+}
+
 // </editor-fold>

java/rocksjni/sst_file_writerjni.cc

@@ -42,7 +42,11 @@ jlong Java_org_rocksdb_SstFileWriter_newSstFileWriter(JNIEnv *env, jclass jcls,
  */
 void Java_org_rocksdb_SstFileWriter_open(JNIEnv *env, jobject jobj,
                                          jlong jhandle, jstring jfile_path) {
-  const char *file_path = env->GetStringUTFChars(jfile_path, NULL);
+  const char *file_path = env->GetStringUTFChars(jfile_path, nullptr);
+  if(file_path == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
   rocksdb::Status s =
       reinterpret_cast<rocksdb::SstFileWriter *>(jhandle)->Open(file_path);
   env->ReleaseStringUTFChars(jfile_path, file_path);
@@ -62,8 +66,9 @@ void Java_org_rocksdb_SstFileWriter_add(JNIEnv *env, jobject jobj,
                                         jlong jvalue_handle) {
   auto *key_slice = reinterpret_cast<rocksdb::Slice *>(jkey_handle);
   auto *value_slice = reinterpret_cast<rocksdb::Slice *>(jvalue_handle);
-  rocksdb::Status s = reinterpret_cast<rocksdb::SstFileWriter *>(jhandle)->Add(
+  rocksdb::Status s =
-      *key_slice, *value_slice);
+      reinterpret_cast<rocksdb::SstFileWriter *>(jhandle)->Add(*key_slice,
+          *value_slice);
   if (!s.ok()) {
     rocksdb::RocksDBExceptionJni::ThrowNew(env, s);
   }

java/rocksjni/statistics.cc

@@ -21,9 +21,8 @@
  */
 jlong Java_org_rocksdb_Statistics_getTickerCount0(
     JNIEnv* env, jobject jobj, jint tickerType, jlong handle) {
-  auto st = reinterpret_cast<rocksdb::Statistics*>(handle);
+  auto* st = reinterpret_cast<rocksdb::Statistics*>(handle);
   assert(st != nullptr);
-
   return st->getTickerCount(static_cast<rocksdb::Tickers>(tickerType));
 }
 
@@ -34,17 +33,28 @@ jlong Java_org_rocksdb_Statistics_getTickerCount0(
  */
 jobject Java_org_rocksdb_Statistics_getHistogramData0(
     JNIEnv* env, jobject jobj, jint histogramType, jlong handle) {
-  auto st = reinterpret_cast<rocksdb::Statistics*>(handle);
+  auto* st = reinterpret_cast<rocksdb::Statistics*>(handle);
   assert(st != nullptr);
 
   rocksdb::HistogramData data;
   st->histogramData(static_cast<rocksdb::Histograms>(histogramType),
     &data);
 
-  // Don't reuse class pointer
+  jclass jclazz = rocksdb::HistogramDataJni::getJClass(env);
-  jclass jclazz = env->FindClass("org/rocksdb/HistogramData");
+  if(jclazz == nullptr) {
+    // exception occurred accessing class
+    return nullptr;
+  }
+
   jmethodID mid = rocksdb::HistogramDataJni::getConstructorMethodId(
-      env, jclazz);
+      env);
-  return env->NewObject(jclazz, mid, data.median, data.percentile95,
+  if(mid == nullptr) {
-      data.percentile99, data.average, data.standard_deviation);
+    // exception occurred accessing method
+    return nullptr;
+  }
+
+  return env->NewObject(
+      jclazz,
+      mid, data.median, data.percentile95,data.percentile99, data.average,
+      data.standard_deviation);
 }

java/rocksjni/transaction_log.cc

@@ -67,12 +67,5 @@ jobject Java_org_rocksdb_TransactionLogIterator_getBatch(
     JNIEnv* env, jobject jobj, jlong handle) {
   rocksdb::BatchResult batch_result =
       reinterpret_cast<rocksdb::TransactionLogIterator*>(handle)->GetBatch();
-  jclass jclazz = env->FindClass(
+  return rocksdb::BatchResultJni::construct(env, batch_result);
-      "org/rocksdb/TransactionLogIterator$BatchResult");
-  assert(jclazz != nullptr);
-  jmethodID mid = env->GetMethodID(
-      jclazz, "<init>", "(Lorg/rocksdb/TransactionLogIterator;JJ)V");
-  assert(mid != nullptr);
-  return env->NewObject(jclazz, mid, jobj,
-      batch_result.sequence, batch_result.writeBatchPtr.release());
 }

java/rocksjni/ttl.cc

@@ -26,9 +26,14 @@
 jlong Java_org_rocksdb_TtlDB_open(JNIEnv* env,
     jclass jcls, jlong joptions_handle, jstring jdb_path,
     jint jttl, jboolean jread_only) {
+  const char* db_path = env->GetStringUTFChars(jdb_path, nullptr);
+  if(db_path == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return 0;
+  }
+
   auto* opt = reinterpret_cast<rocksdb::Options*>(joptions_handle);
   rocksdb::DBWithTTL* db = nullptr;
-  const char* db_path = env->GetStringUTFChars(jdb_path, 0);
   rocksdb::Status s = rocksdb::DBWithTTL::Open(*opt, db_path, &db,
       jttl, jread_only);
   env->ReleaseStringUTFChars(jdb_path, db_path);
@@ -53,49 +58,69 @@ jlongArray
     JNIEnv* env, jclass jcls, jlong jopt_handle, jstring jdb_path,
     jobjectArray jcolumn_names, jlongArray jcolumn_options,
     jintArray jttls, jboolean jread_only) {
-  auto* opt = reinterpret_cast<rocksdb::DBOptions*>(jopt_handle);
+  const char* db_path = env->GetStringUTFChars(jdb_path, nullptr);
-  const char* db_path = env->GetStringUTFChars(jdb_path, NULL);
+  if(db_path == nullptr) {
-
+    // exception thrown: OutOfMemoryError
-  std::vector<rocksdb::ColumnFamilyDescriptor> column_families;
+    return 0;
-
+  }
-  jsize len_cols = env->GetArrayLength(jcolumn_names);
-  jlong* jco = env->GetLongArrayElements(jcolumn_options, NULL);
-  for(int i = 0; i < len_cols; i++) {
-    jobject jcn = env->GetObjectArrayElement(jcolumn_names, i);
-    jbyteArray jcn_ba = reinterpret_cast<jbyteArray>(jcn);
-    jbyte* jcf_name = env->GetByteArrayElements(jcn_ba, NULL);
-    const int jcf_name_len = env->GetArrayLength(jcn_ba);
 
-    //TODO(AR) do I need to make a copy of jco[i] ?
+  const jsize len_cols = env->GetArrayLength(jcolumn_names);
+  jlong* jco = env->GetLongArrayElements(jcolumn_options, nullptr);
+  if(jco == nullptr) {
+    // exception thrown: OutOfMemoryError
+    env->ReleaseStringUTFChars(jdb_path, db_path);
+    return nullptr;
+  }
 
-    std::string cf_name (reinterpret_cast<char *>(jcf_name), jcf_name_len);
+  std::vector<rocksdb::ColumnFamilyDescriptor> column_families;
-    rocksdb::ColumnFamilyOptions* cf_options =
+  jboolean has_exception = JNI_FALSE;
-      reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jco[i]);
+  rocksdb::JniUtil::byteStrings<std::string>(
-    column_families.push_back(
+    env,
-      rocksdb::ColumnFamilyDescriptor(cf_name, *cf_options));
+    jcolumn_names,
+    [](const char* str_data, const size_t str_len) {
+      return std::string(str_data, str_len);
+    },
+    [&jco, &column_families](size_t idx, std::string cf_name) {
+      rocksdb::ColumnFamilyOptions* cf_options =
+          reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jco[idx]);
+      column_families.push_back(
+          rocksdb::ColumnFamilyDescriptor(cf_name, *cf_options));
+    },
+    &has_exception);
 
-    env->ReleaseByteArrayElements(jcn_ba, jcf_name, JNI_ABORT);
-    env->DeleteLocalRef(jcn);
-  }
   env->ReleaseLongArrayElements(jcolumn_options, jco, JNI_ABORT);
 
-  std::vector<rocksdb::ColumnFamilyHandle*> handles;
+  if(has_exception == JNI_TRUE) {
-  rocksdb::DBWithTTL* db = nullptr;
+    // exception occured
+    env->ReleaseStringUTFChars(jdb_path, db_path);
+    return nullptr;
+  }
 
   std::vector<int32_t> ttl_values;
-  jint* jttlv = env->GetIntArrayElements(jttls, NULL);
+  jint* jttlv = env->GetIntArrayElements(jttls, nullptr);
-  jsize len_ttls = env->GetArrayLength(jttls);
+  if(jttlv == nullptr) {
-  for(int i = 0; i < len_ttls; i++) {
+    // exception thrown: OutOfMemoryError
+    env->ReleaseStringUTFChars(jdb_path, db_path);
+    return nullptr;
+  }
+  const jsize len_ttls = env->GetArrayLength(jttls);
+  for(jsize i = 0; i < len_ttls; i++) {
     ttl_values.push_back(jttlv[i]);
   }
   env->ReleaseIntArrayElements(jttls, jttlv, JNI_ABORT);
 
+  auto* opt = reinterpret_cast<rocksdb::DBOptions*>(jopt_handle);
+  std::vector<rocksdb::ColumnFamilyHandle*> handles;
+  rocksdb::DBWithTTL* db = nullptr;
   rocksdb::Status s = rocksdb::DBWithTTL::Open(*opt, db_path, column_families,
       &handles, &db, ttl_values, jread_only);
 
+  // we have now finished with db_path
+  env->ReleaseStringUTFChars(jdb_path, db_path);
+
   // check if open operation was successful
   if (s.ok()) {
-    jsize resultsLen = 1 + len_cols; //db handle + column family handles
+    const jsize resultsLen = 1 + len_cols; //db handle + column family handles
     std::unique_ptr<jlong[]> results =
         std::unique_ptr<jlong[]>(new jlong[resultsLen]);
     results[0] = reinterpret_cast<jlong>(db);
@@ -104,7 +129,18 @@ jlongArray
     }
 
     jlongArray jresults = env->NewLongArray(resultsLen);
+    if(jresults == nullptr) {
+      // exception thrown: OutOfMemoryError
+      return nullptr;
+    }
+
     env->SetLongArrayRegion(jresults, 0, resultsLen, results.get());
+    if(env->ExceptionCheck()) {
+      // exception thrown: ArrayIndexOutOfBoundsException
+      env->DeleteLocalRef(jresults);
+      return nullptr;
+    }
+
     return jresults;
   } else {
     rocksdb::RocksDBExceptionJni::ThrowNew(env, s);
@@ -120,18 +156,23 @@ jlongArray
 jlong Java_org_rocksdb_TtlDB_createColumnFamilyWithTtl(
     JNIEnv* env, jobject jobj, jlong jdb_handle,
     jbyteArray jcolumn_name, jlong jcolumn_options, jint jttl) {
-  rocksdb::ColumnFamilyHandle* handle;
-  auto* db_handle = reinterpret_cast<rocksdb::DBWithTTL*>(jdb_handle);
 
-  jbyte* cfname = env->GetByteArrayElements(jcolumn_name, 0);
+  jbyte* cfname = env->GetByteArrayElements(jcolumn_name, nullptr);
-  const int len = env->GetArrayLength(jcolumn_name);
+  if(cfname == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return 0;
+  }
+  const jsize len = env->GetArrayLength(jcolumn_name);
 
   auto* cfOptions =
       reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jcolumn_options);
 
+  auto* db_handle = reinterpret_cast<rocksdb::DBWithTTL*>(jdb_handle);
+  rocksdb::ColumnFamilyHandle* handle;
   rocksdb::Status s = db_handle->CreateColumnFamilyWithTtl(
       *cfOptions, std::string(reinterpret_cast<char *>(cfname),
           len), &handle, jttl);
+
   env->ReleaseByteArrayElements(jcolumn_name, cfname, 0);
 
   if (s.ok()) {

java/rocksjni/write_batch.cc

@@ -30,8 +30,7 @@
  */
 jlong Java_org_rocksdb_WriteBatch_newWriteBatch(
     JNIEnv* env, jclass jcls, jint jreserved_bytes) {
-  rocksdb::WriteBatch* wb = new rocksdb::WriteBatch(
+  auto* wb = new rocksdb::WriteBatch(static_cast<size_t>(jreserved_bytes));
-      static_cast<size_t>(jreserved_bytes));
   return reinterpret_cast<jlong>(wb);
 }
 
@@ -244,7 +243,9 @@ void Java_org_rocksdb_WriteBatch_iterate(
  */
 void Java_org_rocksdb_WriteBatch_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::WriteBatch*>(handle);
+  auto* wb = reinterpret_cast<rocksdb::WriteBatch*>(handle);
+  assert(wb != nullptr);
+  delete wb;
 }
 
 /*
@@ -254,9 +255,8 @@ void Java_org_rocksdb_WriteBatch_disposeInternal(
  */
 jlong Java_org_rocksdb_WriteBatch_00024Handler_createNewHandler0(
     JNIEnv* env, jobject jobj) {
-  const rocksdb::WriteBatchHandlerJniCallback* h =
+  auto* wbjnic = new rocksdb::WriteBatchHandlerJniCallback(env, jobj);
-    new rocksdb::WriteBatchHandlerJniCallback(env, jobj);
+  return reinterpret_cast<jlong>(wbjnic);
-  return reinterpret_cast<jlong>(h);
 }
 
 /*
@@ -266,5 +266,8 @@ jlong Java_org_rocksdb_WriteBatch_00024Handler_createNewHandler0(
  */
 void Java_org_rocksdb_WriteBatch_00024Handler_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  delete reinterpret_cast<rocksdb::WriteBatchHandlerJniCallback*>(handle);
+  auto* wbjnic =
+      reinterpret_cast<rocksdb::WriteBatchHandlerJniCallback*>(handle);
+  assert(wbjnic != nullptr);
+  delete wbjnic;
 }

java/rocksjni/write_batch_test.cc

@@ -101,8 +101,18 @@ jbyteArray Java_org_rocksdb_WriteBatchTest_getContents(
   delete mem->Unref();
 
   jbyteArray jstate = env->NewByteArray(static_cast<jsize>(state.size()));
+  if(jstate == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return nullptr;
+  }
+
   env->SetByteArrayRegion(jstate, 0, static_cast<jsize>(state.size()),
                           reinterpret_cast<const jbyte*>(state.c_str()));
+  if(env->ExceptionCheck()) {
+    // exception thrown: ArrayIndexOutOfBoundsException
+    env->DeleteLocalRef(jstate);
+    return nullptr;
+  }
 
   return jstate;
 }

java/rocksjni/write_batch_with_index.cc

@@ -19,7 +19,7 @@
  */
 jlong Java_org_rocksdb_WriteBatchWithIndex_newWriteBatchWithIndex__(
     JNIEnv* env, jclass jcls) {
-  rocksdb::WriteBatchWithIndex* wbwi = new rocksdb::WriteBatchWithIndex();
+  auto* wbwi = new rocksdb::WriteBatchWithIndex();
   return reinterpret_cast<jlong>(wbwi);
 }
 
@@ -30,9 +30,9 @@ jlong Java_org_rocksdb_WriteBatchWithIndex_newWriteBatchWithIndex__(
  */
 jlong Java_org_rocksdb_WriteBatchWithIndex_newWriteBatchWithIndex__Z(
     JNIEnv* env, jclass jcls, jboolean joverwrite_key) {
-  rocksdb::WriteBatchWithIndex* wbwi =
+  auto* wbwi =
       new rocksdb::WriteBatchWithIndex(rocksdb::BytewiseComparator(), 0,
-      static_cast<bool>(joverwrite_key));
+          static_cast<bool>(joverwrite_key));
   return reinterpret_cast<jlong>(wbwi);
 }
 
@@ -44,10 +44,10 @@ jlong Java_org_rocksdb_WriteBatchWithIndex_newWriteBatchWithIndex__Z(
 jlong Java_org_rocksdb_WriteBatchWithIndex_newWriteBatchWithIndex__JIZ(
     JNIEnv* env, jclass jcls, jlong jfallback_index_comparator_handle,
     jint jreserved_bytes, jboolean joverwrite_key) {
-  rocksdb::WriteBatchWithIndex* wbwi =
+  auto* wbwi =
       new rocksdb::WriteBatchWithIndex(
-      reinterpret_cast<rocksdb::Comparator*>(jfallback_index_comparator_handle),
+          reinterpret_cast<rocksdb::Comparator*>(jfallback_index_comparator_handle),
-      static_cast<size_t>(jreserved_bytes), static_cast<bool>(joverwrite_key));
+          static_cast<size_t>(jreserved_bytes), static_cast<bool>(joverwrite_key));
   return reinterpret_cast<jlong>(wbwi);
 }
 
@@ -241,7 +241,7 @@ void Java_org_rocksdb_WriteBatchWithIndex_rollbackToSavePoint0(
 jlong Java_org_rocksdb_WriteBatchWithIndex_iterator0(
     JNIEnv* env, jobject jobj, jlong jwbwi_handle) {
   auto* wbwi = reinterpret_cast<rocksdb::WriteBatchWithIndex*>(jwbwi_handle);
-  rocksdb::WBWIIterator* wbwi_iterator = wbwi->NewIterator();
+  auto* wbwi_iterator = wbwi->NewIterator();
   return reinterpret_cast<jlong>(wbwi_iterator);
 }
 
@@ -254,7 +254,7 @@ jlong Java_org_rocksdb_WriteBatchWithIndex_iterator1(
     JNIEnv* env, jobject jobj, jlong jwbwi_handle, jlong jcf_handle) {
   auto* wbwi = reinterpret_cast<rocksdb::WriteBatchWithIndex*>(jwbwi_handle);
   auto* cf_handle = reinterpret_cast<rocksdb::ColumnFamilyHandle*>(jcf_handle);
-  rocksdb::WBWIIterator* wbwi_iterator = wbwi->NewIterator(cf_handle);
+  auto* wbwi_iterator = wbwi->NewIterator(cf_handle);
   return reinterpret_cast<jlong>(wbwi_iterator);
 }
 
@@ -362,6 +362,7 @@ jbyteArray Java_org_rocksdb_WriteBatchWithIndex_getFromBatchAndDB__JJJ_3BIJ(
 void Java_org_rocksdb_WriteBatchWithIndex_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
   auto* wbwi = reinterpret_cast<rocksdb::WriteBatchWithIndex*>(handle);
+  assert(wbwi != nullptr);
   delete wbwi;
 }
 
@@ -375,6 +376,7 @@ void Java_org_rocksdb_WriteBatchWithIndex_disposeInternal(
 void Java_org_rocksdb_WBWIRocksIterator_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
   auto* it = reinterpret_cast<rocksdb::WBWIIterator*>(handle);
+  assert(it != nullptr);
   delete it;
 }
 
@@ -437,7 +439,12 @@ void Java_org_rocksdb_WBWIRocksIterator_seek0(
     JNIEnv* env, jobject jobj, jlong handle, jbyteArray jtarget,
     jint jtarget_len) {
   auto* it = reinterpret_cast<rocksdb::WBWIIterator*>(handle);
-  jbyte* target = env->GetByteArrayElements(jtarget, 0);
+  jbyte* target = env->GetByteArrayElements(jtarget, nullptr);
+  if(target == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+
   rocksdb::Slice target_slice(
       reinterpret_cast<char*>(target), jtarget_len);
 
@@ -497,26 +504,41 @@ jlongArray Java_org_rocksdb_WBWIRocksIterator_entry1(
       results[0] = 0x0;
   }
 
-  //TODO(AR) do we leak buf and value_buf?
+  // key_slice and value_slice will be freed by org.rocksdb.DirectSlice#close
 
-  //set the pointer to the key slice
+  auto* key_slice = new rocksdb::Slice(we.key.data(), we.key.size());
-  char* buf = new char[we.key.size()];
-  memcpy(buf, we.key.data(), we.key.size());
-  auto* key_slice = new rocksdb::Slice(buf, we.key.size());
   results[1] = reinterpret_cast<jlong>(key_slice);
-
+  if (we.type == rocksdb::kDeleteRecord
-  //set the pointer to the value slice
+      || we.type == rocksdb::kLogDataRecord) {
-  if (we.type == rocksdb::kDeleteRecord || we.type == rocksdb::kLogDataRecord) {
     // set native handle of value slice to null if no value available
     results[2] = 0;
   } else {
-    char* value_buf = new char[we.value.size()];
+    auto* value_slice = new rocksdb::Slice(we.value.data(), we.value.size());
-    memcpy(value_buf, we.value.data(), we.value.size());
-    auto* value_slice = new rocksdb::Slice(value_buf, we.value.size());
     results[2] = reinterpret_cast<jlong>(value_slice);
   }
 
   jlongArray jresults = env->NewLongArray(3);
+  if(jresults == nullptr) {
+    // exception thrown: OutOfMemoryError
+    if(results[2] != 0) {
+      auto* value_slice = reinterpret_cast<rocksdb::Slice*>(results[2]);
+      delete value_slice;
+    }
+    delete key_slice;
+    return nullptr;
+  }
+
   env->SetLongArrayRegion(jresults, 0, 3, results);
+  if(env->ExceptionCheck()) {
+    // exception thrown: ArrayIndexOutOfBoundsException
+    env->DeleteLocalRef(jresults);
+    if(results[2] != 0) {
+      auto* value_slice = reinterpret_cast<rocksdb::Slice*>(results[2]);
+      delete value_slice;
+    }
+    delete key_slice;
+    return nullptr;
+  }
+
   return jresults;
 }

java/rocksjni/writebatchhandlerjnicallback.cc

@@ -16,69 +16,202 @@ WriteBatchHandlerJniCallback::WriteBatchHandlerJniCallback(
 
   // Note: we want to access the Java WriteBatchHandler instance
   // across multiple method calls, so we create a global ref
+  assert(jWriteBatchHandler != nullptr);
   m_jWriteBatchHandler = env->NewGlobalRef(jWriteBatchHandler);
+  if(m_jWriteBatchHandler == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
 
   m_jPutMethodId = WriteBatchHandlerJni::getPutMethodId(env);
+  if(m_jPutMethodId == nullptr) {
+    // exception thrown
+    return;
+  }
+
   m_jMergeMethodId = WriteBatchHandlerJni::getMergeMethodId(env);
+  if(m_jMergeMethodId == nullptr) {
+    // exception thrown
+    return;
+  }
+
   m_jDeleteMethodId = WriteBatchHandlerJni::getDeleteMethodId(env);
+  if(m_jDeleteMethodId == nullptr) {
+    // exception thrown
+    return;
+  }
+
   m_jLogDataMethodId = WriteBatchHandlerJni::getLogDataMethodId(env);
+  if(m_jLogDataMethodId == nullptr) {
+    // exception thrown
+    return;
+  }
+
   m_jContinueMethodId = WriteBatchHandlerJni::getContinueMethodId(env);
+  if(m_jContinueMethodId == nullptr) {
+    // exception thrown
+    return;
+  }
 }
 
 void WriteBatchHandlerJniCallback::Put(const Slice& key, const Slice& value) {
   const jbyteArray j_key = sliceToJArray(key);
+  if(j_key == nullptr) {
+    // exception thrown
+    if(m_env->ExceptionCheck()) {
+      m_env->ExceptionDescribe();
+    }
+    return;
+  }
+
   const jbyteArray j_value = sliceToJArray(value);
+  if(j_value == nullptr) {
+    // exception thrown
+    if(m_env->ExceptionCheck()) {
+      m_env->ExceptionDescribe();
+    }
+    if(j_key != nullptr) {
+      m_env->DeleteLocalRef(j_key);
+    }
+    return;
+  }
 
   m_env->CallVoidMethod(
       m_jWriteBatchHandler,
       m_jPutMethodId,
       j_key,
       j_value);
+  if(m_env->ExceptionCheck()) {
+    // exception thrown
+    m_env->ExceptionDescribe();
+    if(j_value != nullptr) {
+      m_env->DeleteLocalRef(j_value);
+    }
+    if(j_key != nullptr) {
+      m_env->DeleteLocalRef(j_key);
+    }
+    return;
+  }
 
-  m_env->DeleteLocalRef(j_value);
+  if(j_value != nullptr) {
-  m_env->DeleteLocalRef(j_key);
+    m_env->DeleteLocalRef(j_value);
+  }
+  if(j_key != nullptr) {
+    m_env->DeleteLocalRef(j_key);
+  }
 }
 
 void WriteBatchHandlerJniCallback::Merge(const Slice& key, const Slice& value) {
   const jbyteArray j_key = sliceToJArray(key);
+  if(j_key == nullptr) {
+    // exception thrown
+    if(m_env->ExceptionCheck()) {
+      m_env->ExceptionDescribe();
+    }
+    return;
+  }
+
   const jbyteArray j_value = sliceToJArray(value);
+  if(j_value == nullptr) {
+    // exception thrown
+    if(m_env->ExceptionCheck()) {
+      m_env->ExceptionDescribe();
+    }
+    if(j_key != nullptr) {
+      m_env->DeleteLocalRef(j_key);
+    }
+    return;
+  }
 
   m_env->CallVoidMethod(
       m_jWriteBatchHandler,
       m_jMergeMethodId,
       j_key,
       j_value);
+  if(m_env->ExceptionCheck()) {
+    // exception thrown
+    m_env->ExceptionDescribe();
+    if(j_value != nullptr) {
+      m_env->DeleteLocalRef(j_value);
+    }
+    if(j_key != nullptr) {
+      m_env->DeleteLocalRef(j_key);
+    }
+    return;
+  }
 
-  m_env->DeleteLocalRef(j_value);
+  if(j_value != nullptr) {
-  m_env->DeleteLocalRef(j_key);
+    m_env->DeleteLocalRef(j_value);
+  }
+  if(j_key != nullptr) {
+    m_env->DeleteLocalRef(j_key);
+  }
 }
 
 void WriteBatchHandlerJniCallback::Delete(const Slice& key) {
   const jbyteArray j_key = sliceToJArray(key);
+  if(j_key == nullptr) {
+    // exception thrown
+    if(m_env->ExceptionCheck()) {
+      m_env->ExceptionDescribe();
+    }
+    return;
+  }
 
   m_env->CallVoidMethod(
       m_jWriteBatchHandler,
       m_jDeleteMethodId,
       j_key);
+  if(m_env->ExceptionCheck()) {
+    // exception thrown
+    m_env->ExceptionDescribe();
+    if(j_key != nullptr) {
+      m_env->DeleteLocalRef(j_key);
+    }
+    return;
+  }
 
-  m_env->DeleteLocalRef(j_key);
+  if(j_key != nullptr) {
+    m_env->DeleteLocalRef(j_key);
+  }
 }
 
 void WriteBatchHandlerJniCallback::LogData(const Slice& blob) {
   const jbyteArray j_blob = sliceToJArray(blob);
+  if(j_blob == nullptr) {
+    // exception thrown
+    if(m_env->ExceptionCheck()) {
+      m_env->ExceptionDescribe();
+    }
+    return;
+  }
 
   m_env->CallVoidMethod(
       m_jWriteBatchHandler,
       m_jLogDataMethodId,
       j_blob);
+  if(m_env->ExceptionCheck()) {
+    // exception thrown
+    m_env->ExceptionDescribe();
+    if(j_blob != nullptr) {
+      m_env->DeleteLocalRef(j_blob);
+    }
+    return;
+  }
 
-  m_env->DeleteLocalRef(j_blob);
+  if(j_blob != nullptr) {
+    m_env->DeleteLocalRef(j_blob);
+  }
 }
 
 bool WriteBatchHandlerJniCallback::Continue() {
   jboolean jContinue = m_env->CallBooleanMethod(
       m_jWriteBatchHandler,
       m_jContinueMethodId);
+  if(m_env->ExceptionCheck()) {
+    // exception thrown
+    m_env->ExceptionDescribe();
+  }
 
   return static_cast<bool>(jContinue == JNI_TRUE);
 }
@@ -89,16 +222,36 @@ bool WriteBatchHandlerJniCallback::Continue() {
  * When calling this function
  * you must remember to call env->DeleteLocalRef
  * on the result after you have finished with it
+ *
+ * @param s A Slice to convery to a Java byte array
+ *
+ * @return A reference to a Java byte array, or a nullptr if an
+ *     exception occurs
  */
 jbyteArray WriteBatchHandlerJniCallback::sliceToJArray(const Slice& s) {
   jbyteArray ja = m_env->NewByteArray(static_cast<jsize>(s.size()));
+  if(ja == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return nullptr;
+  }
+
   m_env->SetByteArrayRegion(
       ja, 0, static_cast<jsize>(s.size()),
       reinterpret_cast<const jbyte*>(s.data()));
+  if(m_env->ExceptionCheck()) {
+    if(ja != nullptr) {
+      m_env->DeleteLocalRef(ja);
+    }
+    // exception thrown: ArrayIndexOutOfBoundsException
+    return nullptr;
+  }
+
   return ja;
 }
 
 WriteBatchHandlerJniCallback::~WriteBatchHandlerJniCallback() {
-  m_env->DeleteGlobalRef(m_jWriteBatchHandler);
+  if(m_jWriteBatchHandler != nullptr) {
+    m_env->DeleteGlobalRef(m_jWriteBatchHandler);
+  }
 }
 }  // namespace rocksdb

java/samples/src/main/java/RocksDBColumnFamilySample.java

@@ -13,13 +13,14 @@ public class RocksDBColumnFamilySample {
     RocksDB.loadLibrary();
   }
 
-  public static void main(String[] args) throws RocksDBException {
+  public static void main(final String[] args) throws RocksDBException {
     if (args.length < 1) {
       System.out.println(
           "usage: RocksDBColumnFamilySample db_path");
-      return;
+      System.exit(-1);
     }
-    String db_path = args[0];
+
+    final String db_path = args[0];
 
     System.out.println("RocksDBColumnFamilySample");
     try(final Options options = new Options().setCreateIfMissing(true);
@@ -54,8 +55,6 @@ public class RocksDBColumnFamilySample {
         // put and get from non-default column family
         db.put(columnFamilyHandles.get(0), new WriteOptions(),
             "key".getBytes(), "value".getBytes());
-        String value = new String(db.get(columnFamilyHandles.get(0),
-            "key".getBytes()));
 
         // atomic write
         try (final WriteBatch wb = new WriteBatch()) {

java/samples/src/main/java/RocksDBSample.java

@@ -12,31 +12,31 @@ import java.util.ArrayList;
 import org.rocksdb.*;
 import org.rocksdb.util.SizeUnit;
 
-import java.io.IOException;
-
 public class RocksDBSample {
   static {
     RocksDB.loadLibrary();
   }
 
-  public static void main(String[] args) {
+  public static void main(final String[] args) {
     if (args.length < 1) {
       System.out.println("usage: RocksDBSample db_path");
-      return;
+      System.exit(-1);
     }
-    String db_path = args[0];
+
-    String db_path_not_found = db_path + "_not_found";
+    final String db_path = args[0];
+    final String db_path_not_found = db_path + "_not_found";
 
     System.out.println("RocksDBSample");
     try (final Options options = new Options();
          final Filter bloomFilter = new BloomFilter(10);
          final ReadOptions readOptions = new ReadOptions()
-             .setFillCache(false)) {
+             .setFillCache(false);
+         final RateLimiter rateLimiter = new RateLimiter(10000000,10000, 10)) {
 
       try (final RocksDB db = RocksDB.open(options, db_path_not_found)) {
         assert (false);
-      } catch (RocksDBException e) {
+      } catch (final RocksDBException e) {
-        System.out.format("caught the expected exception -- %s\n", e);
+        System.out.format("Caught the expected exception -- %s\n", e);
       }
 
       try {
@@ -47,11 +47,11 @@ public class RocksDBSample {
             .setMaxBackgroundCompactions(10)
             .setCompressionType(CompressionType.SNAPPY_COMPRESSION)
             .setCompactionStyle(CompactionStyle.UNIVERSAL);
-      } catch (IllegalArgumentException e) {
+      } catch (final IllegalArgumentException e) {
         assert (false);
       }
 
-      Statistics stats = options.statisticsPtr();
+      final Statistics stats = options.statisticsPtr();
 
       assert (options.createIfMissing() == true);
       assert (options.writeBufferSize() == 8 * SizeUnit.KB);
@@ -85,9 +85,7 @@ public class RocksDBSample {
       options.setAllowMmapReads(true);
       assert (options.tableFactoryName().equals("PlainTable"));
 
-      options.setRateLimiterConfig(new GenericRateLimiterConfig(10000000,
+      options.setRateLimiter(rateLimiter);
-          10000, 10));
-      options.setRateLimiterConfig(new GenericRateLimiterConfig(10000000));
 
       final BlockBasedTableConfig table_options = new BlockBasedTableConfig();
       table_options.setBlockCacheSize(64 * SizeUnit.KB)
@@ -114,12 +112,14 @@ public class RocksDBSample {
 
       try (final RocksDB db = RocksDB.open(options, db_path)) {
         db.put("hello".getBytes(), "world".getBytes());
-        byte[] value = db.get("hello".getBytes());
+
+        final byte[] value = db.get("hello".getBytes());
         assert ("world".equals(new String(value)));
-        String str = db.getProperty("rocksdb.stats");
+
+        final String str = db.getProperty("rocksdb.stats");
         assert (str != null && !str.equals(""));
-      } catch (RocksDBException e) {
+      } catch (final RocksDBException e) {
-        System.out.format("[ERROR] caught the unexpceted exception -- %s\n", e);
+        System.out.format("[ERROR] caught the unexpected exception -- %s\n", e);
         assert (false);
       }
 
@@ -174,8 +174,8 @@ public class RocksDBSample {
         value = db.get(readOptions, "world".getBytes());
         assert (value == null);
 
-        byte[] testKey = "asdf".getBytes();
+        final byte[] testKey = "asdf".getBytes();
-        byte[] testValue =
+        final byte[] testValue =
             "asdfghjkl;'?><MNBVCXZQWERTYUIOP{+_)(*&^%$#@".getBytes();
         db.put(testKey, testValue);
         byte[] testResult = db.get(testKey);
@@ -187,8 +187,8 @@ public class RocksDBSample {
         assert (Arrays.equals(testValue, testResult));
         assert (new String(testValue).equals(new String(testResult)));
 
-        byte[] insufficientArray = new byte[10];
+        final byte[] insufficientArray = new byte[10];
-        byte[] enoughArray = new byte[50];
+        final byte[] enoughArray = new byte[50];
         int len;
         len = db.get(testKey, insufficientArray);
         assert (len > insufficientArray.length);
@@ -220,21 +220,21 @@ public class RocksDBSample {
         }
 
         try {
-          for (TickerType statsType : TickerType.values()) {
+          for (final TickerType statsType : TickerType.values()) {
             stats.getTickerCount(statsType);
           }
           System.out.println("getTickerCount() passed.");
-        } catch (Exception e) {
+        } catch (final Exception e) {
           System.out.println("Failed in call to getTickerCount()");
           assert (false); //Should never reach here.
         }
 
         try {
-          for (HistogramType histogramType : HistogramType.values()) {
+          for (final HistogramType histogramType : HistogramType.values()) {
             HistogramData data = stats.getHistogramData(histogramType);
           }
           System.out.println("getHistogramData() passed.");
-        } catch (Exception e) {
+        } catch (final Exception e) {
           System.out.println("Failed in call to getHistogramData()");
           assert (false); //Should never reach here.
         }
@@ -283,16 +283,16 @@ public class RocksDBSample {
 
         Map<byte[], byte[]> values = db.multiGet(keys);
         assert (values.size() == keys.size());
-        for (byte[] value1 : values.values()) {
+        for (final byte[] value1 : values.values()) {
           assert (value1 != null);
         }
 
         values = db.multiGet(new ReadOptions(), keys);
         assert (values.size() == keys.size());
-        for (byte[] value1 : values.values()) {
+        for (final byte[] value1 : values.values()) {
           assert (value1 != null);
         }
-      } catch (RocksDBException e) {
+      } catch (final RocksDBException e) {
         System.err.println(e);
       }
     }

java/src/main/java/org/rocksdb/AbstractSlice.java

@@ -57,6 +57,20 @@ public abstract class AbstractSlice<T> extends RocksMutableObject {
    */
   protected abstract T data0(long handle);
 
+  /**
+   * Drops the specified {@code n}
+   * number of bytes from the start
+   * of the backing slice
+   *
+   * @param n The number of bytes to drop
+   */
+  public abstract void removePrefix(final int n);
+
+  /**
+   * Clears the backing slice
+   */
+  public abstract void clear();
+
   /**
    * Return the length (in bytes) of the data.
    *

java/src/main/java/org/rocksdb/ColumnFamilyOptions.java

@@ -143,7 +143,7 @@ public class ColumnFamilyOptions extends RocksObject
   @Override
   public ColumnFamilyOptions setMergeOperator(
       final MergeOperator mergeOperator) {
-    setMergeOperator(nativeHandle_, mergeOperator.newMergeOperatorHandle());
+    setMergeOperator(nativeHandle_, mergeOperator.nativeHandle_);
     return this;
   }
 

java/src/main/java/org/rocksdb/DBOptions.java

@@ -134,15 +134,6 @@ public class DBOptions extends RocksObject implements DBOptionsInterface {
     return paranoidChecks(nativeHandle_);
   }
 
-  @Override
-  public DBOptions setRateLimiterConfig(
-      final RateLimiterConfig config) {
-    assert(isOwningHandle());
-    rateLimiterConfig_ = config;
-    setOldRateLimiter(nativeHandle_, config.newRateLimiterHandle());
-    return this;
-  }
-
   @Override
   public DBOptions setRateLimiter(final RateLimiter rateLimiter) {
     assert(isOwningHandle());
@@ -650,9 +641,6 @@ public long delayedWriteRate(){
   private native void setParanoidChecks(
       long handle, boolean paranoidChecks);
   private native boolean paranoidChecks(long handle);
-  @Deprecated
-  private native void setOldRateLimiter(long handle,
-      long rateLimiterHandle);
   private native void setRateLimiter(long handle,
       long rateLimiterHandle);
   private native void setLogger(long handle,
@@ -750,6 +738,5 @@ public long delayedWriteRate(){
   private native long delayedWriteRate(long handle);
 
   int numShardBits_;
-  RateLimiterConfig rateLimiterConfig_;
   RateLimiter rateLimiter_;
 }

java/src/main/java/org/rocksdb/DBOptionsInterface.java

@@ -118,18 +118,6 @@ public interface DBOptionsInterface {
    */
   boolean paranoidChecks();
 
-  /**
-   * Use to control write rate of flush and compaction. Flush has higher
-   * priority than compaction. Rate limiting is disabled if nullptr.
-   * Default: nullptr
-   *
-   * @param config rate limiter config.
-   * @return the instance of the current Object.
-   * @deprecated See: {@link #setRateLimiter(RateLimiter)}.
-   */
-  @Deprecated
-  Object setRateLimiterConfig(RateLimiterConfig config);
-
   /**
    * Use to control write rate of flush and compaction. Flush has higher
    * priority than compaction. Rate limiting is disabled if nullptr.

java/src/main/java/org/rocksdb/DirectSlice.java

@@ -18,6 +18,13 @@ import java.nio.ByteBuffer;
 public class DirectSlice extends AbstractSlice<ByteBuffer> {
   public final static DirectSlice NONE = new DirectSlice();
 
+  /**
+   * Indicates whether we have to free the memory pointed to by the Slice
+   */
+  private final boolean internalBuffer;
+  private volatile boolean cleared = false;
+  private volatile long internalBufferOffset = 0;
+
   /**
    * Called from JNI to construct a new Java DirectSlice
    * without an underlying C++ object set
@@ -32,6 +39,7 @@ public class DirectSlice extends AbstractSlice<ByteBuffer> {
    */
   DirectSlice() {
     super();
+    this.internalBuffer = false;
   }
 
   /**
@@ -43,6 +51,7 @@ public class DirectSlice extends AbstractSlice<ByteBuffer> {
    */
   public DirectSlice(final String str) {
     super(createNewSliceFromString(str));
+    this.internalBuffer = true;
   }
 
   /**
@@ -55,6 +64,7 @@ public class DirectSlice extends AbstractSlice<ByteBuffer> {
    */
   public DirectSlice(final ByteBuffer data, final int length) {
     super(createNewDirectSlice0(ensureDirect(data), length));
+    this.internalBuffer = false;
   }
 
   /**
@@ -66,12 +76,13 @@ public class DirectSlice extends AbstractSlice<ByteBuffer> {
    */
   public DirectSlice(final ByteBuffer data) {
     super(createNewDirectSlice1(ensureDirect(data)));
+    this.internalBuffer = false;
   }
 
   private static ByteBuffer ensureDirect(final ByteBuffer data) {
-    // TODO(AR) consider throwing a checked exception, as if it's not direct
+    if(!data.isDirect()) {
-    // this can SIGSEGV
+      throw new IllegalArgumentException("The ByteBuffer must be direct");
-    assert(data.isDirect());
+    }
     return data;
   }
 
@@ -83,26 +94,29 @@ public class DirectSlice extends AbstractSlice<ByteBuffer> {
    *
    * @return the requested byte
    */
-  public byte get(int offset) {
+  public byte get(final int offset) {
     return get0(getNativeHandle(), offset);
   }
 
-  /**
+  @Override
-   * Clears the backing slice
-   */
   public void clear() {
-    clear0(getNativeHandle());
+    clear0(getNativeHandle(), !cleared && internalBuffer, internalBufferOffset);
+    cleared = true;
   }
 
-  /**
+  @Override
-   * Drops the specified {@code n}
-   * number of bytes from the start
-   * of the backing slice
-   *
-   * @param n The number of bytes to drop
-   */
   public void removePrefix(final int n) {
     removePrefix0(getNativeHandle(), n);
+    this.internalBufferOffset += n;
+  }
+
+  @Override
+  protected void disposeInternal() {
+    final long nativeHandle = getNativeHandle();
+    if(!cleared && internalBuffer) {
+      disposeInternalBuf(nativeHandle, internalBufferOffset);
+    }
+    disposeInternal(nativeHandle);
   }
 
   private native static long createNewDirectSlice0(final ByteBuffer data,
@@ -110,6 +124,9 @@ public class DirectSlice extends AbstractSlice<ByteBuffer> {
   private native static long createNewDirectSlice1(final ByteBuffer data);
   @Override protected final native ByteBuffer data0(long handle);
   private native byte get0(long handle, int offset);
-  private native void clear0(long handle);
+  private native void clear0(long handle, boolean internalBuffer,
+      long internalBufferOffset);
   private native void removePrefix0(long handle, int length);
+  private native void disposeInternalBuf(final long handle,
+      long internalBufferOffset);
 }

java/src/main/java/org/rocksdb/EnvOptions.java

@@ -134,15 +134,15 @@ public class EnvOptions extends RocksObject {
     return writableFileMaxBufferSize(nativeHandle_);
   }
 
-  public EnvOptions setRateLimiterConfig(final RateLimiterConfig rateLimiterConfig) {
+  public EnvOptions setRateLimiter(final RateLimiter rateLimiter) {
-    this.rateLimiterConfig = rateLimiterConfig;
+    this.rateLimiter = rateLimiter;
-    setRateLimiter(nativeHandle_, rateLimiterConfig.newRateLimiterHandle());
+    setRateLimiter(nativeHandle_, rateLimiter.nativeHandle_);
     return this;
   }
 
-  public RateLimiterConfig rateLimiterConfig() {
+  public RateLimiter rateLimiter() {
     assert(isOwningHandle());
-    return rateLimiterConfig;
+    return rateLimiter;
   }
 
   private native static long newEnvOptions();
@@ -203,5 +203,5 @@ public class EnvOptions extends RocksObject {
 
   private native void setRateLimiter(final long handle, final long rateLimiterHandle);
 
-  private RateLimiterConfig rateLimiterConfig;
+  private RateLimiter rateLimiter;
 }

java/src/main/java/org/rocksdb/GenericRateLimiterConfig.java

@@ -1,68 +0,0 @@
-// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
-// This source code is licensed under the BSD-style license found in the
-// LICENSE file in the root directory of this source tree. An additional grant
-// of patent rights can be found in the PATENTS file in the same directory.
-package org.rocksdb;
-
-/**
- * Config for rate limiter, which is used to control write rate of flush and
- * compaction.
- *
- * @see RateLimiterConfig
- * @deprecated obsolete. See: {@link org.rocksdb.RateLimiter}.
- */
-@Deprecated
-public class GenericRateLimiterConfig extends RateLimiterConfig {
-  private static final long DEFAULT_REFILL_PERIOD_MICROS = (100 * 1000);
-  private static final int DEFAULT_FAIRNESS = 10;
-
-  /**
-   * GenericRateLimiterConfig constructor
-   *
-   * @param rateBytesPerSecond this is the only parameter you want to set
-   *     most of the time. It controls the total write rate of compaction
-   *     and flush in bytes per second. Currently, RocksDB does not enforce
-   *     rate limit for anything other than flush and compaction, e.g. write to WAL.
-   * @param refillPeriodMicros this controls how often tokens are refilled. For example,
-   *     when rate_bytes_per_sec is set to 10MB/s and refill_period_us is set to
-   *     100ms, then 1MB is refilled every 100ms internally. Larger value can lead to
-   *     burstier writes while smaller value introduces more CPU overhead.
-   *     The default should work for most cases.
-   * @param fairness RateLimiter accepts high-pri requests and low-pri requests.
-   *     A low-pri request is usually blocked in favor of hi-pri request. Currently,
-   *     RocksDB assigns low-pri to request from compaction and high-pri to request
-   *     from flush. Low-pri requests can get blocked if flush requests come in
-   *     continuously. This fairness parameter grants low-pri requests permission by
-   *     fairness chance even though high-pri requests exist to avoid starvation.
-   *     You should be good by leaving it at default 10.
-   */
-  public GenericRateLimiterConfig(final long rateBytesPerSecond,
-      final long refillPeriodMicros, final int fairness) {
-    rateBytesPerSecond_ = rateBytesPerSecond;
-    refillPeriodMicros_ = refillPeriodMicros;
-    fairness_ = fairness;
-  }
-
-  /**
-   * GenericRateLimiterConfig constructor
-   *
-   * @param rateBytesPerSecond this is the only parameter you want to set
-   *     most of the time. It controls the total write rate of compaction
-   *     and flush in bytes per second. Currently, RocksDB does not enforce
-   *     rate limit for anything other than flush and compaction, e.g. write to WAL.
-   */
-  public GenericRateLimiterConfig(final long rateBytesPerSecond) {
-    this(rateBytesPerSecond, DEFAULT_REFILL_PERIOD_MICROS, DEFAULT_FAIRNESS);
-  }
-
-  @Override protected long newRateLimiterHandle() {
-    return newRateLimiterHandle(rateBytesPerSecond_, refillPeriodMicros_,
-        fairness_);
-  }
-
-  private native long newRateLimiterHandle(long rateBytesPerSecond,
-      long refillPeriodMicros, int fairness);
-  private final long rateBytesPerSecond_;
-  private final long refillPeriodMicros_;
-  private final int fairness_;
-}

java/src/main/java/org/rocksdb/MergeOperator.java

@@ -10,6 +10,8 @@ package org.rocksdb;
  * two merge operands held under the same key in order to obtain a single
  * value.
  */
-public interface MergeOperator {
+public abstract class MergeOperator extends RocksObject {
-    long newMergeOperatorHandle();
+    protected MergeOperator(final long nativeHandle) {
+        super(nativeHandle);
+    }
 }

java/src/main/java/org/rocksdb/MutableColumnFamilyOptions.java

@@ -49,6 +49,10 @@ public class MutableColumnFamilyOptions {
    * For int[] values, each int should be separated by a comma, e.g.
    *
    * key1=value1;intArrayKey1=1,2,3
+   *
+   * @param str The string representation of the mutable column family options
+   *
+   * @return A builder for the mutable column family options
    */
   public static MutableColumnFamilyOptionsBuilder parse(final String str) {
     Objects.requireNonNull(str);

java/src/main/java/org/rocksdb/Options.java

@@ -188,7 +188,7 @@ public class Options extends RocksObject
 
   @Override
   public Options setMergeOperator(final MergeOperator mergeOperator) {
-    setMergeOperator(nativeHandle_, mergeOperator.newMergeOperatorHandle());
+    setMergeOperator(nativeHandle_, mergeOperator.nativeHandle_);
     return this;
   }
 
@@ -683,13 +683,6 @@ public class Options extends RocksObject
     return this;
   }
 
-  @Override
-  public Options setRateLimiterConfig(final RateLimiterConfig config) {
-    rateLimiterConfig_ = config;
-    setOldRateLimiter(nativeHandle_, config.newRateLimiterHandle());
-    return this;
-  }
-
   @Override
   public Options setRateLimiter(final RateLimiter rateLimiter) {
     assert(isOwningHandle());
@@ -1202,9 +1195,6 @@ public class Options extends RocksObject
   private native void setParanoidChecks(
       long handle, boolean paranoidChecks);
   private native boolean paranoidChecks(long handle);
-  @Deprecated
-  private native void setOldRateLimiter(long handle,
-      long rateLimiterHandle);
   private native void setRateLimiter(long handle,
       long rateLimiterHandle);
   private native void setLogger(long handle,
@@ -1436,7 +1426,6 @@ public class Options extends RocksObject
   Env env_;
   MemTableConfig memTableConfig_;
   TableFormatConfig tableFormatConfig_;
-  RateLimiterConfig rateLimiterConfig_;
   RateLimiter rateLimiter_;
   AbstractComparator<? extends AbstractSlice<?>> comparator_;
 }

java/src/main/java/org/rocksdb/RateLimiterConfig.java

@@ -1,26 +0,0 @@
-// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
-// This source code is licensed under the BSD-style license found in the
-// LICENSE file in the root directory of this source tree. An additional grant
-// of patent rights can be found in the PATENTS file in the same directory.
-package org.rocksdb;
-
-/**
- * Config for rate limiter, which is used to control write rate of flush and
- * compaction.
- *
- * @deprecated obsolete. See: {@link org.rocksdb.RateLimiter}.
- */
-@Deprecated
-public abstract class RateLimiterConfig {
-  /**
-   * This function should only be called by
-   * {@link org.rocksdb.DBOptions#setRateLimiter(long, long)}, which will
-   * create a c++ shared-pointer to the c++ {@code RateLimiter} that is associated
-   * with a Java RateLimiterConfig.
-   *
-   * @see org.rocksdb.DBOptions#setRateLimiter(long, long)
-   *
-   * @return native handle address to rate limiter instance.
-   */
-  abstract protected long newRateLimiterHandle();
-}

java/src/main/java/org/rocksdb/RocksDB.java

@@ -520,11 +520,11 @@ public class RocksDB extends RocksObject {
    * to make this lighter weight is to avoid doing any IOs.
    *
    * @param key byte array of a key to search for
-   * @param value StringBuffer instance which is a out parameter if a value is
+   * @param value StringBuilder instance which is a out parameter if a value is
    *    found in block-cache.
    * @return boolean value indicating if key does not exist or might exist.
    */
-  public boolean keyMayExist(final byte[] key, final StringBuffer value) {
+  public boolean keyMayExist(final byte[] key, final StringBuilder value) {
     return keyMayExist(nativeHandle_, key, 0, key.length, value);
   }
 
@@ -537,12 +537,12 @@ public class RocksDB extends RocksObject {
    *
    * @param columnFamilyHandle {@link ColumnFamilyHandle} instance
    * @param key byte array of a key to search for
-   * @param value StringBuffer instance which is a out parameter if a value is
+   * @param value StringBuilder instance which is a out parameter if a value is
    *    found in block-cache.
    * @return boolean value indicating if key does not exist or might exist.
    */
   public boolean keyMayExist(final ColumnFamilyHandle columnFamilyHandle,
-      final byte[] key, final StringBuffer value) {
+      final byte[] key, final StringBuilder value) {
     return keyMayExist(nativeHandle_, key, 0, key.length,
         columnFamilyHandle.nativeHandle_, value);
   }
@@ -556,12 +556,12 @@ public class RocksDB extends RocksObject {
    *
    * @param readOptions {@link ReadOptions} instance
    * @param key byte array of a key to search for
-   * @param value StringBuffer instance which is a out parameter if a value is
+   * @param value StringBuilder instance which is a out parameter if a value is
    *    found in block-cache.
    * @return boolean value indicating if key does not exist or might exist.
    */
   public boolean keyMayExist(final ReadOptions readOptions,
-      final byte[] key, final StringBuffer value) {
+      final byte[] key, final StringBuilder value) {
     return keyMayExist(nativeHandle_, readOptions.nativeHandle_,
         key, 0, key.length, value);
   }
@@ -576,13 +576,13 @@ public class RocksDB extends RocksObject {
    * @param readOptions {@link ReadOptions} instance
    * @param columnFamilyHandle {@link ColumnFamilyHandle} instance
    * @param key byte array of a key to search for
-   * @param value StringBuffer instance which is a out parameter if a value is
+   * @param value StringBuilder instance which is a out parameter if a value is
    *    found in block-cache.
    * @return boolean value indicating if key does not exist or might exist.
    */
   public boolean keyMayExist(final ReadOptions readOptions,
       final ColumnFamilyHandle columnFamilyHandle, final byte[] key,
-      final StringBuffer value) {
+      final StringBuilder value) {
     return keyMayExist(nativeHandle_, readOptions.nativeHandle_,
         key, 0, key.length, columnFamilyHandle.nativeHandle_,
         value);
@@ -685,6 +685,9 @@ public class RocksDB extends RocksObject {
         columnFamilyHandle.nativeHandle_);
   }
 
+  // TODO(AR) we should improve the #get() API, returning -1 (RocksDB.NOT_FOUND) is not very nice
+  // when we could communicate better status into, also the C++ code show that -2 could be returned
+
   /**
    * Get the value associated with the specified key within column family*
    * @param key the key to retrieve the value.
@@ -1917,6 +1920,8 @@ public class RocksDB extends RocksObject {
    * This function will wait until all currently running background processes
    * finish. After it returns, no background process will be run until
    * {@link #continueBackgroundWork()} is called
+   *
+   * @throws RocksDBException If an error occurs when pausing background work
    */
   public void pauseBackgroundWork() throws RocksDBException {
     pauseBackgroundWork(nativeHandle_);
@@ -1925,6 +1930,8 @@ public class RocksDB extends RocksObject {
   /**
    * Resumes backround work which was suspended by
    * previously calling {@link #pauseBackgroundWork()}
+   *
+   * @throws RocksDBException If an error occurs when resuming background work
    */
   public void continueBackgroundWork() throws RocksDBException {
     continueBackgroundWork(nativeHandle_);
@@ -2182,17 +2189,17 @@ public class RocksDB extends RocksObject {
       long wbwiHandle) throws RocksDBException;
   protected native boolean keyMayExist(final long handle, final byte[] key,
       final int keyOffset, final int keyLength,
-      final StringBuffer stringBuffer);
+      final StringBuilder stringBuilder);
   protected native boolean keyMayExist(final long handle, final byte[] key,
       final int keyOffset, final int keyLength, final long cfHandle,
-      final StringBuffer stringBuffer);
+      final StringBuilder stringBuilder);
   protected native boolean keyMayExist(final long handle,
       final long optionsHandle, final byte[] key, final int keyOffset,
-      final int keyLength, final StringBuffer stringBuffer);
+      final int keyLength, final StringBuilder stringBuilder);
   protected native boolean keyMayExist(final long handle,
       final long optionsHandle, final byte[] key, final int keyOffset,
       final int keyLength, final long cfHandle,
-      final StringBuffer stringBuffer);
+      final StringBuilder stringBuilder);
   protected native void merge(long handle, byte[] key, int keyOffset,
       int keyLength, byte[] value, int valueOffset, int valueLength)
       throws RocksDBException;

java/src/main/java/org/rocksdb/RocksMutableObject.java

@@ -30,6 +30,24 @@ public abstract class RocksMutableObject extends AbstractNativeReference {
     this.owningHandle_ = true;
   }
 
+  /**
+   * Closes the existing handle, and changes the handle to the new handle
+   *
+   * @param newNativeHandle The C++ pointer to the new native object
+   * @param owningNativeHandle true if we own the new native object
+   */
+  public synchronized void resetNativeHandle(final long newNativeHandle,
+      final boolean owningNativeHandle) {
+    close();
+    setNativeHandle(newNativeHandle, owningNativeHandle);
+  }
+
+  /**
+   * Sets the handle (C++ pointer) of the underlying C++ native object
+   *
+   * @param nativeHandle The C++ pointer to the native object
+   * @param owningNativeHandle true if we own the native object
+   */
   public synchronized void setNativeHandle(final long nativeHandle,
       final boolean owningNativeHandle) {
     this.nativeHandle_ = nativeHandle;

java/src/main/java/org/rocksdb/Slice.java

@@ -14,6 +14,13 @@ package org.rocksdb;
  * values consider using {@link org.rocksdb.DirectSlice}</p>
  */
 public class Slice extends AbstractSlice<byte[]> {
+
+  /**
+   * Indicates whether we have to free the memory pointed to by the Slice
+   */
+  private volatile boolean cleared;
+  private volatile long internalBufferOffset = 0;
+
   /**
    * <p>Called from JNI to construct a new Java Slice
    * without an underlying C++ object set
@@ -27,6 +34,7 @@ public class Slice extends AbstractSlice<byte[]> {
    * Slice objects through this, they are not creating underlying C++ Slice
    * objects, and so there is nothing to free (dispose) from Java.</p>
    */
+  @SuppressWarnings("unused")
   private Slice() {
     super();
   }
@@ -62,6 +70,18 @@ public class Slice extends AbstractSlice<byte[]> {
     super(createNewSlice1(data));
   }
 
+  @Override
+  public void clear() {
+    clear0(getNativeHandle(), !cleared, internalBufferOffset);
+    cleared = true;
+  }
+
+  @Override
+  public void removePrefix(final int n) {
+    removePrefix0(getNativeHandle(), n);
+    this.internalBufferOffset += n;
+  }
+
   /**
    * <p>Deletes underlying C++ slice pointer
    * and any buffered data.</p>
@@ -74,7 +94,9 @@ public class Slice extends AbstractSlice<byte[]> {
   @Override
   protected void disposeInternal() {
     final long nativeHandle = getNativeHandle();
-    disposeInternalBuf(nativeHandle);
+    if(!cleared) {
+      disposeInternalBuf(nativeHandle, internalBufferOffset);
+    }
     super.disposeInternal(nativeHandle);
   }
 
@@ -82,5 +104,9 @@ public class Slice extends AbstractSlice<byte[]> {
   private native static long createNewSlice0(final byte[] data,
       final int length);
   private native static long createNewSlice1(final byte[] data);
-  private native void disposeInternalBuf(final long handle);
+  private native void clear0(long handle, boolean internalBuffer,
+      long internalBufferOffset);
+  private native void removePrefix0(long handle, int length);
+  private native void disposeInternalBuf(final long handle,
+      long internalBufferOffset);
 }

java/src/main/java/org/rocksdb/StringAppendOperator.java

@@ -9,9 +9,11 @@ package org.rocksdb;
  * StringAppendOperator is a merge operator that concatenates
  * two strings.
  */
-public class StringAppendOperator implements MergeOperator {
+public class StringAppendOperator extends MergeOperator {
-    @Override public long newMergeOperatorHandle() {
+    public StringAppendOperator() {
-        return newMergeOperatorHandleImpl();
+        super(newSharedStringAppendOperator());
     }
-    private native long newMergeOperatorHandleImpl();
+
+    private native static long newSharedStringAppendOperator();
+    @Override protected final native void disposeInternal(final long handle);
 }

java/src/main/java/org/rocksdb/TransactionLogIterator.java

@@ -65,7 +65,7 @@ public class TransactionLogIterator extends RocksObject {
    * by a TransactionLogIterator containing a sequence
    * number and a {@link WriteBatch} instance.</p>
    */
-  public final class BatchResult {
+  public static final class BatchResult {
     /**
      * <p>Constructor of BatchResult class.</p>
      *

java/src/main/java/org/rocksdb/WBWIRocksIterator.java

@@ -29,12 +29,11 @@ public class WBWIRocksIterator
    */
   public WriteEntry entry() {
     assert(isOwningHandle());
-    assert(entry != null);
     final long ptrs[] = entry1(nativeHandle_);
 
     entry.type = WriteType.fromId((byte)ptrs[0]);
-    entry.key.setNativeHandle(ptrs[1], true);
+    entry.key.resetNativeHandle(ptrs[1], ptrs[1] != 0);
-    entry.value.setNativeHandle(ptrs[2], ptrs[2] != 0);
+    entry.value.resetNativeHandle(ptrs[2], ptrs[2] != 0);
 
     return entry;
   }
@@ -75,6 +74,12 @@ public class WBWIRocksIterator
     }
   }
 
+  @Override
+  public void close() {
+    entry.close();
+    super.close();
+  }
+
   /**
    * Represents an entry returned by
    * {@link org.rocksdb.WBWIRocksIterator#entry()}
@@ -84,7 +89,7 @@ public class WBWIRocksIterator
    * or {@link org.rocksdb.WBWIRocksIterator.WriteType#LOG}
    * will not have a value.
    */
-  public static class WriteEntry {
+  public static class WriteEntry implements AutoCloseable {
     WriteType type = null;
     final DirectSlice key;
     final DirectSlice value;
@@ -101,7 +106,8 @@ public class WBWIRocksIterator
       value = new DirectSlice();
     }
 
-    public WriteEntry(WriteType type, DirectSlice key, DirectSlice value) {
+    public WriteEntry(final WriteType type, final DirectSlice key,
+        final DirectSlice value) {
       this.type = type;
       this.key = key;
       this.value = value;
@@ -154,7 +160,7 @@ public class WBWIRocksIterator
     }
 
     @Override
-    public boolean equals(Object other) {
+    public boolean equals(final Object other) {
       if(other == null) {
         return false;
       } else if (this == other) {
@@ -168,5 +174,11 @@ public class WBWIRocksIterator
         return false;
       }
     }
+
+    @Override
+    public void close() {
+      value.close();
+      key.close();
+    }
   }
 }

java/src/main/java/org/rocksdb/WriteBatchWithIndex.java

@@ -144,6 +144,9 @@ public class WriteBatchWithIndex extends AbstractWriteBatch {
    * @param options The database options to use
    * @param key The key to read the value for
    *
+   * @return a byte array storing the value associated with the input key if
+   *     any. null if it does not find the specified key.
+   *
    * @throws RocksDBException if the batch does not have enough data to resolve
    * Merge operations, MergeInProgress status may be returned.
    */
@@ -160,6 +163,9 @@ public class WriteBatchWithIndex extends AbstractWriteBatch {
    * @param options The database options to use
    * @param key The key to read the value for
    *
+   * @return a byte array storing the value associated with the input key if
+   *     any. null if it does not find the specified key.
+   *
    * @throws RocksDBException if the batch does not have enough data to resolve
    * Merge operations, MergeInProgress status may be returned.
    */
@@ -181,10 +187,14 @@ public class WriteBatchWithIndex extends AbstractWriteBatch {
    * (the keys in this batch do not yet belong to any snapshot and will be
    * fetched regardless).
    *
+   * @param db The Rocks database
    * @param columnFamilyHandle The column family to retrieve the value from
    * @param options The read options to use
    * @param key The key to read the value for
    *
+   * @return a byte array storing the value associated with the input key if
+   *     any. null if it does not find the specified key.
+   *
    * @throws RocksDBException if the value for the key cannot be read
    */
   public byte[] getFromBatchAndDB(final RocksDB db, final ColumnFamilyHandle columnFamilyHandle,
@@ -207,9 +217,13 @@ public class WriteBatchWithIndex extends AbstractWriteBatch {
    * (the keys in this batch do not yet belong to any snapshot and will be
    * fetched regardless).
    *
+   * @param db The Rocks database
    * @param options The read options to use
    * @param key The key to read the value for
    *
+   * @return a byte array storing the value associated with the input key if
+   *     any. null if it does not find the specified key.
+   *
    * @throws RocksDBException if the value for the key cannot be read
    */
   public byte[] getFromBatchAndDB(final RocksDB db, final ReadOptions options,

java/src/test/java/org/rocksdb/ColumnFamilyTest.java

@@ -203,8 +203,9 @@ public class ColumnFamilyTest {
 
   @Test
   public void writeBatch() throws RocksDBException {
-    try (final ColumnFamilyOptions defaultCfOptions = new ColumnFamilyOptions()
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
-        .setMergeOperator(new StringAppendOperator())) {
+         final ColumnFamilyOptions defaultCfOptions = new ColumnFamilyOptions()
+             .setMergeOperator(stringAppendOperator)) {
       final List<ColumnFamilyDescriptor> cfDescriptors = Arrays.asList(
           new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY,
               defaultCfOptions),

java/src/test/java/org/rocksdb/DBOptionsTest.java

@@ -388,25 +388,11 @@ public class DBOptionsTest {
     }
   }
 
-  @Test
-  public void rateLimiterConfig() {
-    try(final DBOptions options = new DBOptions();
-        final DBOptions anotherOptions = new DBOptions()) {
-      final RateLimiterConfig rateLimiterConfig =
-          new GenericRateLimiterConfig(1000, 100 * 1000, 1);
-      options.setRateLimiterConfig(rateLimiterConfig);
-      // Test with parameter initialization
-
-      anotherOptions.setRateLimiterConfig(
-          new GenericRateLimiterConfig(1000));
-    }
-  }
-
   @Test
   public void rateLimiter() {
     try(final DBOptions options = new DBOptions();
-        final DBOptions anotherOptions = new DBOptions()) {
+        final DBOptions anotherOptions = new DBOptions();
-      final RateLimiter rateLimiter = new RateLimiter(1000, 100 * 1000, 1);
+        final RateLimiter rateLimiter = new RateLimiter(1000, 100 * 1000, 1)) {
       options.setRateLimiter(rateLimiter);
       // Test with parameter initialization
       anotherOptions.setRateLimiter(

java/src/test/java/org/rocksdb/DirectSliceTest.java

@@ -54,7 +54,7 @@ public class DirectSliceTest {
     }
   }
 
-  @Test(expected = AssertionError.class)
+  @Test(expected = IllegalArgumentException.class)
   public void directSliceInitWithoutDirectAllocation() {
     final byte[] data = "Some text".getBytes();
     final ByteBuffer buffer = ByteBuffer.wrap(data);
@@ -63,7 +63,7 @@ public class DirectSliceTest {
     }
   }
 
-  @Test(expected = AssertionError.class)
+  @Test(expected = IllegalArgumentException.class)
   public void directSlicePrefixInitWithoutDirectAllocation() {
     final byte[] data = "Some text".getBytes();
     final ByteBuffer buffer = ByteBuffer.wrap(data);
@@ -71,4 +71,23 @@ public class DirectSliceTest {
       //no-op
     }
   }
+
+  @Test
+  public void directSliceClear() {
+    try(final DirectSlice directSlice = new DirectSlice("abc")) {
+      assertThat(directSlice.toString()).isEqualTo("abc");
+      directSlice.clear();
+      assertThat(directSlice.toString()).isEmpty();
+      directSlice.clear();  // make sure we don't double-free
+    }
+  }
+
+  @Test
+  public void directSliceRemovePrefix() {
+    try(final DirectSlice directSlice = new DirectSlice("abc")) {
+      assertThat(directSlice.toString()).isEqualTo("abc");
+      directSlice.removePrefix(1);
+      assertThat(directSlice.toString()).isEqualTo("bc");
+    }
+  }
 }

java/src/test/java/org/rocksdb/EnvOptionsTest.java

@@ -118,16 +118,16 @@ public class EnvOptionsTest {
   }
 
   @Test
-  public void rateLimiterConfig() {
+  public void rateLimiter() {
-    try (final EnvOptions envOptions = new EnvOptions()) {
+    try (final EnvOptions envOptions = new EnvOptions();
-      final RateLimiterConfig rateLimiterConfig1 =
+      final RateLimiter rateLimiter1 = new RateLimiter(1000, 100 * 1000, 1)) {
-          new GenericRateLimiterConfig(1000, 100 * 1000, 1);
+      envOptions.setRateLimiter(rateLimiter1);
-      envOptions.setRateLimiterConfig(rateLimiterConfig1);
+      assertThat(envOptions.rateLimiter()).isEqualTo(rateLimiter1);
-      assertThat(envOptions.rateLimiterConfig()).isEqualTo(rateLimiterConfig1);
+
-
+      try(final RateLimiter rateLimiter2 = new RateLimiter(1000)) {
-      final RateLimiterConfig rateLimiterConfig2 = new GenericRateLimiterConfig(1000);
+        envOptions.setRateLimiter(rateLimiter2);
-      envOptions.setRateLimiterConfig(rateLimiterConfig2);
+        assertThat(envOptions.rateLimiter()).isEqualTo(rateLimiter2);
-      assertThat(envOptions.rateLimiterConfig()).isEqualTo(rateLimiterConfig2);
+      }
     }
   }
 }

java/src/test/java/org/rocksdb/KeyMayExistTest.java

@@ -43,21 +43,21 @@ public class KeyMayExistTest {
             isEqualTo(2);
         db.put("key".getBytes(), "value".getBytes());
         // Test without column family
-        StringBuffer retValue = new StringBuffer();
+        StringBuilder retValue = new StringBuilder();
         boolean exists = db.keyMayExist("key".getBytes(), retValue);
         assertThat(exists).isTrue();
         assertThat(retValue.toString()).isEqualTo("value");
 
         // Test without column family but with readOptions
         try (final ReadOptions readOptions = new ReadOptions()) {
-          retValue = new StringBuffer();
+          retValue = new StringBuilder();
           exists = db.keyMayExist(readOptions, "key".getBytes(), retValue);
           assertThat(exists).isTrue();
           assertThat(retValue.toString()).isEqualTo("value");
         }
 
         // Test with column family
-        retValue = new StringBuffer();
+        retValue = new StringBuilder();
         exists = db.keyMayExist(columnFamilyHandleList.get(0), "key".getBytes(),
             retValue);
         assertThat(exists).isTrue();
@@ -65,7 +65,7 @@ public class KeyMayExistTest {
 
         // Test with column family and readOptions
         try (final ReadOptions readOptions = new ReadOptions()) {
-          retValue = new StringBuffer();
+          retValue = new StringBuilder();
           exists = db.keyMayExist(readOptions,
               columnFamilyHandleList.get(0), "key".getBytes(),
               retValue);

java/src/test/java/org/rocksdb/MergeTest.java

@@ -89,11 +89,10 @@ public class MergeTest {
   @Test
   public void operatorOption()
       throws InterruptedException, RocksDBException {
-    final StringAppendOperator stringAppendOperator =
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
-        new StringAppendOperator();
+         final Options opt = new Options()
-    try (final Options opt = new Options()
+            .setCreateIfMissing(true)
-        .setCreateIfMissing(true)
+            .setMergeOperator(stringAppendOperator);
-        .setMergeOperator(stringAppendOperator);
          final RocksDB db = RocksDB.open(opt,
              dbFolder.getRoot().getAbsolutePath())) {
       // Writing aa under key
@@ -112,10 +111,9 @@ public class MergeTest {
   @Test
   public void cFOperatorOption()
       throws InterruptedException, RocksDBException {
-    final StringAppendOperator stringAppendOperator =
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
-        new StringAppendOperator();
+         final ColumnFamilyOptions cfOpt1 = new ColumnFamilyOptions()
-    try (final ColumnFamilyOptions cfOpt1 = new ColumnFamilyOptions()
+             .setMergeOperator(stringAppendOperator);
-        .setMergeOperator(stringAppendOperator);
          final ColumnFamilyOptions cfOpt2 = new ColumnFamilyOptions()
              .setMergeOperator(stringAppendOperator)
     ) {
@@ -175,42 +173,43 @@ public class MergeTest {
   @Test
   public void operatorGcBehaviour()
       throws RocksDBException {
-    final StringAppendOperator stringAppendOperator
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator()) {
-        = new StringAppendOperator();
+      try (final Options opt = new Options()
-    try (final Options opt = new Options()
+              .setCreateIfMissing(true)
-        .setCreateIfMissing(true)
+              .setMergeOperator(stringAppendOperator);
-        .setMergeOperator(stringAppendOperator);
+           final RocksDB db = RocksDB.open(opt,
-         final RocksDB db = RocksDB.open(opt,
+                   dbFolder.getRoot().getAbsolutePath())) {
-             dbFolder.getRoot().getAbsolutePath())) {
+        //no-op
-      //no-op
+      }
-    }
 
-    // test reuse
-    try (final Options opt = new Options()
-        .setMergeOperator(stringAppendOperator);
-         final RocksDB db = RocksDB.open(opt,
-             dbFolder.getRoot().getAbsolutePath())) {
-      //no-op
-    }
 
-    // test param init
+      // test reuse
-    try (final Options opt = new Options()
+      try (final Options opt = new Options()
-        .setMergeOperator(new StringAppendOperator());
+              .setMergeOperator(stringAppendOperator);
-         final RocksDB db = RocksDB.open(opt,
+           final RocksDB db = RocksDB.open(opt,
-             dbFolder.getRoot().getAbsolutePath())) {
+                   dbFolder.getRoot().getAbsolutePath())) {
-      //no-op
+        //no-op
-    }
+      }
 
-    // test replace one with another merge operator instance
+      // test param init
-    try (final Options opt = new Options()
+      try (final StringAppendOperator stringAppendOperator2 = new StringAppendOperator();
-        .setMergeOperator(stringAppendOperator)) {
+           final Options opt = new Options()
-      final StringAppendOperator newStringAppendOperator
+              .setMergeOperator(stringAppendOperator2);
-          = new StringAppendOperator();
+           final RocksDB db = RocksDB.open(opt,
-      opt.setMergeOperator(newStringAppendOperator);
+                   dbFolder.getRoot().getAbsolutePath())) {
-      try (final RocksDB db = RocksDB.open(opt,
-          dbFolder.getRoot().getAbsolutePath())) {
         //no-op
       }
+
+      // test replace one with another merge operator instance
+      try (final Options opt = new Options()
+              .setMergeOperator(stringAppendOperator);
+           final StringAppendOperator newStringAppendOperator = new StringAppendOperator()) {
+        opt.setMergeOperator(newStringAppendOperator);
+        try (final RocksDB db = RocksDB.open(opt,
+                dbFolder.getRoot().getAbsolutePath())) {
+          //no-op
+        }
+      }
     }
   }
 

java/src/test/java/org/rocksdb/OptionsTest.java

@@ -697,16 +697,15 @@ public class OptionsTest {
 
   @Test
   public void compressionPerLevel() {
-    try (final ColumnFamilyOptions columnFamilyOptions =
+    try (final Options options = new Options()) {
-             new ColumnFamilyOptions()) {
+      assertThat(options.compressionPerLevel()).isEmpty();
-      assertThat(columnFamilyOptions.compressionPerLevel()).isEmpty();
       List<CompressionType> compressionTypeList =
           new ArrayList<>();
-      for (int i = 0; i < columnFamilyOptions.numLevels(); i++) {
+      for (int i = 0; i < options.numLevels(); i++) {
         compressionTypeList.add(CompressionType.NO_COMPRESSION);
       }
-      columnFamilyOptions.setCompressionPerLevel(compressionTypeList);
+      options.setCompressionPerLevel(compressionTypeList);
-      compressionTypeList = columnFamilyOptions.compressionPerLevel();
+      compressionTypeList = options.compressionPerLevel();
       for (final CompressionType compressionType : compressionTypeList) {
         assertThat(compressionType).isEqualTo(
             CompressionType.NO_COMPRESSION);
@@ -716,19 +715,18 @@ public class OptionsTest {
 
   @Test
   public void differentCompressionsPerLevel() {
-    try (final ColumnFamilyOptions columnFamilyOptions =
+    try (final Options options = new Options()) {
-             new ColumnFamilyOptions()) {
+      options.setNumLevels(3);
-      columnFamilyOptions.setNumLevels(3);
 
-      assertThat(columnFamilyOptions.compressionPerLevel()).isEmpty();
+      assertThat(options.compressionPerLevel()).isEmpty();
       List<CompressionType> compressionTypeList = new ArrayList<>();
 
       compressionTypeList.add(CompressionType.BZLIB2_COMPRESSION);
       compressionTypeList.add(CompressionType.SNAPPY_COMPRESSION);
       compressionTypeList.add(CompressionType.LZ4_COMPRESSION);
 
-      columnFamilyOptions.setCompressionPerLevel(compressionTypeList);
+      options.setCompressionPerLevel(compressionTypeList);
-      compressionTypeList = columnFamilyOptions.compressionPerLevel();
+      compressionTypeList = options.compressionPerLevel();
 
       assertThat(compressionTypeList.size()).isEqualTo(3);
       assertThat(compressionTypeList).
@@ -767,26 +765,12 @@ public class OptionsTest {
     }
   }
 
-  @Test
-  public void rateLimiterConfig() {
-    try (final Options options = new Options();
-         final Options anotherOptions = new Options()) {
-      final RateLimiterConfig rateLimiterConfig =
-          new GenericRateLimiterConfig(1000, 100 * 1000, 1);
-      options.setRateLimiterConfig(rateLimiterConfig);
-      // Test with parameter initialization
-
-      anotherOptions.setRateLimiterConfig(
-          new GenericRateLimiterConfig(1000));
-    }
-  }
-
   @Test
   public void rateLimiter() {
     try (final Options options = new Options();
-         final Options anotherOptions = new Options()) {
+         final Options anotherOptions = new Options();
-      final RateLimiter rateLimiter =
+         final RateLimiter rateLimiter =
-          new RateLimiter(1000, 100 * 1000, 1);
+             new RateLimiter(1000, 100 * 1000, 1)) {
       options.setRateLimiter(rateLimiter);
       // Test with parameter initialization
       anotherOptions.setRateLimiter(
@@ -810,7 +794,6 @@ public class OptionsTest {
     }
   }
 
-
   @Test
   public void shouldTestMemTableFactoryName()
       throws RocksDBException {

java/src/test/java/org/rocksdb/RateLimiterTest.java

@@ -0,0 +1,49 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+package org.rocksdb;
+
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class RateLimiterTest {
+
+  @ClassRule
+  public static final RocksMemoryResource rocksMemoryResource =
+      new RocksMemoryResource();
+
+  @Test
+  public void setBytesPerSecond() {
+    try(final RateLimiter rateLimiter =
+            new RateLimiter(1000, 100 * 1000, 1)) {
+      rateLimiter.setBytesPerSecond(2000);
+    }
+  }
+
+  @Test
+  public void getSingleBurstBytes() {
+    try(final RateLimiter rateLimiter =
+            new RateLimiter(1000, 100 * 1000, 1)) {
+      assertThat(rateLimiter.getSingleBurstBytes()).isEqualTo(100);
+    }
+  }
+
+  @Test
+  public void getTotalBytesThrough() {
+    try(final RateLimiter rateLimiter =
+            new RateLimiter(1000, 100 * 1000, 1)) {
+      assertThat(rateLimiter.getTotalBytesThrough()).isEqualTo(0);
+    }
+  }
+
+  @Test
+  public void getTotalRequests() {
+    try(final RateLimiter rateLimiter =
+            new RateLimiter(1000, 100 * 1000, 1)) {
+      assertThat(rateLimiter.getTotalRequests()).isEqualTo(0);
+    }
+  }
+}

java/src/test/java/org/rocksdb/RocksDBTest.java

@@ -73,8 +73,10 @@ public class RocksDBTest {
 
   @Test
   public void write() throws RocksDBException {
-    try (final Options options = new Options().setMergeOperator(
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
-        new StringAppendOperator()).setCreateIfMissing(true);
+         final Options options = new Options()
+             .setMergeOperator(stringAppendOperator)
+             .setCreateIfMissing(true);
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath());
          final WriteOptions opts = new WriteOptions()) {
@@ -182,9 +184,10 @@ public class RocksDBTest {
 
   @Test
   public void merge() throws RocksDBException {
-    try (final Options opt = new Options()
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
-        .setCreateIfMissing(true)
+         final Options opt = new Options()
-        .setMergeOperator(new StringAppendOperator());
+            .setCreateIfMissing(true)
+            .setMergeOperator(stringAppendOperator);
          final WriteOptions wOpt = new WriteOptions();
          final RocksDB db = RocksDB.open(opt,
              dbFolder.getRoot().getAbsolutePath())

java/src/test/java/org/rocksdb/SliceTest.java

@@ -32,6 +32,25 @@ public class SliceTest {
     }
   }
 
+  @Test
+  public void sliceClear() {
+    try (final Slice slice = new Slice("abc")) {
+      assertThat(slice.toString()).isEqualTo("abc");
+      slice.clear();
+      assertThat(slice.toString()).isEmpty();
+      slice.clear();  // make sure we don't double-free
+    }
+  }
+
+  @Test
+  public void sliceRemovePrefix() {
+    try (final Slice slice = new Slice("abc")) {
+      assertThat(slice.toString()).isEqualTo("abc");
+      slice.removePrefix(1);
+      assertThat(slice.toString()).isEqualTo("bc");
+    }
+  }
+
   @Test
   public void sliceEquals() {
     try (final Slice slice = new Slice("abc");

java/src/test/java/org/rocksdb/WriteBatchWithIndexTest.java

@@ -192,16 +192,16 @@ public class WriteBatchWithIndexTest {
       final ByteBuffer buffer = ByteBuffer.allocateDirect(zeroByteValue.length);
       buffer.put(zeroByteValue);
 
-      WBWIRocksIterator.WriteEntry[] expected = {
+      final WBWIRocksIterator.WriteEntry expected =
           new WBWIRocksIterator.WriteEntry(WBWIRocksIterator.WriteType.PUT,
               new DirectSlice(buffer, zeroByteValue.length),
-              new DirectSlice(buffer, zeroByteValue.length))
+              new DirectSlice(buffer, zeroByteValue.length));
-      };
 
       try (final WBWIRocksIterator it = wbwi.newIterator()) {
         it.seekToFirst();
-        assertThat(it.entry().equals(expected[0])).isTrue();
+        final WBWIRocksIterator.WriteEntry actual = it.entry();
-        assertThat(it.entry().hashCode() == expected[0].hashCode()).isTrue();
+        assertThat(actual.equals(expected)).isTrue();
+        assertThat(it.entry().hashCode() == expected.hashCode()).isTrue();
       }
     }
   }

java/src/test/java/org/rocksdb/test/RocksJunitRunner.java

@@ -31,12 +31,12 @@ public class RocksJunitRunner {
      *
      * @param system JUnitSystem
      */
-    public RocksJunitListener(JUnitSystem system) {
+    public RocksJunitListener(final JUnitSystem system) {
       super(system);
     }
 
     @Override
-    public void testStarted(Description description) {
+    public void testStarted(final Description description) {
        System.out.format("Run: %s testing now -> %s \n",
            description.getClassName(),
            description.getMethodName());
@@ -48,21 +48,23 @@ public class RocksJunitRunner {
    *
    * @param args Test classes as String names
    */
-  public static void main(String[] args){
+  public static void main(final String[] args){
-    JUnitCore runner = new JUnitCore();
+    final JUnitCore runner = new JUnitCore();
     final JUnitSystem system = new RealSystem();
     runner.addListener(new RocksJunitListener(system));
     try {
-      List<Class<?>> classes = new ArrayList<>();
+      final List<Class<?>> classes = new ArrayList<>();
-      for (String arg : args) {
+      for (final String arg : args) {
         classes.add(Class.forName(arg));
       }
-      final Result result = runner.run(classes.toArray(new Class[1]));
+      final Class[] clazzes = classes.toArray(new Class[classes.size()]);
+      final Result result = runner.run(clazzes);
       if(!result.wasSuccessful()) {
         System.exit(-1);
       }
-    } catch (ClassNotFoundException e) {
+    } catch (final ClassNotFoundException e) {
       e.printStackTrace();
+      System.exit(-2);
     }
   }
 }