About

Generate Dockerfile and docker-bake.hcl for docker/bake-action to build Spring Boot Docker Image

Explaination

This action generates a Dockerfile and a docker-bake.hcl for docker/bake-action to build a Spring Boot Docker image. And the structure of the container image is as follows:

Stage 1:

1. Prepare working directory for building Docker Image
2. Copy necessary files to .spring-boot-bake in the working directory

Stage 2:

1. Extract JAR file from the Spring Boot fat JAR archive to /spring-boot-archive
2. Generate /docker-entrypoint.sh script
3. Configure JVM options via ARG and ENV for the Docker image
4. Copy Spring Boot layers from /spring-boot-archive to /spring-boot

Note
Starting from Spring Boot 2.4, layering is enabled by default.
If you are using any version lower than 2.4, layering feature must be explicitly enabled.

Usage

This action use a pre-defined Dockerfile and docker-bake.hcl to generate a metatadata for building a Spring Boot Docker image.

There are many different ways to build a Spring Boot Docker image. This action is just one of them. You can find more information about Spring Boot Docker image in the Spring Boot Docker guide.

Feel free to explore other methods that fit your needs.

Bake definition

This action also handles a bake definition file that can be used with the Docker Bake action. You just have to declare an empty target named spring-boot-bake and inherit from it.

Note: You don't need to define dockerfile and context in the bake definition file. They are automatically set by the action.

// docker-bake.hcl
target "gradle-metadata-action" {}

target "spring-boot-bake" {
  inherits = ["gradle-metadata-action"]
}

target "default" {
  inherits = ["spring-boot-bake"]
  platforms = [
    "linux/amd64",
    "linux/arm/v6",
    "linux/arm/v7",
    "linux/arm64",
    "linux/386"
  ]
}

Customize the image:

To customize the final image or to provide you own Dockerfile. Please do following:

// docker-bake.hcl
target "gradle-metadata-action" {}

target "spring-boot-bake" {
  inherits = ["gradle-metadata-action"]
}

target "default" {
  contexts = {
    "spring-boot-bake" = "target:spring-boot-bake"
  }
  platforms = [
    "linux/amd64",
    "linux/arm/v6",
    "linux/arm/v7",
    "linux/arm64",
    "linux/386"
  ]
}

And in your Dockerfile, use spring-boot-bake as your base image.

FROM spring-boot-bake

# Add your custom Dockerfile here

You can read more here "Using a result of one target as a base image in another target".

Change the WORKDIR:

You can change the WORKDIR by setting the SPRING_BOOT_BAKE_APPDIR argument.

target "spring-boot-bake" {
  inherits = ["gradle-metadata-action"]
  args = {
    SPRING_BOOT_BAKE_APPDIR = "/app"
  }
}

GitHub Workflow

The dockerbakery/gradle-metadata-action is required to use this action.

name: ci

on:
  push:
    branches:
      - 'main'
    tags:
      - 'v*'
  pull_request:
    branches:
      - 'main'

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2

      - name: Docker meta
        id: meta
        uses: docker/metadata-action@v4
        with:
          images: |
            name/app
          tags: |
            type=ref,event=branch
            type=ref,event=pr
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
            type=sha

      - name: Gradle meta
        id: gradle-meta
        uses: dockerbakery/gradle-metadata-action@v2

      - name: Spring Boot Bake
        id: spring-bake
        uses: spring-boot-actions/spring-boot-bake@v1

      - uses: docker/bake-action@v2
        with:
          files: |
            ./docker-bake.hcl
            ${{ steps.spring-bake.outputs.bake-file }}
            ${{ steps.gradle-meta.outputs.bake-file }}
          targets: build

Inputs

Following inputs can be used as step.with keys

Name	Type	Description
base-image	String	The base image to use for the Docker image (default "eclipse-temurin:11-jre-alpine").

Outputs

Output of docker buildx bake -f spring-boot-bake.hcl --print spring-boot-bake command.

{
  "group": {
    "default": {
      "targets": [
        "spring-boot-bake"
      ]
    }
  },
  "target": {
    "spring-boot-bake": {
      "dockerfile": "${SPRING_BOOT_BAKE_PATH}/Dockerfile",
      "args": {
        "SPRING_BOOT_BAKE_PATH": "${SPRING_BOOT_BAKE_PATH}",
        "SPRING_BOOT_BAKE_BASE_IMAGE": "eclipse-temurin:17-jre-alpine",
      }
    }
  }
}

Resources

• GitHub Action Environment variables
• Workflow commands for GitHub Actions
• Bake File Definitions
• Spring Boot Docker