Force Java version on Travis CI (#6512)

Summary:
In the `.travis.yml` file the `jdk: openjdk7` element is ignored when `language: cpp`. So whatever version of the JDK that was installed in the Travis container was used - typically JDK 11.

To ensure our RocksJava builds are working, we now instead install and use OpenJDK 8. Ideally we would use OpenJDK 7, as RocksJava supports Java 7, but many of the newer Travis containers don't support Java 7, so Java 8 is the next best thing.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6512

Differential Revision: D20388296

Pulled By: pdillinger

fbshipit-source-id: 8bbe6b59b70cfab7fe81ff63867d907fefdd2df1

.travis.yml

@@ -10,8 +10,6 @@ compiler:
   - clang
   - gcc
 osx_image: xcode9.4
-jdk:
-  - openjdk7
 cache:
   - ccache
 
@@ -77,11 +75,6 @@ matrix:
   - os: linux
     compiler: clang
 
-before_install:
-  - if [[ "${JOB_NAME}" == java_test  || "${JOB_NAME}" == cmake* ]] && [ "$(uname -m)" == ppc64le ]; then
-     sudo apt-get -y install openjdk-8-jdk && export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-ppc64el;
-   fi
-
 install:
   - if [ "${TRAVIS_OS_NAME}" == osx ]; then
       PATH=$PATH:/usr/local/opt/ccache/libexec;
@@ -98,8 +91,21 @@ install:
       TAR_OPT="--strip-components=1 -xj";
       mkdir cmake-dist && curl --silent --fail --show-error --location "${CMAKE_DIST_URL}" | tar -C cmake-dist ${TAR_OPT} && export PATH=$PWD/cmake-dist/bin:$PATH;
     fi
-  - if [[ "${JOB_NAME}" == java_test || "${JOB_NAME}" == cmake* ]]; then
+  - |
-      java -version && echo "JAVA_HOME=${JAVA_HOME}";
+    if [[ "${JOB_NAME}" == java_test || "${JOB_NAME}" == cmake* ]]; then
+      # Ensure JDK 8
+      if [ "${TRAVIS_OS_NAME}" == osx ]; then
+        brew tap AdoptOpenJDK/openjdk
+        brew cask install adoptopenjdk8
+        export JAVA_HOME=$(/usr/libexec/java_home)
+      else
+        sudo apt-get install -y openjdk-8-jdk
+        export PATH=/usr/lib/jvm/java-8-openjdk-$(dpkg --print-architecture)/bin:$PATH
+        export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-$(dpkg --print-architecture)
+      fi
+      echo "JAVA_HOME=${JAVA_HOME}"
+      which java && java -version
+      which javac && javac -version
     fi
 
 before_script:

Makefile

@@ -207,6 +207,7 @@ AM_LINK = $(AM_V_CCLD)$(CXX) $^ $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS
 dummy := $(shell (export ROCKSDB_ROOT="$(CURDIR)"; export PORTABLE="$(PORTABLE)"; "$(CURDIR)/build_tools/build_detect_platform" "$(CURDIR)/make_config.mk"))
 # this file is generated by the previous line to set build flags and sources
 include make_config.mk
+export JAVAC_ARGS
 CLEAN_FILES += make_config.mk
 
 missing_make_config_paths := $(shell				\

build_tools/build_detect_platform

@@ -9,6 +9,7 @@
 #   PLATFORM_LDFLAGS            Linker flags
 #   JAVA_LDFLAGS                Linker flags for RocksDBJava
 #   JAVA_STATIC_LDFLAGS         Linker flags for RocksDBJava static build
+#   JAVAC_ARGS                  Arguments for javac
 #   PLATFORM_SHARED_EXT         Extension for shared libraries
 #   PLATFORM_SHARED_LDFLAGS     Flags for building shared library
 #   PLATFORM_SHARED_CFLAGS      Flags for compiling objects for shared library
@@ -239,6 +240,7 @@ esac
 PLATFORM_CXXFLAGS="$PLATFORM_CXXFLAGS ${CXXFLAGS}"
 JAVA_LDFLAGS="$PLATFORM_LDFLAGS"
 JAVA_STATIC_LDFLAGS="$PLATFORM_LDFLAGS"
+JAVAC_ARGS="-source 7"
 
 if [ "$CROSS_COMPILE" = "true" -o "$FBCODE_BUILD" = "true" ]; then
     # Cross-compiling; do not try any compilation tests.
@@ -710,6 +712,7 @@ echo "PLATFORM=$PLATFORM" >> "$OUTPUT"
 echo "PLATFORM_LDFLAGS=$PLATFORM_LDFLAGS" >> "$OUTPUT"
 echo "JAVA_LDFLAGS=$JAVA_LDFLAGS" >> "$OUTPUT"
 echo "JAVA_STATIC_LDFLAGS=$JAVA_STATIC_LDFLAGS" >> "$OUTPUT"
+echo "JAVAC_ARGS=$JAVAC_ARGS" >> "$OUTPUT"
 echo "VALGRIND_VER=$VALGRIND_VER" >> "$OUTPUT"
 echo "PLATFORM_CCFLAGS=$PLATFORM_CCFLAGS" >> "$OUTPUT"
 echo "PLATFORM_CXXFLAGS=$PLATFORM_CXXFLAGS" >> "$OUTPUT"

java/CMakeLists.txt

@@ -4,6 +4,8 @@ if(${CMAKE_VERSION} VERSION_LESS "3.11.4")
     message("Please consider switching to CMake 3.11.4 or newer")
 endif()
 
+set(CMAKE_JAVA_COMPILE_FLAGS -source 7)
+
 set(JNI_NATIVE_SOURCES
         rocksjni/backupablejni.cc
         rocksjni/backupenginejni.cc

java/Makefile

@@ -207,14 +207,14 @@ 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? =
+JAVA_ARGS ?=
 
-JAVAC_ARGS? =
+JAVAC_ARGS ?=
 
 # When debugging add -Xcheck:jni to the java args
 ifneq ($(DEBUG_LEVEL),0)
-	JAVA_ARGS = -ea -Xcheck:jni
+	JAVA_ARGS += -ea -Xcheck:jni
-	JAVAC_ARGS = -Xlint:deprecation -Xlint:unchecked
+	JAVAC_ARGS += -Xlint:deprecation -Xlint:unchecked
 endif
 
 # This is a URL for artifacts from a "fake" release on pdillinger's fork,