Building and testing Java with Gradle

You can create a continuous integration (CI) workflow in GitHub Actions to build and test your Java project with Gradle.

GitHub Actions is available with GitHub Free, GitHub Pro, GitHub Free for organizations, GitHub Team, GitHub Enterprise Cloud, GitHub Enterprise Server, and GitHub One. GitHub Actions is not available for private repositories owned by accounts using legacy per-repository plans. For more information, see "GitHub's products."

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Introduction

This guide shows you how to create a workflow that performs continuous integration (CI) for your Java project using the Gradle build system. 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 Gradle. For a list of software and the pre-installed versions for JDK and Gradle, see "Specifications for GitHub-hosted runners".

Prerequisites

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

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

Starting with a Gradle workflow template

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

To get started quickly, you can choose the preconfigured Gradle template 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 1.8
        uses: actions/setup-java@v1
        with:
          java-version: 1.8
      - name: Build with Gradle
        run: ./gradlew build

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 1.8 JDK.
  3. The "Build with Gradle" step runs the gradlew wrapper script to ensure that your code builds, tests pass, and a package can be created.

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

Running on a different operating system

The starter workflow template 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 template 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 9.0.4 of the JDK for the x64 platform, you can use the setup-java action and configure the java-version and architecture parameters to '9.0.4' and x64.

steps:
  - uses: actions/checkout@v2
  - name: Set up JDK 9.0.4 for x64
    uses: actions/setup-java@v1
    with:
      java-version: '9.0.4'
      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 build task by default. In the default Gradle 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 task, you can specify those. For example, you may want to run the package task that's configured in your ci.gradle file.

steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-java@v1
    with:
      java-version: 1.8
  - name: Run the Gradle package task
    run: ./gradlew -b ci.gradle package

Caching dependencies

You can cache your dependencies to speed up your workflow runs. After a successful run, your local Gradle package cache 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 package repositories. For more information, see "Caching dependencies to speed up workflows" and the cache action.

steps:
  - uses: actions/checkout@v2
  - name: Set up JDK 1.8
    uses: actions/setup-java@v1
    with:
      java-version: 1.8
  - name: Cache Gradle packages
    uses: actions/cache@v2
    with:
      path: ~/.gradle/caches
      key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle') }}
      restore-keys: ${{ runner.os }}-gradle
  - name: Build with Gradle
    run: ./gradlew build

This workflow will save the contents of your local Gradle package cache, located in the .gradle/caches directory of the runner's home directory. The cache key will be the hashed contents of the gradle build files, so changes to them 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."

Gradle will usually create output files like JARs, EARs, or WARs in the build/libs directory. You can upload the contents of that directory using the upload-artifact action.

steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-java@v1
  - run: ./gradlew build
  - uses: actions/upload-artifact@v2
    with:
      name: Package
      path: build/libs

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