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Java

This guide will help you get started with a Java project on Semaphore. If you’re new to Semaphore please read our guided tour first.

Hello world

# .semaphore/semaphore.yml
version: v1.0
name: Java example
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu2004
blocks:
  - name: Hello world
    task:
      jobs:
        - name: Run java
          commands:
            - java --version
            - mvn -v

Example project with Spring Boot and Docker

Semaphore provides a tutorial and demo application with a working CI/CD pipeline that you can use to get started quickly:

• Java Spring CI/CD tutorial
• Demo project on GitHub

Supported Java versions

Semaphore supports all versions of Java. You have the following options:

• Linux: Java and related tools are available out-of-the-box in the Ubuntu 20.04 VM image and Ubuntu 22.04 VM image.
• Docker: Use your own Docker image with the version of Java and other packages that you need.

Follow the links above for details on available language versions and additional tools.

Selecting a Java version on Linux

The Linux VM provides multiple versions of Java. You can switch between them using the sem-version tool.

For example, by entering the following into your semaphore.yml file:

sem-version java 11

If the version of Java that you need is not currently available in the Linux VM, we recommend running your jobs in a custom Docker image.

Dependency caching

Here's an example of caching dependencies using Maven. You can also cache compiled code and tests as well. The exact implementation will vary depending on your tools. In the following configuration example, we download dependencies, compile code and warm the cache in the first block, then use the cache in subsequent blocks.

version: v1.0
name: Java & Maven Example
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu2004

blocks:
  - name: Setup
    task:
      env_vars:
        # Set maven to use a local directory. This is required for
        # the cache util. It must be set in all blocks.
        - name: MAVEN_OPTS
          value: "-Dmaven.repo.local=.m2"
      jobs:
        - name: Dependencies
          commands:
            - checkout
            - cache restore
            # Download all JARs possible and compile as much as possible
            # Use -q to reduce output spam
            - mvn -q dependency:go-offline test-compile
            - cache store
  - name: Tests
    task:
      env_vars:
        - name: MAVEN_OPTS
          value: "-Dmaven.repo.local=.m2"
      prologue:
        commands:
          - checkout
          - cache restore
      jobs:
        - name: Everything
          commands:
            # Again, -q to reduce output spam. Replace with command
            # that executes tests
            - mvn -q package