java - Spring MVC Rest Service Controller with Error Handling done right?

Question

I was wondering how to correctly implement a Spring Controller which is supposed to serve as a REST Service. Especially I want to try and make the interface as RESTful as possible. Also i'd like to make use of HTTP Error codes so my Clients can act accordingly.

I was wondering how to implement my Methods, so they return JSON if everything works fine(in the body of the response) or toss a http error code as well as a custom reason why it didnt work(maybe errors that came from the DAO or the database). However I'm not sure which one is the right way? return a String and add the values to return to a Model, or return a HashMap and put my stuff in there? or return the objects directly? but then what if an error occures and i cannot return said Class? return null instead? I post 2-3 ways of doing it that i could imagine:

@RequestMapping(value="/addUser", method= RequestMethod.POST)
public String addUser(@RequestBody User user, HttpServletResponse response, Model model) throws Exception{

    try{
        userService.addUser(user);
        model.addAttribute("user", userService.getUser(user.getUsername(), user.getPassword()));
        return "user";
    }catch(Exception e){
        model.addAttribute("error", e.toString());
        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e.toString());
        return "error";
    }
}

Or rather this way:

@RequestMapping(value="/addUser", method= RequestMethod.POST)
public @ResponseBody Map addUser(@RequestBody User user, HttpServletResponse response){
    Map map = new HashMap();
    try{
        userService.addUser(user);
        map.put("success", true);
        map.put("username", user.getUsername());
    }catch (KeyAlreadyExistsException e){
        map.put("success", false);
        map.put("Error", e.toString());
        response.sendError(HttpServletResponse.SC_FORBIDDEN, e.toString());
    }catch(Exception e){
        map.put("success", false);
        map.put("Error", e.toString());
        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e.toString());
    }
    finally {
        return map;
    }
}

I realize code is not "just right" but i cannot figure out how to make it the way it needs to be. Maybe some experiences responses would help? Thx for the support already

Answer 1

You could also catch your exceptions with @ExceptionHandler annotated methos within your Rest Controller.

@ExceptionHandler(Exception.class)
@ResponseBody
@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public String handleException(Exception e) {
    return "return error object instead";
}

this will make your acutal controller/business logic cleaner.