code: public void execute()
      {
          for ( Resource resource : resources )
          {
              // Check for relative paths in the resource configuration.
              // http://maven.apache.org/plugin-developers/common-bugs.html#Resolving_Relative_Paths
              File resourceDir = new File( resource.getDirectory() );
              if ( !resourceDir.isAbsolute() )
              {
                  resourceDir = new File( project.getBasedir(), resource.getDirectory() );
                  resource.setDirectory( resourceDir.getAbsolutePath() );
              }
  
              addResource( resource );
          }
      }
docs: Main plugin execution