This is the official Heroku buildpack for Java apps. It uses Maven 3.3.9 to build your application and OpenJDK 8 to run it. However, the JDK version can be configured as described below. The buildpack will detect your app as Java if it has a pom.xml file, or one of the other POM formats supports by the Maven Polyglot plugin, in its root directory. It will use Maven to execute the build defined by your pom.xml and download your dependencies. The .m2 folder (local maven repository) will be cached between builds for faster dependency resolution. However neither the mvn executable or the .m2 folder will be available in your slug at runtime.