A Wercker step to run Apache Maven build tasks.
This step will download and install Maven, and then execute the goals you have requested.  You must provide your pom.xml and you may optionally also provide a settings.xml and a settings-security.xml.
Downloading and installing Maven as part of the step (rather than having it preinstalled in the box) will avoid having Maven installed in the container/image that is built by your pipeline, this includes the M2_HOME and local repository, which could result in quite a space saving, especially if you have a lot of transitive dependencies.
The box that you run this step in must either have curl, tar, gzip, and md5sum installed in it, or it must have Maven already installed in /maven.  It is preferred that Maven is not pre-installed, in order to keep the image size a small as possible.
Additionally, it must have a JDK installed in it (as Maven requires a JDK).
To use this step, include it in your wercker.yml pipeline, for example:
build:
  steps:
    - java/maven:
      goals: clean install 
      settings: my-settings.xml
      profiles: prod
After the Maven step has completed, you will need to either push your image to a repostiory, or copy any built artifacts that you want to pass to the next pipeline into the /pipeline/output directory.  Anything that you do not copy into that directory will be lost.
To push your image, use the internal/docker-push step, for example:
    - internal/docker-push:
        username: $QUAY_IO_USERNAME
        password: $QUAY_IO_PASSWORD
        repository: quay.io/myuser/myapp
        tag: 1.0.0
To pass artifacts to the next pipeline:
    - script:
      code: | 
        cp target/my-awesome-application.jar /pipeline/output
All parameters are optional unless otherwise specified.
- 
pom
The name of the Maven POM file to use. If not specified, the value is assumed to bepom.xml. - 
settings
If you wish to provide your ownsettings.xmlfile, use this parameter to specify the filename of the file you wish to have Maven use as thesettings.xml. - 
security_settings
If you wish to provide you ownsettings-security.xmlfile, use this parameter to specify the filename of the file you wish to have Maven use as thesettings-security.xml. - 
goals(required)
Specify the Maven goals to execute. This should be a space-separated list of goals (and/or phases). - 
profiles
If you wish to enable any profiles, provide a comma-separated list of profile names. - 
maven_opts
This parameter allows you to provide any settings you wish to have included in theMAVEN_OPTS. For example, you may wish to specify Maven use a larger heap by specifying something likeMAVEN_OPTS="-Xmx1024m". - 
debug
Run Maven with the debug flags (-X -e) turned on. - 
version
Specify the version of Maven that you wish to use. (Only Maven versions 3.x.x are supported). If not specified, this will default to3.5.0. - 
cache_repo
If set totruethen the Maven local repository will be placed in the Wercker cache, meaning that it will still be available in subsequent builds (unless the cache is cleared) and thereby reducing the time required to donwload all the dependencies, plugins, etc. The default value is currentlyfalsedue to bug https://github.com/wercker/wercker/issues/139, but this may be changed in the future, when that bug is resolved. 
A sample application is provided at https://github.com/markxnelson/sample-maven-step that demonstrates how to use this step.