java-function-buildpack

The Java Function Buildpack is a Cloud Native Buildpack V3 that provides the riff Java Function Invoker to functions.

This buildpack is designed to work in collaboration with other Heroku buildpacks, which are tailored to support (and know how to build / run) languages supported by Heroku.

NOTE: Java 11 is required for building your Java Function. To specific Java 11, please add a system.properties file with java.runtime.version=11 in the body of the file. Here's an example of a Java Function project.

In Plain English

When combined with the other buildpacks present in the Heroku functions builder, users can use the pack create-builder command to build a builder image to build a Java Function image via pack build.

• The presence of a pom.xml file will result in the compilation and execution of a java function, thanks to the java invoker
• Ambiguity in the detection process will result in a build failure

Detailed Buildpack Behavior

Detection Phase

Detection passes if:

TBD

If detection passes, the buildpack will contribute an openjdk-jre key with launch metadata to instruct the openjdk-buildpack to provide a JRE. It will also add a riff-invoker-java key and handler metadata extracted from the riff metadata.

If several languages are detected simultaneously, the detect phase errors out. The override key in riff.toml can be used to bypass detection and force the use of a particular invoker.

Build Phase

If a java build has been detected

• Contributes the riff Java Invoker to a launch layer, set as the main java entry point with function.uri = <build-directory>?handler=<handler> set as an environment variable (FUNCTION_URI). This value is automatically set to point to the .jar file located in /workspace/target. At the moment, it is assumed only 1 .jar exits in this directory.

The function behavior is exposed via standard buildpack process types:

• Contributes web process
• Contributes function process

How to Build

Prerequisites

To build the java-function-buildpack you'll need

• Java 11
• Go 1.12+
• to run acceptance tests:
  • a running local docker daemon
  • the [pack](https://github.com/buildpack/pack command line tool, version >= 0.2.0.

You can build the buildpack by running

make build

This will package (with pre-downloaded cache layers) the buildpack in the root directory. That can be used as a uri in a functions-builder.toml file of a builder (see https://github.com/heroku/pack-images)

License

This buildpack is released under version 2.0 of the Apache License.