move build step to Dockerfile

.github/actions/docker-build-or-tag/action.yml

@@ -46,23 +46,14 @@ runs:
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v3
 
-    - name: Set up JDK 17
-      uses: actions/setup-java@v3
-      with:
-        java-version: '17'
-        distribution: 'corretto'
-        cache: maven
-
-    - name: Build with Maven
-      run: mvn clean package -DskipTests
-      shell: bash
-
     - name: Build and push
       uses: docker/build-push-action@v6
       with:
         push: true
         platforms: linux/amd64,linux/arm64
         context: ${{ inputs.dockerfile-dir }}
+        cache-from: type=gha
+        cache-to: type=gha,mode=max
         tags: |
           ghcr.io/januschung/${{ inputs.image-name }}:${{ env.COMMIT_SHA }}
           ghcr.io/januschung/${{ inputs.image-name }}:latest

Dockerfile

@@ -1,4 +1,16 @@
+# Stage 1: build the application
+FROM maven:3.9.4-eclipse-temurin-17 AS build
+WORKDIR /workspace
+COPY pom.xml ./
+COPY .mvn .mvn
+# use BuildKit cache for Maven repo
+RUN --mount=type=cache,target=/root/.m2 mvn -B -DskipTests dependency:go-offline
+COPY src ./src
+RUN --mount=type=cache,target=/root/.m2 mvn -B -DskipTests package
+
+# Stage 2: runtime image
 FROM amazoncorretto:17-alpine3.21
-COPY target/*.jar app.jar
+WORKDIR /app
+COPY --from=build /workspace/target/*.jar app.jar
 EXPOSE 8080
 ENTRYPOINT ["java", "-jar", "/app.jar"]