How to programmatically call a Maven-task

Here's a better solution: use the Mojo-Executor library. It exposes a simple Java API for invoking Maven plugins.

The Ant Maven tasks can give you an idea how to do it (DependenciesTask source). Another route may be the PomModuleDescriptorParser used by Ivy.

Use the Maven Invoker API. Its quick and easy.

InvocationRequest request = new DefaultInvocationRequest();
request.setPomFile( new File( "/path/to/pom.xml" ) );
request.setGoals( Collections.singletonList( "install" ) );

Invoker invoker = new DefaultInvoker();
invoker.setMavenHome(new File("/usr"));

try
{
  invoker.execute( request );
}
catch (MavenInvocationException e)
{
  e.printStackTrace();
}

pom.xml:

<dependency>
    <groupId>org.apache.maven.shared</groupId>
    <artifactId>maven-invoker</artifactId>
    <version>2.1.1</version>
</dependency>

See how org.apache.maven.plugin.testing.AbstractMojoTestCase from maven-plugin-testing-harness is implemented. Here's a code snippet from some of my tests which may be helpful.

public abstract class JAXBGenerateTest extends AbstractMojoTestCase {

    static {
        System.setProperty("basedir", getBaseDir().getAbsolutePath());
    }

    protected MavenProjectBuilder mavenProjectBuilder;

    protected void setUp() throws Exception {
        super.setUp();

        mavenProjectBuilder = (MavenProjectBuilder) getContainer().lookup(
                MavenProjectBuilder.ROLE);
    }

    protected static File getBaseDir() {...}

    /**
     * Validate the generation of a java files from purchaseorder.xsd.
     * 
     * @throws MojoExecutionException
     */
    public void testExecute() throws Exception {

        final File pom = new File(getBaseDir(),
        "src/test/resources/test-pom.xml");

        final ArtifactRepository localRepository = new DefaultArtifactRepository( "local", 

                new File(getBaseDir(), "target/test-repository").toURI().toURL().toString()             , new DefaultRepositoryLayout());


        final MavenProject mavenProject = mavenProjectBuilder.build(pom, localRepository, null);


        final XJC2Mojo generator = (XJC2Mojo) lookupMojo("generate", pom);
        generator.setProject(mavenProject);
        generator.setLocalRepository(localRepository);
        generator.setSchemaDirectory(new File(getBaseDir(),"src/test/resources/"));
        generator.setSchemaIncludes(new String[] { "*.xsd" });
        generator.setBindingIncludes(new String[] { "*.xjb" });
        generator.setGenerateDirectory(new File(getBaseDir(), "target/test/generated-sources"));
        generator.setVerbose(true);
        generator.setGeneratePackage("unittest");
        generator.setRemoveOldOutput(false);

        generator.execute();
    }

}