code: protected void unpackXARToOutputDirectory(Artifact artifact, String[] includes, String[] excludes)
          throws MojoExecutionException
      {
          if (!this.outputBuildDirectory.exists()) {
              this.outputBuildDirectory.mkdirs();
          }
  
          File file = artifact.getFile();
          unpack(file, this.outputBuildDirectory, "XAR Plugin", false, includes, excludes);
      }
docs: Unpacks A XAR artifacts into the build output directory, along with the project's XAR files.
  
  @param artifact the XAR artifact to unpack.
  @throws MojoExecutionException in case of unpack error