Building and testing Java with Maven

Introduction

This guide shows you how to create a workflow that performs continuous integration (CI) for your Java project using the Maven software project management tool. The workflow you create will allow you to see when commits to a pull request cause build or test failures against your default branch; this approach can help ensure that your code is always healthy. You can extend your CI workflow to cache files and upload artifacts from a workflow run.

GitHub-hosted runners have a tools cache with pre-installed software, which includes Java Development Kits (JDKs) and Maven. For a list of software and the pre-installed versions for JDK and Maven, see "Specifications for GitHub-hosted runners".

Prerequisites

You should be familiar with YAML and the syntax for GitHub Actions. For more information, see:

• "Workflow syntax for GitHub Actions"
• "Learn GitHub Actions"

We recommend that you have a basic understanding of Java and the Maven framework. For more information, see the Maven Getting Started Guide in the Maven documentation.

Using the Maven starter workflow

GitHub provides a Maven starter workflow that will work for most Maven-based Java projects. For more information, see the Maven starter workflow.

To get started quickly, you can choose the preconfigured Maven starter workflow when you create a new workflow. For more information, see the "GitHub Actions quickstart."

You can also add this workflow manually by creating a new file in the .github/workflows directory of your repository.

name: Java CI

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2
      - name: Set up JDK 11
        uses: actions/setup-java@v2
        with:
          java-version: '11'
          distribution: 'adopt'
      - name: Build with Maven
        run: mvn --batch-mode --update-snapshots verify

This workflow performs the following steps:

1. The checkout step downloads a copy of your repository on the runner.
2. The setup-java step configures the Java 11 JDK by Adoptium.
3. The "Build with Maven" step runs the Maven package target in non-interactive mode to ensure that your code builds, tests pass, and a package can be created.

The default starter workflows are excellent starting points when creating your build and test workflow, and you can customize the starter workflow to suit your project’s needs.

Running on a different operating system

The starter workflow configures jobs to run on Linux, using the GitHub-hosted ubuntu-latest runners. You can change the runs-on key to run your jobs on a different operating system. For example, you can use the GitHub-hosted Windows runners.

runs-on: windows-latest

Or, you can run on the GitHub-hosted macOS runners.

runs-on: macos-latest

You can also run jobs in Docker containers, or you can provide a self-hosted runner that runs on your own infrastructure. For more information, see "Workflow syntax for GitHub Actions."

Specifying the JVM version and architecture

The starter workflow sets up the PATH to contain OpenJDK 8 for the x64 platform. If you want to use a different version of Java, or target a different architecture (x64 or x86), you can use the setup-java action to choose a different Java runtime environment.

For example, to use version 11 of the JDK provided by Adoptium for the x64 platform, you can use the setup-java action and configure the java-version, distribution and architecture parameters to '11', 'adopt' and x64.

steps:
  - uses: actions/checkout@v2
  - name: Set up JDK 11 for x64
    uses: actions/setup-java@v2
    with:
      java-version: '11'
      distribution: 'adopt'
      architecture: x64

For more information, see the setup-java action.

Building and testing your code

You can use the same commands that you use locally to build and test your code.

The starter workflow will run the package target by default. In the default Maven configuration, this command will download dependencies, build classes, run tests, and package classes into their distributable format, for example, a JAR file.

If you use different commands to build your project, or you want to use a different target, you can specify those. For example, you may want to run the verify target that's configured in a pom-ci.xml file.

steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-java@v2
    with:
      java-version: '11'
      distribution: 'adopt'
  - name: Run the Maven verify phase
    run: mvn --batch-mode --update-snapshots verify

Caching dependencies

When using GitHub-hosted runners, you can cache your dependencies to speed up your workflow runs. After a successful run, your local Maven repository will be stored on GitHub Actions infrastructure. In future workflow runs, the cache will be restored so that dependencies don't need to be downloaded from remote Maven repositories. You can cache dependencies simply using the setup-java action or can use cache action for custom and more advanced configuration.

steps:
  - uses: actions/checkout@v2
  - name: Set up JDK 11
    uses: actions/setup-java@v2
    with:
      java-version: '11'
      distribution: 'adopt'
      cache: maven
  - name: Build with Maven
    run: mvn --batch-mode --update-snapshots verify

This workflow will save the contents of your local Maven repository, located in the .m2 directory of the runner's home directory. The cache key will be the hashed contents of pom.xml, so changes to pom.xml will invalidate the cache.

Packaging workflow data as artifacts

After your build has succeeded and your tests have passed, you may want to upload the resulting Java packages as a build artifact. This will store the built packages as part of the workflow run, and allow you to download them. Artifacts can help you test and debug pull requests in your local environment before they're merged. For more information, see "Persisting workflow data using artifacts."

Maven will usually create output files like JARs, EARs, or WARs in the target directory. To upload those as artifacts, you can copy them into a new directory that contains artifacts to upload. For example, you can create a directory called staging. Then you can upload the contents of that directory using the upload-artifact action.

steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-java@v2
    with:
      java-version: '11'
      distribution: 'adopt'
  - run: mvn --batch-mode --update-snapshots verify
  - run: mkdir staging && cp target/*.jar staging
  - uses: actions/upload-artifact@v3
    with:
      name: Package
      path: staging