Make sure to use the correct Java classloader for loading the RocksDB

Native Library

java/org/rocksdb/NativeLibraryLoader.java

@@ -11,11 +11,35 @@ import org.rocksdb.util.Environment;
  * The shared library is extracted to a temp folder and loaded from there.
  */
 public class NativeLibraryLoader {
+  //singleton
+  private static final NativeLibraryLoader instance = new NativeLibraryLoader();
+
   private static final String sharedLibraryName = Environment.getJniLibraryName("rocksdb");
   private static final String tempFilePrefix = "librocksdbjni";
   private static final String tempFileSuffix = "." + Environment.getJniLibraryExtension();
 
-  public static void loadLibraryFromJar(final String tmpDir)
+  /**
+   * Get a reference to the NativeLibraryLoader
+   *
+   * @return The NativeLibraryLoader
+   */
+  public static NativeLibraryLoader getInstance() {
+    return instance;
+  }
+
+  /**
+   * Attempts to extract the native RocksDB library
+   * from the classpath and load it
+   *
+   * @param tmpDir A temporary directory to use
+   *   to copy the native library to. If null,
+   *   or the empty string, we rely on Java's
+   *   {@see java.io.File#createTempFile(String, String) }
+   *   function to provide a temporary location.
+   *   The temporary file will be registered for deletion
+   *   on exit.
+   */
+  public void loadLibraryFromJar(final String tmpDir)
       throws IOException {
     final File temp;
     if(tmpDir == null || tmpDir.equals("")) {
@@ -30,8 +54,8 @@ public class NativeLibraryLoader {
       temp.deleteOnExit();
     }
 
-    // attempt to copy the library from the JAR to the temp destination
+    // attempt to copy the library from the Jar file to the temp destination
-    try(final InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream(sharedLibraryName)) {
+    try(final InputStream is = getClass().getClassLoader().getResourceAsStream(sharedLibraryName)) {
       if (is == null) {
         throw new RuntimeException(sharedLibraryName + " was not found inside JAR.");
       } else {

java/org/rocksdb/RocksDB.java

@@ -44,7 +44,7 @@ public class RocksDB extends RocksObject {
     }
     try
     {
-      NativeLibraryLoader.loadLibraryFromJar(tmpDir);
+      NativeLibraryLoader.getInstance().loadLibraryFromJar(tmpDir);
     }
     catch (IOException e)
     {