Question

For example, how to handle validation errors and possible exceptions in this controller action method:

@RequestMapping(method = POST)
@ResponseBody
public FooDto create(@Valid FooDTO fooDto, BindingResult bindingResult) {
    if (bindingResult.hasErrors()) {
        return null; // what to do here?
                     // how to let the client know something has gone wrong?
    } else {
        fooDao.insertFoo(fooDto); // What to do if an exception gets thrown here?
                                  // What to send back to the client?
        return fooDto;
    }
}

Answer 1

Throw an exception if you have an error, and then use @ExceptionHandler to annotate another method which will then handle the exception and render the appropriate response.