test: use Java 17 to produce Java 8-compatible bytecode (#1681)

* test: java 8 when running Java 8 test

* Use Java 17 to produce Java 8-compatible bytecode

Author: suztomo

.github/workflows/ci.yaml

@@ -65,30 +65,19 @@ jobs:
       - run: echo "JAVA8_HOME=${JAVA_HOME}" >> $GITHUB_ENV
       - uses: actions/setup-java@v3
         with:
-          java-version: 11
+          java-version: 17
           distribution: temurin
-      - run: echo "JAVA11_HOME=${JAVA_HOME}" >> $GITHUB_ENV
-      - name: Compile with Java 11
+      - name: Compile with Java 17 and run tests with Java 8
         shell: bash
         run: |
           set -x
           export JAVA_HOME=$JAVA11_HOME
           export PATH=${JAVA_HOME}/bin:$PATH
-          # Why not compile? It's because the process needs to package jar so
-          # that gapic-generator-java module can use testlib modules of gax.
+          # Maven surefire plugin lets us to specify the JVM when running tests via
+          # the "jvm" system property.
           mvn verify --batch-mode --no-transfer-progress -Dcheckstyle.skip \
-              -DskipTests -Dfmt.skip
-      - name: Run test with Java 8 for all modules except gapic-generator-java
-        shell: bash
-        run: |
-          set -x
-          export JAVA_HOME=$JAVA8_HOME
-          export PATH=${JAVA_HOME}/bin:$PATH
-          # useIncrementalCompilation=false to avoid recompiling classes
-          # generated by Java 11 compiler above.
-          mvn -B -ntp test  --projects '!gapic-generator-java' \
-              -Dcheckstyle.skip -Dmaven.compiler.useIncrementalCompilation=false \
-              -Dfmt.skip
+              -Dfmt.skip \
+              -Djvm="${JAVA8_HOME}/bin/java"
 
   build-java8-gapic-generator-java:
     name: "build(8) for gapic-generator-java"

.kokoro/release/common.cfg

@@ -9,7 +9,7 @@ build_file: "gapic-generator-java/.kokoro/trampoline.sh"
 # Configure the docker image for kokoro-trampoline.
 env_vars: {
   key: "TRAMPOLINE_IMAGE"
-  value: "gcr.io/cloud-devrel-kokoro-resources/java11"
+  value: "gcr.io/cloud-devrel-kokoro-resources/java17"
 }
 
 before_action {