Spring MVC: Passing a Model as an argument to a controller method VS instantiating it explicitly

Question

I have created two test methods in my MVC Controller class. In the first method the Model is being passed as an argument and in the second one I instantiate it directly. In both methods I add a single attribute to the Model instance:

@RequestMapping("/test-modelParam")
public String testMethod1(Model model) {
    model.addAttribute("testname", "testvalue");
    return "/testview";
}


@RequestMapping("/test-modelInstantiatedExplicitly")
public ModelAndView testMethod2() {
    ModelAndView mav = new ModelAndView("/testview");
    mav.addObject("testname", "testvalue");
    return mav;
}

The View gets populated correctly in both cases.

Is there any difference between the two approaches? If so, Where is it preferred to use one over the other?

Answer 1

In the end there is no difference everything will end up in a ModelAndView eventually.

When using the Model or ModelMap as a method argument it will get pre-populated with some values

1. Path Variables
2. Result of any @ModelAttribute annotated methods
3. Any @SessionAttributes available to the controller

In short it is the pre-populated model made available to the method.

The Model is always created and is merged with the one you add/create with a ModelAndView.