content/apt/developers/java6.apt

 ------
 Java 6 in Plugins and Shared Components
 ------
 Dennis Lundberg
 ------
 2015-02-14
 ------

~~ Licensed to the Apache Software Foundation (ASF) under one
~~ or more contributor license agreements.  See the NOTICE file
~~ distributed with this work for additional information
~~ regarding copyright ownership.  The ASF licenses this file
~~ to you under the Apache License, Version 2.0 (the
~~ "License"); you may not use this file except in compliance
~~ with the License.  You may obtain a copy of the License at
~~
~~   http://www.apache.org/licenses/LICENSE-2.0
~~
~~ Unless required by applicable law or agreed to in writing,
~~ software distributed under the License is distributed on an
~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
~~ KIND, either express or implied.  See the License for the
~~ specific language governing permissions and limitations
~~ under the License.

~~ NOTE: For help with the syntax of this file, see:
~~ https://maven.apache.org/doxia/references/apt-format.html

Java 6 in Plugins and Shared Components

  When you want to start using Java 6 features in a plugin, or a shared component,
  the process described here must be used as decided by the Maven PMC.
  
  A plugin/component can start using Java 6 features and/or dependencies when the need
  arises. If there are issues that have already been fixed, but not yet released,
  the current trunk of the plugin/component must be released first, targeting Java 5.
  In the announcement for such a final Java 5 version of the plugin/component, we inform
  the users that this is the last version that will work with Java 5.

* In JIRA

  When a plugin/component decides to switch to Java 6, you should set
  the description field for the versions in JIRA for the plugin/component, so that it
  is clear which version works with which version of Java.
  Mark the last Java 5 compatible version with "Last version to work with Java 5",
  see {{{https://issues.apache.org/jira/browse/MCHECKSTYLE/fixforversion/20631}example}}.
  Mark the first version that requires Java 6 "This version requires Java 6",
  see {{{https://issues.apache.org/jira/browse/MCHECKSTYLE/fixforversion/20762}example}}.

  Create an issue "Require Java 6" and schedule it for the first Java 6
  version, see {{{https://issues.apache.org/jira/browse/MCHECKSTYLE-277}example}}.
  Reference this issue when you check in the code changes (see below) into
  version control

* On the plugin/component site

  Specify the Java requirements in <<<index.apt.vm>>>: "This plugin/component requires Java
  $\{javaVersion\}.", see
  {{{https://svn.apache.org/viewvc/maven/plugins/trunk/maven-checkstyle-plugin/src/site/apt/index.apt.vm?r1=1650811&r2=1652771&pathrev=1658048}example}}.
  We need to use the variable $\{javaVersion\} here, because
  $\{maven.compiler.source\} does not work in a site.

* In the POM

  Make sure these 3 properties are defined, either in the project or in a
  parent:

  * javaVersion=1.6

  * maven.compiler.source=$\{javaVersion\}

  * maven.compiler.target=$\{javaVersion\}

  []

  Here is a list plugins that are defined in a parent, and that already makes
  use of the above mentioned properties. So it should be enough to just make
  sure that the effective-pom looks ok.

  * <<<maven-compiler-plugin>>> is defined in <<<maven-parent>>>, see
    {{{https://svn.apache.org/viewvc/maven/pom/tags/maven-parent-26/pom.xml?view=markup#l842}example}}

  * <<<maven-enforcer-plugin>>> and the <<<enforceBytecodeVersion>>> rule is defined in
    <<<maven-parent>>>, see
    {{{https://svn.apache.org/viewvc/maven/pom/tags/maven-parent-26/pom.xml?view=markup#l946}example}}

  * <<<maven-pmd-plugin>>> is defined in <<<maven-parent>>>, see
    {{{https://svn.apache.org/viewvc/maven/pom/tags/maven-parent-26/pom.xml?view=markup#l1069}example}}

  []

  These plugins that are not defined in a parent, so you might need
  to configure the Java version for them in the plugin/component 

~~ TODO The links in the following bullets should be changed to point to a tag, once maven-checkstyle-plugin has been released 

  * <<<animal-sniffer-maven-plugin>>> is only defined in selected plugins, see
    {{{https://svn.apache.org/viewvc/maven/plugins/trunk/maven-checkstyle-plugin/pom.xml?view=markup#l307}example in <<<maven-checkstyle-plugin>>>}}.
    We should move it to maven-parent.

  * <<<buildhelper-maven-plugin>>> is used to create the signature for
    animal-sniffer and is only defined in selected plugins, see
    {{{https://svn.apache.org/viewvc/maven/plugins/trunk/maven-checkstyle-plugin/pom.xml?view=markup#l295}example in <<<maven-checkstyle-plugin>>>}}.
    We should move it to maven-parent.

  * <<<maven-plugin-plugin>>> is only defined in selected plugins, see
    {{{https://svn.apache.org/viewvc/maven/plugins/trunk/maven-checkstyle-plugin/pom.xml?view=markup#l370}example in <<<maven-checkstyle-plugin>>>}}.
    We should move it to maven-plugins parent.

  []