What to return if Spring MVC controller method doesn t return value

Question

I am using jQuery s   getJSON   to make asynchronous calls to my simple Spring MVC backend  Most of the Spring controller methods look like this   RequestMapping value    quot  someURL quot   method   RequestMethod POST  public  ResponseBody SomePOJO getSomeData  ModelAttribute Widget widget       RequestParam  quot type quot   String type        return someDAO getSomeData widget  type         I have things set up so that each controller returns the  ResponseBody as JSON  which is what the client-side expects  But what happens when a request isn t supposed to return any content to the client-side  Can I have   RequestMapping value    quot  updateSomeData quot  method   RequestMethod POST  public  ResponseBody void updateDataThatDoesntRequireClientToBeNotified                   If not  what s the appropriate syntax to use here

User · Answer

But as your system grows in size and functionality... i think that returning always a json is not a bad idea at all. Is more a architectural / "big scale design" matter.

You can think about returing always a JSON with two know fields : code and data. Where code is a numeric code specifying the success of the operation to be done and data is any aditional data related with the operation / service requested.

Come on, when we use a backend a service provider, any service can be checked to see if it worked well.

So i stick, to not let spring manage this, exposing hybrid returning operations (Some returns data other nothing...).. instaed make sure that your server expose a more homogeneous interface. Is more simple at the end of the day.

User · Answer

You can return  ResponseEntity  object  Using  ResponseEntity  object is very convenient both at the time of constructing the response object  that contains Response Body and HTTP Status Code  and at the time of getting information out of the response object   Methods like getHeaders    getBody     getContentType    getStatusCode   etc makes the work of reading the ResponseEntity object very easy   You should be using ResponseEntity object with a http status code of 204 No Content   which is specifically to specify that the request has been processed properly and the response body is intentionally blank  Using appropriate Status Codes to convey the right information is very important  especially if you are making an API that is going to be used by multiple client applications

User · Answer

There is nothing wrong with returning a void  ResponseBody and you should for POST requests   Use HTTP status codes to define errors within exception handler routines instead as others are mentioning success status  A normal method as you have will return a response code of 200 which is what you want  any exception handler can then return an error object and a different code  i e  500

User · Answer

Yes  you can use  ResponseBody with void return type    RequestMapping value     updateSomeData  method   RequestMethod POST   ResponseBody public void updateDataThatDoesntRequireClientToBeNotified

User · Answer

you can return void  then you have to mark the method with   ResponseStatus value   HttpStatus OK  you don t need  ResponseBody   RequestMapping value     updateSomeData  method   RequestMethod POST   ResponseStatus value   HttpStatus OK  public void updateDataThatDoesntRequireClientToBeNotified                    Only get methods return a 200 status code implicity  all others you have do one of three things     Return void and mark the method with  ResponseStatus value   HttpStatus OK  Return An object and mark it with  ResponseBody  Return an HttpEntity instance

User · Answer

You can simply return a ResponseEntity with the appropriate header    RequestMapping value     updateSomeData  method   RequestMethod POST  public ResponseEntity updateDataThatDoesntRequireClientToBeNotified            return new ResponseEntity HttpStatus OK

User · Answer

Here is example code what I did for an asynchronous method   RequestMapping value     import   method   RequestMethod POST   ResponseStatus value   HttpStatus OK  public void importDataFromFile  RequestParam  file   MultipartFile file         accountingSystemHandler importData file  assignChargeCodes       You do not need to return any thing from your method all you need to use this annotation so that your method should return OK in every case   ResponseStatus value   HttpStatus OK

[java] What to return if Spring MVC controller method doesn't return value?

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