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<h1>Mojo Developer Cookbook</h1>

<p> This page contains code snippets demonstrating commonly used tasks when writing Maven plug-ins. There are no guarantees that these are the 'right' way to do things, but they have worked at least once for the author(s).</p>

<h2>Commonly used components </h2>

<p>These components are commonly used, also in the following snippets.</p>

<h3>The maven project, or the effective pom.</h3>

<p>With the MavenProject object, you would be able to access a lot of things ( that is if you don't know the @component or @expression for it.
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/** @parameter default-value="${project}" */
private org.apache.maven.project.MavenProject mavenProject;
</pre></td></tr></table>
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<h3>Creating a maven project</h3>

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/** @component */
private MavenProjectBuilder mavenProjectBuilder;
</pre></td></tr></table>
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<h3>The dependencies declared in your plugin.</h3>

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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
/** @parameter default-value="${plugin.artifacts}" */
private java.util.List pluginArtifacts;
</pre></td></tr></table>
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<h3>For accessing artifacts and repositories</h3>

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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
/** @component */
private org.apache.maven.artifact.factory.ArtifactFactory artifactFactory;

/** @component */
private org.apache.maven.artifact.resolver.ArtifactResolver resolver;

/**@parameter default-value="${localRepository}" */
private org.apache.maven.artifact.repository.ArtifactRepository localRepository;

/** @parameter default-value="${project.remoteArtifactRepositories}" */
private java.util.List remoteRepositories;

/** @parameter default-value="${project.distributionManagementArtifactRepository}" */
private ArtifactRepository deploymentRepository;
</pre></td></tr></table>
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<h3>For resolving artifact verions</h3>

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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
/** @component */
private ArtifactMetadataSource artifactMetadataSource;
</pre></td></tr></table>
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<h3>Deploying and installing</h3>

/** @component */
private ArtifactInstaller installer;
</pre></td></tr></table>
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You may want to add @required and @readonly, but I dropped them to keep it short.
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The ones listed here are the common ones. But you can use other properties in default-value=&quot;${...}&quot;. See <a class="confluence-link" href="/display/MAVENUSER/MavenPropertiesGuide" data-linked-resource-id="48421" data-linked-resource-type="page" data-linked-resource-default-alias="MavenPropertiesGuide" data-base-url="http://docs.codehaus.org">MavenPropertiesGuide</a> for more info...</p>

<h2>Dependencies for Components</h2>

<p>When developing with the above mentioned commonly used components you will<br />
want to add the following dependencies to your pom.xml:
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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
&lt;dependency>
	&lt;groupId>org.apache.maven&lt;/groupId>
	&lt;artifactId>maven-artifact&lt;/artifactId>
	&lt;version>2.0&lt;/version>
	&lt;scope>compile&lt;/scope>
&lt;/dependency>
&lt;dependency>
	&lt;groupId>org.apache.maven&lt;/groupId>
	&lt;artifactId>maven-project&lt;/artifactId>
	&lt;version>2.0&lt;/version>
	&lt;scope>compile&lt;/scope>
&lt;/dependency>
</pre></td></tr></table>
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<h2>Storing Properties</h2>

<p> If you want to store properties in your mojo and make those properties accessible to other elements ( such as plugins, resource files, etc ). You can do something like this
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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
mavenProject.getProperties().put( "my.mojo.property", "my mojo value" )
</pre></td></tr></table>
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This is like adding to your pom
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<table class="wysiwyg-macro" data-macro-name="code" data-macro-default-parameter="xml" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6eG1sfQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
&lt;project>
  ...
  &lt;properties>
    &lt;my.mojo.property>my mojo value&lt;/my.mojo.property>
  &lt;/properties>
&lt;/project>
</pre></td></tr></table>
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<h2>Creating and resolving an artifact</h2>

<p> To create an artifact, use an ArtifactFactory.
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artifact = artifactFactory.createArtifactWithClassifier(groupId, artifactId, version, type, classifier);
</pre></td></tr></table>
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An artifact doesn't help you much until it's resolved (using an ArtifactResolver). This resolving process is not transitive!
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resolver.resolve( artifact, remoteRepositories, localRepository );
</pre></td></tr></table>
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Now you get the artifact file (in the local repository):
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File artifactFile = artifact.getFile();
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<h2>Resolving an artifact from a version range</h2>

<p>First you need to create the version range:</p>
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versionRange = VersionRange.createFromVersionSpec(versionSpecification);
</pre></td></tr></table>
<p>Then you need to create the artifact from the version range:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
artifact = artifactFactory.createDependentArtifact(groupId, artifactId, versionRange, type, classifier, scope);
// or
artifact = artifactFactory.createExtensionArtifact(groupId, artifactId, versionRange);
// or
artifact = artifactFactory.createPluginArtifact(groupId, artifactId, versionRange);
</pre></td></tr></table>
<p>Once you have the artifact with version range you use the ArtifactMetadataSource to retrieve the versions:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
List/*&lt;ArtifactVersion>*/ versions = artifactMetatdataSource.retrieveAvailableVersions(artifact, localRepository, remoteRepository);
</pre></td></tr></table>
<p>Then you can parse the list of versions and find the version that you are after (for example using versionRange.matchVersion) and then create a new artifact using tha version.</p>

<h2>Resolving transitively</h2>

<p>You need a MavenProject. If you don't have (the right) one, you can create it with just a groupId:artifactId:version:
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Artifact pomArtifact = artifactFactory.createArtifact(groupId, artifactId, version, classifier, "pom");
MavenProject pomProject = mavenProjectBuilder.buildFromRepository( pomArtifact, remoteRepositories, localRepositories );
</pre></td></tr></table>
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Now you can use the ArtifactResolver to resolve transitively.
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Set artifacts = pomProject.createArtifacts( this.factory, null, null);
ArtifactFilter filter = ...
ArtifactResolutionResult arr = resolver.resolveTransitively(artifacts, pomArtifact, pomProject.getManagedVersionMap(), local, remoteRepos, source, filter);
Set result = arr.getArtifacts();
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The filter is optional, and limits the resolving. Possible filters are:
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<ul>
	<li>ScopeArtifactFilter</li>
	<li>InclusionArtifactFilter</li>
	<li>ExclusionArtifactFilter</li>
	<li>TypeArtifactFilter</li>
	<li>AndArtifactFilter (to combine them)</li>
	<li>or create your own, by implementing ArtifactFilter</li>
</ul>

<h2>Running external commands</h2>

<p>Use CommandLine and CommandLineUtils from org.codehaus.plexus.util.cli
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CommandLine cl = new CommandLine("command");
cl.addArguments( new String[] { "arg1", "arg2", "arg3" } );
InputStream input = ...
StreamConsumer output = ...
StreamConsumer error = ...
int returnValue = CommandLineUtils.executeCommandLine(cl, input, output, error);
</pre></td></tr></table>
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The input parameter is optional. For the output and error StreamConsumers, you can use CommandLineUtils.StringStreamConsumer which captures the output<br />
in a String.
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<h2>Installing and deploying artifacts</h2>

<p>If you need want to install or deploy an artifact as part of a project build, you can add them to the MavenProject and they will be picked up in the install or deploy phase.
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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
project.getArtifact().setFile(file) // for the main artifact
projectHelper.attachArtifact(project, type, classifier, file) // for attached artifacts
</pre></td></tr></table>
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If you install/deploy in a standalone goal, or you need to install/deploy an artifact that is not part of the project being built, you can use the ArtifactInstaller or ArtifactDeployer.
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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
Artifact artifact = artifactFactory.createArtifactWithClassifier(groupId, artifactId, version, type, classifier);
installer.install(file, artifact, localRepository); // to install
deployer.deploy(file, artifact, deploymentRepository, localRepository); // to deploy (includes the install)
</pre></td></tr></table>
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<h2>Creating an ArtifactRepository</h2>

<p>Usually an artifact repository will be injected into your mojo. Should you need to create one yourself, you will need an ID, a URL and a layout.
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<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
ArtifactRepository repo = new DefaultArtifactRepository( "repositoryId", "http://my.repository.url", new DefaultRepositoryLayout() ); // use LegacyRepositoryLayout for an m1 repo&amp;nbsp;
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<h2>Accessing the Plexus container</h2>

<p>If you want access to the container, for doing your own component lookups, implement the org.codehaus.plexus.personality.plexus.lifecycle.phase.Contextualizable interface</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
public void contextualize( Context context ) throws ContextException {	container = (PlexusContainer) context.get( PlexusConstants.PLEXUS_KEY );}
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<p>So if you want to lookup a component, you can do something like this</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
Object myComponent = container.lookup( role, roleHint, container.getLookupRealm() );
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<h2>Getting dependency artifact path</h2>

<p>In some cases you may need to get the path of a jar artifact from a Dependency. This is how you can do it:
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Set artifacts = project.getDependencyArtifacts();
for (Iterator artifactIterator = artifacts.iterator(); artifactIterator.hasNext();) {
  Artifact artifact = (Artifact) artifactIterator.next();
  if (artifact.getGroupId().equals(dependency.getGroupId()) &amp;&amp; artifact.getArtifactId().equals(dependency.getArtifactId())) {
    return artifact.getFile().getPath();
  }
}
</pre></td></tr></table>
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In this snippet, project is the <a href="http://maven.apache.org/ref/2.0.4/maven-project/apidocs/org/apache/maven/project/MavenProject.html">MavenProject</a> instance of the project (@parameter default-value=&quot;${project}&quot;) and dependency is instance of Dependency (@parameter default-value=&quot;${project.dependencies}).
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