code: private void unpackDependentXARs() throws MojoExecutionException
      {
          Set<Artifact> artifacts = this.project.getArtifacts();
          if (artifacts != null) {
              for (Artifact artifact : artifacts) {
                  if (!artifact.isOptional() && "xar".equals(artifact.getType())) {
                      unpackXARToOutputDirectory(artifact, getIncludes(), getExcludes());
                  }
              }
          }
      }
docs: Unpack XAR dependencies before pack then into it.
  
  @throws MojoExecutionException error when unpack dependencies.