test: adding java 7 check

.github/sync-repo-settings.yaml

@@ -8,6 +8,7 @@ branchProtectionRules:
     requiresCodeOwnerReviews: true
     requiresStrictStatusChecks: false
     requiredStatusCheckContexts:
+      - units (7)
       - units (8)
       - units (11)
       - windows

.github/workflows/ci-java7.yaml

@@ -0,0 +1,62 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# Github action job to test core java library features on
+# downstream client libraries before they are released.
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+name: ci-java7
+jobs:
+  units:
+    name: "units (7)"
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-java@v1
+      # setup-java v2 or higher does not have version 1.7
+      with:
+        version: 1.7
+        architecture: x64
+    - run: |
+        java -version
+        # This value is used in "-Djvm=" later
+        echo "JAVA7_HOME=${JAVA_HOME}" >> $GITHUB_ENV
+    - uses: actions/setup-java@v3
+      with:
+        java-version: 17
+        distribution: temurin
+    - name: Set up Maven
+      uses: stCarolas/setup-maven@v4.5
+      with:
+        maven-version: 3.8.8
+    - name: Build
+      shell: bash
+      run: |
+        # Leveraging surefire's jvm option, running the test on Java 7.
+        # Surefire plugin 2.22.2 is the last version for Java 7. Newer version would fail with 
+        # "UnsupportedClassVersionError: org/apache/maven/surefire/booter/ForkedBooter" error.
+
+        # Why are these modules are skipped?
+        # google-http-client-jackson2 and google-http-client-appengine do not work with Java 7
+        # any more because of Jackson and appengine library are compiled for Java 8.
+        # dailymotion-simple-cmdline-sample and google-http-client-assembly depend on
+        # google-http-client-jackson2 
+        mvn --batch-mode --show-version -ntp test \
+            --projects '!google-http-client-jackson2,!google-http-client-appengine,!samples/dailymotion-simple-cmdline-sample,!google-http-client-assembly' \
+            -Dclirr.skip=true -Denforcer.skip=true -Dmaven.javadoc.skip=true \
+            -Dgcloud.download.skip=true -T 1C \
+            -Dproject.surefire.version=2.22.2 \
+            -Djvm=${JAVA7_HOME}/bin/java

README.md

@@ -18,6 +18,8 @@ content. The JSON and XML libraries are also fully pluggable, and they include s
 The library supports the following Java environments:
 
 - Java 7 or higher
+  - The google-http-client-jackson2 and google-http-client-appengine modules require Java 8 or
+    higher due to their dependencies.
 - Android 4.4 (Kit Kat)
 - GoogleAppEngine Google App Engine
 

pom.xml

@@ -326,7 +326,7 @@
         </plugin>
         <plugin>
           <artifactId>maven-surefire-plugin</artifactId>
-          <version>3.0.0-M7</version>
+          <version>${project.surefire.version}</version>
           <configuration>
             <argLine>-Xmx1024m</argLine>
             <reportNameSuffix>sponge_log</reportNameSuffix>
@@ -581,6 +581,7 @@
     <project.httpcore.version>4.4.16</project.httpcore.version>
     <project.opencensus.version>0.31.1</project.opencensus.version>
     <project.root-directory>..</project.root-directory>
+    <project.surefire.version>3.0.0-M7</project.surefire.version>
     <deploy.autorelease>false</deploy.autorelease>
   </properties>