chore: add GitLab CI pipeline with build, container registry push, and deploy stages

.gitlab-ci.yml

@@ -0,0 +1,157 @@
+stages:
+  - package
+  - build-image
+  - push
+  - deploy
+
+variables:
+  # ---------- Gradle ----------
+  GRADLE_IMAGE: gradle:8.14.4-jdk21
+  GRADLE_USER_HOME: ${CI_PROJECT_DIR}/.gradle
+
+  # ---------- Docker ----------
+  DOCKER_IMAGE: docker:27.5.1
+  DOCKER_SERVICE: docker:27.5.1-dind
+  DOCKER_HOST: tcp://docker:2375
+  DOCKER_TLS_CERTDIR: ""
+
+  # ---------- Application ----------
+  APP_NAME: delta-force-guide-server
+
+  # ---------- Image tags ----------
+  IMAGE_TAG: ${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHORT_SHA}
+  LATEST_TAG: ${CI_REGISTRY_IMAGE}:latest
+
+  # ---------- CI Dockerfile ----------
+  CI_DOCKERFILE: Dockerfile.ci
+
+cache:
+  key: ${CI_COMMIT_REF_SLUG}
+  paths:
+    - .gradle/wrapper
+    - .gradle/caches
+  policy: pull-push
+
+# ====================================================================
+# Reusable template for Docker jobs
+# ====================================================================
+.docker:
+  image: ${DOCKER_IMAGE}
+  services:
+    - name: ${DOCKER_SERVICE}
+      command: ["--tls=false"]
+  variables:
+    DOCKER_HOST: tcp://docker:2375
+    DOCKER_TLS_CERTDIR: ""
+
+# Trigger the pipeline for MRs, the default branch, and tags
+workflow:
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
+    - if: '$CI_COMMIT_TAG'
+
+# ====================================================================
+# Stage 1 — Package: build the JAR with Gradle
+# ====================================================================
+package:
+  stage: package
+  image: ${GRADLE_IMAGE}
+  script:
+    - ./gradlew build
+  artifacts:
+    name: "${CI_JOB_NAME}-${CI_COMMIT_SHORT_SHA}"
+    paths:
+      - build/libs/*.jar
+    expire_in: 1 hour
+
+# ====================================================================
+# Stage 2 — Build Docker image using the pre-built JAR artifact
+# ====================================================================
+build-image:
+  stage: build-image
+  extends: .docker
+  script:
+    # Resolve the actual JAR path
+    - JAR_FILE=$(ls build/libs/delta-force-guide-server-*.jar | head -1)
+    - echo "Packaging JAR: ${JAR_FILE}"
+
+    # Build image with the CI-specific single-stage Dockerfile
+    - |
+      docker build \
+        --build-arg JAR_FILE="${JAR_FILE}" \
+        -f ${CI_DOCKERFILE} \
+        -t ${IMAGE_TAG} \
+        -t ${LATEST_TAG} \
+        .
+
+    # Save the image as a CI artefact for the next stage
+    - docker save ${IMAGE_TAG} ${LATEST_TAG} > image.tar
+  artifacts:
+    paths:
+      - image.tar
+    expire_in: 1 hour
+  needs:
+    - package
+
+# ====================================================================
+# Stage 3 — Push image to GitLab Container Registry
+# ====================================================================
+push:
+  stage: push
+  extends: .docker
+  script:
+    - docker load < image.tar
+    - docker login -u ${CI_REGISTRY_USER} -p ${CI_REGISTRY_PASSWORD} ${CI_REGISTRY}
+    - docker push ${IMAGE_TAG}
+    - docker push ${LATEST_TAG}
+  needs:
+    - build-image
+  rules:
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
+    - if: '$CI_COMMIT_TAG'
+
+# ====================================================================
+# Stage 4 — Deploy on the target server via SSH
+# ====================================================================
+deploy:
+  stage: deploy
+  image: alpine:latest
+  before_script:
+    - apk add --no-cache openssh-client
+    - eval "$(ssh-agent -s)"
+    - echo "${DEPLOY_SSH_PRIVATE_KEY}" | tr -d '\r' | ssh-add -
+    - mkdir -p ~/.ssh
+    - chmod 700 ~/.ssh
+  script:
+    - |
+      ssh -o StrictHostKeyChecking=no ${DEPLOY_USER}@${DEPLOY_HOST} "
+        set -e
+
+        echo '=== Pulling image ==='
+        echo ${CI_REGISTRY_PASSWORD} | docker login -u ${CI_REGISTRY_USER} --password-stdin ${CI_REGISTRY}
+        docker pull ${IMAGE_TAG}
+
+        echo '=== Stopping old container ==='
+        docker stop ${APP_NAME} || true
+        docker rm ${APP_NAME} || true
+
+        echo '=== Starting new container ==='
+        docker run -d \
+          --name ${APP_NAME} \
+          --restart unless-stopped \
+          -p ${DEPLOY_PORT:-8080}:8080 \
+          ${IMAGE_TAG}
+
+        echo '=== Cleaning up old images ==='
+        docker image prune -f
+
+        echo '=== Deployment complete ==='
+      "
+  needs:
+    - push
+  environment:
+    name: production
+    url: http://${DEPLOY_HOST}:${DEPLOY_PORT:-8080}
+  rules:
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'

Dockerfile.ci

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+FROM amazoncorretto:21-alpine
+WORKDIR /app
+
+ARG JAR_FILE
+COPY ${JAR_FILE} app.jar
+
+ENTRYPOINT ["java", "-jar", "app.jar"]