ci: build inside a builder container (#84)

.github/workflows/ci.yml

@@ -10,12 +10,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-java@v3
-        with:
-          java-version: '17'
-          distribution: 'temurin'
-          cache: maven
-      - run: mvn --batch-mode --update-snapshots verify
       - uses: docker/setup-qemu-action@v3
       - uses: docker/setup-buildx-action@v3
       - uses: docker/build-push-action@v5

.github/workflows/main.yml

@@ -21,12 +21,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-java@v3
-        with:
-          java-version: '17'
-          distribution: 'temurin'
-          cache: maven
-      - run: mvn --batch-mode --update-snapshots verify
       - uses: docker/setup-qemu-action@v3
       - uses: docker/setup-buildx-action@v3
       - uses: docker/metadata-action@v5

Dockerfile

@@ -1,5 +1,12 @@
+FROM maven:3-eclipse-temurin-17 AS builder
+WORKDIR /workspace
+COPY pom.xml pom.xml
+RUN mvn dependency:resolve
+COPY src/ src/
+RUN mvn --batch-mode verify
+
 FROM eclipse-temurin:17.0.8_7-jre-alpine
 WORKDIR /app
-COPY target/k3a-lag-exporter-jar-with-dependencies.jar ./k3a-lag-exporter.jar
+COPY --from=builder /workspace/target/k3a-lag-exporter-jar-with-dependencies.jar ./k3a-lag-exporter.jar
 
 ENTRYPOINT ["java", "-Dconfig.file=k3a-lag-exporter.conf", "-jar", "k3a-lag-exporter.jar"]