code: private String getRealPath( String path )
              throws IOException
      {
  
          URL fileURL = _servletContext.getResource( path );
  
          File tempDir = (File) _servletContext.getAttribute( "javax.servlet.context.tempdir" );
  
          // download file into temp dir
          if ( fileURL != null )
          {
              File newFile = File.createTempFile( "temp", ".jar", tempDir );
              if ( download( fileURL, newFile ) )
              {
                  String filePath = newFile.getPath();
                  return filePath;
              }
          }
          return null;
      }
docs: so it can be used to generate jardiff