change Dockerfile to build .war and add simple build docker workflow

.github/workflows/build-docker.yml

@@ -0,0 +1,24 @@
+name: Continuous Integration
+
+on: [push, pull_request]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Docker build
+        uses: mr-smithers-excellent/docker-build-push@v5
+        id: build
+        with:
+          image: ${{ env.IMAGENAME }}
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}

java/Dockerfile

@@ -1,12 +1,16 @@
+FROM gradle:jdk17-jammy as builder
+
+WORKDIR /build
+COPY . ./
+RUN gradle wrapper --gradle-version 8.1.1
+RUN ./gradlew build -x test
+
+##########################################################################
 # Use official Tomcat base image
 FROM tomcat:jre17
 
 # Copy WAR file
-COPY app/build/libs/vss-1.0.war /usr/local/tomcat/webapps/vss.war
-
-ENV vss.jdbc.url="jdbc:postgresql://postgres:5432/postgres"
-ENV vss.jdbc.username=postgres
-ENV vss.jdbc.password=YOU_MUST_CHANGE_THIS_PASSWORD
+COPY --from=builder /build/app/build/libs/vss-1.0.war /usr/local/tomcat/webapps/vss.war
 
 EXPOSE 8080
 CMD ["catalina.sh", "run"]