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.