This is the official Heroku buildpack for apps that use Maven as their build tool. It's primarily used to build Java applications, but it can also build applications written in other JVM languages.

If you're using a different JVM build tool, use the appropriate buildpack:

• Gradle buildpack for Gradle projects
• Scala buildpack for sbt projects
• Clojure buildpack for Leiningen projects

• Supported Maven Versions
• Getting Started
• Application Requirements
• Configuration
  • OpenJDK Version
  • Maven Version
  • Buildpack Configuration
• Documentation

This buildpack officially supports Maven 3.x. Maven 4.x support will be added after its release.

See the Getting Started with Java on Heroku tutorial.

Your app requires a pom.xml file, or one of the other POM formats supported by the Maven Polyglot plugin, in the root directory.

Specify an OpenJDK version by creating a system.properties file in the root of your project directory and setting the java.runtime.version property. See the Java Support article for available versions and configuration instructions.

Specify a Maven version by adding the Maven Wrapper to your project. When this buildpack detects the presence of a mvnw script and a .mvn directory, it will run the Maven Wrapper instead of the default mvn command.

Alternatively, you can set the maven.version property in system.properties, though using the Maven Wrapper is the recommended approach.

Configure the buildpack by setting environment variables:

Environment Variable Description Default MAVEN_CUSTOM_GOALS Maven goals to execute clean dependency:list install MAVEN_CUSTOM_OPTS Maven command-line options -DskipTests MAVEN_JAVA_OPTS JVM options for Maven execution (none) MAVEN_SETTINGS_PATH Path to a custom settings.xml file (none) MAVEN_SETTINGS_URL URL from which to download a custom settings.xml file (none) MAVEN_HEROKU_CI_GOAL Maven goal for Heroku CI test runs test

For more information about using a custom Maven settings.xml file, see Using a Custom Maven Settings File.

For more information about using Java on Heroku, see the Java Support documentation on Dev Center.