When handler code isn't trivial, then this code should be considered to be moved to a separate service class. This makes the business code both better to test and reusable.

This is a simple example:

@RequestMapping(value="/service/{id}/{command}")
public ModelAndView handle(
                    @PathVariable("id") Integer id,
                    @PathVariable("command") String command) {

  Object result = getService()
                  .performComplexComputation(id, command);

  return HandlerHelper.createModel(result);
}

It's possible to use Spring's mechanism for an annotation based automatic instantiation and autowiring of handlers and other beans. This requires the bean classes to be annotated with @Controller, @Service, @Inject etc. as well as using a <context:component-scan> declaration.

Several handler methods may exist in the same class for the same URI path if they handle different request methods (such as GET or POST)