@SuppressWarnings("unchecked")
  private Class<IPlugin> loadOnePluginClass(String className) {
	  try {
		  logger.info("Request for loading class " + className + " by " + this);
		  Class<?> loadedClass = loader.loadClass(className);
		  // check that the class is of the right type
		  if (ptype.isAssignableFrom(loadedClass)) {
			  return (Class <IPlugin>) loadedClass;
		  } else {
			  logger.warning("Class " + className +
					  " is not from the expected type" +
					  ptype.getName());
		  }
	  }
	  catch (ClassNotFoundException e) {
		  e.printStackTrace();
		  logger.warning("Plugin " + className + " not found");
	  }
	  catch (NoClassDefFoundError e ) {
		  e.printStackTrace();
		  logger.warning("Class " + className + " not defined");
	  }
	  return null;
  }