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README.md

Buildpack: Java

This is a 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.

How it works

The buildpack will detect your app as Java if it has a pom.xml file 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.

  $ ls
  Procfile  pom.xml  src

  $ scalingo create java-app

  $ git push scalingo master
  ...
  -----> Java app detected
  -----> Installing OpenJDK 1.8... done
  -----> Installing Maven 3.2.5... done
  -----> Installing settings.xml... done
  -----> executing /app/tmp/repo.git/.cache/.maven/bin/mvn -B -Duser.home=/tmp/build_19z6l4hp57wqm -Dmaven.repo.local=/app/tmp/repo.git/.cache/.m2/repository -s /app/tmp/repo.git/.cache/.m2/settings.xml -DskipTests=true clean install
         [INFO] Scanning for projects...
         [INFO]
         [INFO] ------------------------------------------------------------------------
         [INFO] Building readmeTest 1.0-SNAPSHOT
         [INFO] ------------------------------------------------------------------------

Examples

Configuration

Choose a JDK

Create a system.properties file in the root of your project directory and set java.runtime.version=1.8.

Example:

$ ls
Procfile pom.xml src

$ echo "java.runtime.version=1.8" > system.properties

$ git add system.properties && git commit -m "Java 8"

$ git push scalingo master
...
-----> Java app detected
-----> Installing OpenJDK 1.8... done
-----> Installing Maven 3.3.9... done
...

Choose a Maven Version

You can define a specific version of Maven for Scalingo to use by adding the Maven Wrapper to your project. When this buildpack detects the precense of a mvnw script and a .mvn directory, it will run the Maven Wrapper instead of the default mvn command.

If you need to override this, the system.properties file also allows for a maven.version entry (regardless of whether you specify a java.runtime.version entry). For example:

java.runtime.version=1.8
maven.version=3.3.9

Customize Maven

There are three config variables that can be used to customize the Maven execution:

  • MAVEN_CUSTOM_GOALS: set to clean dependency:list install by default
  • MAVEN_CUSTOM_OPTS: set to -DskipTests by default
  • MAVEN_JAVA_OPTS: set to -Xmx1024m by default

These variables can be set like this:

$ scalingo env-set MAVEN_CUSTOM_GOALS="clean package"
$ scalingo env-unset MAVEN_CUSTOM_OPTS="--update-snapshots -DskipTests=true"
$ scalingo env-set MAVEN_JAVA_OPTS="-Xss2g"

Development

To make changes to this buildpack, fork it on Github. Push up changes to your fork, then create a new Scalingo app to test it, or configure an existing app to use your buildpack:

# Create a new Scalingo app that uses your buildpack
scalingo create new-app

# Configure an existing Scalingo app to use your buildpack
scalingo env-set GITHUB_URL=<your-github-url>

# You can also use a git branch!
scalingo env-set GITHUB_URL=<your-github-url>#your-branch

For example if you want to have maven available to use at runtime in your application, you can copy it from the cache directory to the build directory by adding the following lines to the compile script:

for DIR in ".m2" ".maven" ; do
  cp -r $CACHE_DIR/$DIR $BUILD_DIR/$DIR
done

This will copy the local maven repo and maven binaries into your slug.

Commit and push the changes to your buildpack to your Github fork, then push your sample app to Scalingo to test. Once the push succeeds you should be able to run:

$ scalingo run bash

and then:

$ ls -al

and you'll see the .m2 and .maven directories are now present in your slug.

License

Licensed under the MIT License. See LICENSE file.