Return JSON for ResponseEntity String

Question

I have a method in my controller that should returns a String in JSON  It returns JSON for non primitive types    RequestMapping value    so   method   RequestMethod GET  produces   MediaType APPLICATION JSON VALUE  ResponseEntity lt String gt  so         return new ResponseEntity lt String gt   This is a String   HttpStatus OK       The curl response is   This is a String

User · Accepted Answer

RequestMapping value    so   method   RequestMethod GET  produces   MediaType APPLICATION JSON VALUE  public  ResponseBody String so         return  This is a String

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This is a String  not a json structure key  value   try  return new ResponseEntity  quot   quot vale quot     quot This is a String quot   quot   HttpStatus OK

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public ResponseEntity lt   gt  ApiCall  PathVariable name    quot id quot   long id        JSONObject resp   new JSONObject        resp put  quot status quot   0       resp put  quot id quot   id        return new ResponseEntity lt String gt  resp toString    HttpStatus CREATED

User · Answer

The root of the problem is that Spring  via ResponseEntity  RestController  and or ResponseBody  will use the contents of the string as the raw response value  rather than treating the string as JSON value to be encoded   This is true even when the controller method uses produces   MediaType APPLICATION JSON VALUE  as in the question here   It s essentially like the difference between the following      yields  This is a String System out println  This is a String        yields   This is a String  System out println    This is a String        The first output cannot be parsed as JSON  but the second output can   Something like     myString     is probably not a good idea however  as that won t handle proper escaping of double-quotes within the string and will not produce valid JSON for any such string   One way to handle this would be to embed your string inside an object or list  so that you re not passing a raw string to Spring   However  that changes the format of your output  and really there s no good reason not to be able to return a properly-encoded JSON string if that s what you want to do   If that s what you want  the best way to handle it is via a JSON formatter such as Json or Google Gson   Here s how it might look with Gson   import com google gson Gson    RestController public class MyController      private static final Gson gson   new Gson          RequestMapping value    so   method   RequestMethod GET  produces   MediaType APPLICATION JSON VALUE      ResponseEntity lt String gt  so             return ResponseEntity ok gson toJson  This is a String

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An alternative solution is to use a wrapper for the String  for instances this   public class StringResponse       private String response      public StringResponse String response            this response   response            public String getResponse             return response            Then return this in your controller s methods   ResponseEntity lt StringResponse gt

[spring-mvc] Return JSON for ResponseEntity<String>

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