 ------
 Usage
 ------
 John Casey
 ------
 2011-02-07
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Usage

  To handle filtering this version of Maven Assembly Plugin uses
  {{{/shared/maven-filtering/index.html}Maven Filtering}} ${mavenFilteringVersion}.

  To handle archiving this version of Maven Assembly Plugin uses
  {{{/shared/maven-archiver/index.html}Maven Archiver}} ${mavenArchiverVersion}.

  This document is intended to provide instructions for using the
  maven-assembly-plugin. In order for this discussion to be useful, it's
  critical to cover two topics: configuration of the plugin - both inside the
  POM and, where possible, from the command line - and the different execution
  styles. For the sake of clarity, we'll cover configuration before execution.


* Configuration

  Getting started with the Assembly Plugin is pretty simple. If you want to use
  one of the prefabricated assembly descriptors, you configure which descriptor
  to use with the \<<<<descriptorRefs\>>>>/\<<<<descriptorRef\>>>> parameter.
  If you want to use a custom assembly descriptor, you configure the path to your
  descriptor using the \<<<<descriptors\>>>>/\<<<<descriptor\>>>> parameter.

  Note that a single invocation of the Assembly Plugin can actually
  produce assemblies from multiple descriptors, allowing you maximum flexibility
  to customize the suite of binaries your project produces. When the assembly is
  created it will use the assemblyId as the artifact's classifier and will attach
  the created assembly to the project so that it will be uploaded into the repository
  in the install and deploy phase.

  For example, imagine that our project produces a JAR. If we want to create an
  assembly binary that includes our project's dependencies, we can take
  advantage of one of the Assembly Plugin's prefabricated descriptors. You
  configure it as follows in your project's <<<pom.xml>>>:
  
+---+
<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <!-- NOTE: We don't need a groupId specification because the group is
             org.apache.maven.plugins ...which is assumed by default.
         -->
        <artifactId>maven-assembly-plugin</artifactId>
        <version>${project.version}</version>
        <configuration>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
        [...]
</project>
+---+

  Note that the Assembly Plugin allows you to specify multiple
  <<<descriptorRefs>>> at once, to produce multiple types of assemblies in a
  single invocation.
  
  Alternatively, we've created a custom assembly descriptor called
  <<<src.xml>>> in the <<<src/assembly>>> directory (see the
  {{{Resources}Resources}} section for more information). We can tell the
  Assembly Plugin to use that instead:
  
+---+
<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>${project.version}</version>
        <configuration>
          <descriptors>
            <descriptor>src/assembly/src.xml</descriptor>
          </descriptors>
        </configuration>
        [...]
</project>
+---+

  Again, note that we could specify multiple custom assembly descriptors here.
  Additionally, it's possible to specify a mixture of <<<descriptors>>> and
  <<<descriptorRefs>>> within the same configuration.
  
  <<Note:>> Many other configuration options are available for the various goals
  in the Assembly Plugin. For more information, see the
  {{{./examples/index.html}examples section}} or the {{{./plugin-info.html}plugin
  parameter documentation}}.


* Execution: Building an Assembly

  Once you've configured the various <<<descriptors>>> and <<<descriptorRefs>>>
  for the assemblies you want the project to produce, it's time to build them.
  
  In most cases, you'll want to make sure your assemblies are created as part
  of your normal build process. This ensures the assembly archives are made 
  available for installation and deployment, and that they are created during
  the release of your project. This is handled by the <<<assembly:single>>> goal.

  To bind the <<<single>>> goal to a project's build lifecycle, you can add
  this configuration (assuming you're using the <<<jar-with-dependencies>>>
  prefabricated descriptor):
  
+---+
<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>${project.version}</version>
        <configuration>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
        <executions>
          <execution>
            <id>make-assembly</id> <!-- this is used for inheritance merges -->
            <phase>package</phase> <!-- bind to the packaging phase -->
            <goals>
              <goal>single</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      [...]
</project>
+---+

  Then, to create a project assembly, simple execute the normal <<<package>>>
  phase from the default lifecycle:
  
+---+
mvn package
+---+

  When this build completes, you should see a file in the <<<target>>> directory with
  a name similar to the following:
  
+---+
target/sample-1.0-SNAPSHOT-jar-with-dependencies.jar
+---+

  Notice the artifact classifier, between the end of the version and the
  beginning of the file extension, <<<jar-with-dependencies>>>. This is the
  <<<id>>> of the assembly descriptor used to create this artifact.
  
** GOTCHA!

  In most cases, the <<<single>>> goal should be bound to the <<<package>>> phase
  of the build. However, if your assembly doesn't require binaries, or if you need
  to use one assembly as input for another, you may need to change this. While it's
  possible to assign the <<<single>>> goal to any phase of the build lifecycle, you should
  be careful to make sure the resources included in your assembly exist before that
  assembly is created.


* Advanced Configuration

** Creating an Executable JAR

  As you've no doubt noticed, the Assembly Plugin can be a very useful way to
  create a self-contained binary artifact for your project, among many other
  things. However, once you've created this self-contained JAR, you will
  probably want the ability to execute it using the <<<-jar>>> JVM switch.
  
  To accommodate this, the Assembly Plugin supports configuration of an
  <<<\<archive\>>>> element which is handled by <<<maven-archiver>>>
  (see {{{Resources}Resources}}). Using this
  configuration, it's easy to configure the <<<Main-Class>>> attribute of the
  JAR manifest:
  
+---+
<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>${project.version}</version>
        <configuration>
          [...]
          <archive>
            <manifest>
              <mainClass>org.sample.App</mainClass>
            </manifest>
          </archive>
        </configuration>
        [...]
      </plugin>
      [...]
</project>
+---+

  If we add this configuration to the <<<single>>> goal example above and
  rebuild, we will see an entry like this in the <<<META-INF/MANIFEST.MF>>> file of
  the resulting JAR:
  
+---+
[...]
Main-Class: org.sample.App
+---+

  For more information on advanced configuration for the Assembly Plugin, see
  the {{{Resources}Resources}} section.
  
** GOTCHA!

  At this point, only the <<<jar>>> and <<<war>>> assembly formats support the <<<\<archive\>>>>
  configuration element.


* {Resources}

  [[1]] For more information on writing your own assembly descriptor, read the 
        {{{./assembly.html}Assembly Descriptor}}
        
  [[2]] For more information about <<<maven-archiver>>>, look
        {{{https://maven.apache.org/shared/maven-archiver/index.html}here}}.
        
  [[3]] For more information on advanced <<<maven-assembly-plugin>>>
        configuration, see the {{{./examples/index.html}examples}}.
  
  []
