GitHub Actions and Maven

Since I maintain some OpenSource projects its important to know the projects state. Those projects are using Maven. So a simple local build and test is an easy task. However, the state should be visible right from the projects main page. So at the moment I use TravisCI to build my projects and from it I derive some nice build - badges, to show the state and the build result. I am no TravisCI expert, I just use it with this simple script:

language: java
jdk:
  - openjdk8
  - openjdk11

after_success:
  - mvn clean

This builds my maven project with Java 8 and Java 11 and after a success it cleans it all up again.

So I have heard of GitHub Actions and wanted to give it a try. Since GitHub is a nice place I would prefer, to keep all stuff on one place. The target is to do the same like with this TravisCI script.

The simple start

GitHub provides a very simple way to start. You could follow it here for maven: here.

Or just use the Action menu of your GitHub repository and click Setup this workflow for Java with Maven. This will generate this workflow script for you:

# This workflow will build a Java project with Maven
# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven

name: Java CI with Maven

on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

jobs:
  build:

    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v2
    - name: Set up JDK 1.8
      uses: actions/setup-java@v1
      with:
        java-version: 1.8
    - name: Build with Maven
      run: mvn -B package --file pom.xml

Note: All those configured workflows of your projects are stored within a directory .github/workflows and are therefore part of your repository.

So at first a simple explanation to what this does. So the basic structure of an action or workflow. All this is a YAML file.

It starts simply with some naming stuff:

name: Java CI with Maven

Then we come to the event section, which defines, on which events this action should be started. Here it starts on push and pull events on your master branch.

on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

And last but not least, the jobs itself. What should be done running this action. Here the steps will run on a linux (ubuntu-latest). So it will checkout the latest sources, setup a JDK 1.8 and runs a maven -B package –file pom.xml command.

jobs:
  build:

    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v2
    - name: Set up JDK 1.8
      uses: actions/setup-java@v1
      with:
        java-version: 1.8
    - name: Build with Maven
      run: mvn -B package --file pom.xml

So thats it.

Under actions you will see the list of runs for your action(s). From here ( … button) you can create the needed build status badge.

Building on multiple JDKs

Since I want to have JDK 11 and above ready projects, this workflow needs to be configured to run the build on multiple JDKs.

To get this kind of for each loop, I use the matrix strategy of GitHub Actions. You provide a list of values, that the workflow iterates through or even processes in parallel.

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix: 
        java: [8, 11]
    name: Java ${{ matrix.java }} building ... 
    steps:
    - uses: actions/checkout@v2
    - name: Set up Java ${{ matrix.java }} 
      uses: actions/setup-java@v1
      with:
        java-version: ${{ matrix.java }} 
    - name: Build with Maven
      run: mvn -B package --file pom.xml

You see this new section strategy. There are our Java versions definied: 8 and 11. Within the steps we can now use the actual value using this kind of macro ${{ matrix.java }}.

Conclusion

So that was easy. Its a bit more complex than TravisCI build definition, but I kind of like it. Additionally there are dozens of ready to use workflows available for deployment, publishing, building, maintaining your repository.

• Greetings: greets first time contributors for a project
• Stale: labels stale issues and pull requests
• …

For public projects you have 2,000 Actions minutes/month free. For normal sizes this is sufficient, but you can purchase more.