@RequestParam spring MVC , make one of two request params mandatory

Question

I am writing a service wherein I take in either an id or a location and I want to enforce the constraint that either the id or the location must be specified in my @Controller

@Controller
public class HelloController {
    @RequestMapping(value="/loc.json",method = RequestMethod.GET)
    public @ResponseBody String localiaztionRequest(@RequestParam(value = "location",  required = false) String callback
            ,@RequestParam(value = "id",  required = false) String uuid
            ,@RequestParam(value = "callback",  required = false) String callback) {
        //model.addAttribute("message", "Hello world!");

        return "hello";
    }

For clarity, I want each request to send either the location parameter or the id parameter. How do I enforce such a constraint on a pair of input parameters? Also as an aside could someone please explain to me the use of ModelMap , what is the effect of model.addAttribute("message","Hello World!") ? Sorry if the questions seem rather naive, I'm extremely new to the spring framework.

Thanks in advance.

Answer 1

I think you should split it into two different controller methods

@RequestMapping(value="/loc.json",method = RequestMethod.GET, params={"location"})
public @ResponseBody String localizationRequestByLoc(@RequestParam String location, @RequestParam String callback) {
    //model.addAttribute("message", "Hello world!");

    return "hello";
}

@RequestMapping(value="/loc.json",method = RequestMethod.GET, params={"id"})
public @ResponseBody String localizationRequestById(@RequestParam String id, @RequestParam String callback) {
    //model.addAttribute("message", "Hello world!");

    return "hello";
}