Github-Action: gradle instead of maven.

.github/workflows/gradle.yml

@@ -0,0 +1,31 @@
+# This workflow will build a Java project with Gradle
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Java CI with Gradle
+
+on:
+  push:
+    branches: [ develop ]
+    paths-ignore:
+      - 'site/**'
+  pull_request:
+    branches: [ develop ]
+    paths-ignore:
+      - 'site/**'
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 17
+        uses: actions/setup-java@v2
+        with:
+          java-version: '17'
+          distribution: 'adopt'
+      - name: Grant execute permission for Gradle wrapper
+        run: chmod +x gradlew
+      - name: Build with Gradle
+        run: ./gradlew build