code: public static boolean isSimpleRequestParameter(Class<?> parameterType) {
  		return ClassUtils.isPrimitiveOrWrapper(parameterType) 
  			|| (parameterType.isArray() && ClassUtils.isPrimitiveOrWrapper(parameterType.getComponentType())) 
  			|| (ClassUtils.isAssignable(parameterType, Collection.class))
  			|| ClassUtils.isAssignable(parameterType, String.class)
  			|| ClassUtils.isAssignable(parameterType, String[].class);
  	}
docs: Finds out if the supplied type is a simple element (primitive/wrapper, an primitive/wrapper array or a Collection instance)
  
  @param parameterType type to check
  @return boolean