How to respond with HTTP 400 error in a Spring MVC ResponseBody method returning String

Question

I m using Spring MVC for a simple JSON API  with  ResponseBody based approach like the following   I already have a service layer producing JSON directly     RequestMapping value     matches  matchId    produces    application json    ResponseBody public String match  PathVariable String matchId        String json   matchService getMatchJson matchId       if  json    null               TODO  how to respond with e g  400  bad request             return json      Question is  in the given scenario  what is the simplest  cleanest way to respond with a HTTP 400 error   I did come across approaches like   return new ResponseEntity HttpStatus BAD REQUEST        but I can t use it here since my method s return type is String  not ResponseEntity

User · Answer

Here s a different approach  Create a custom Exception annotated with  ResponseStatus  like the following one    ResponseStatus code   HttpStatus NOT FOUND  reason    Not Found   public class NotFoundException extends Exception        public NotFoundException               And throw it when needed    RequestMapping value     matches  matchId    produces    application json    ResponseBody public String match  PathVariable String matchId        String json   matchService getMatchJson matchId       if  json    null            throw new NotFoundException              return json      Check out the Spring documentation here  http   docs spring io spring docs current spring-framework-reference htmlsingle  mvc-ann-annotated-exceptions

User · Answer

I m using this in my spring boot application    RequestMapping value     matches  matchId    produces    application json    ResponseBody public ResponseEntity lt   gt  match  PathVariable String matchId   RequestBody String body              HttpServletRequest request  HttpServletResponse response         Product p      try         p   service getProduct request getProductId           catch Exception ex           return new ResponseEntity lt String gt  HttpStatus BAD REQUEST              return new ResponseEntity p  HttpStatus OK

User · Answer

change your return type to ResponseEntity lt  gt   then you can use below for 400  return new ResponseEntity lt  gt  HttpStatus BAD REQUEST     and for correct request  return new ResponseEntity lt  gt  json HttpStatus OK     UPDATE 1  after spring 4 1 there are helper methods in ResponseEntity could be used as  return ResponseEntity status HttpStatus BAD REQUEST  body null     and  return ResponseEntity ok json

User · Answer

Easiest way is to throw a ResponseStatusException       RequestMapping value     matches  matchId    produces    application json        ResponseBody     public String match  PathVariable String matchId   RequestBody String body            String json   matchService getMatchJson matchId           if  json    null                throw new ResponseStatusException HttpStatus NOT FOUND                     return json

User · Answer

As mentioned in some answers  there is the ability to create an exception class for each HTTP status that you want to return   I don t like the idea of having to create a class per status for each project   Here is what I came up with instead    Create a generic exception that accepts an HTTP status Create an Controller Advice exception handler   Let s get to the code  package com javaninja cam exception   import org springframework http HttpStatus           The exception used to return a status and a message to the calling system      author norrisshelton      SuppressWarnings  ClassWithoutNoArgConstructor   public class ResourceException extends RuntimeException        private HttpStatus httpStatus   HttpStatus INTERNAL SERVER ERROR                  Gets the HTTP status code to be returned to the calling system          return http status code   Defaults to HttpStatus INTERNAL SERVER ERROR  500           see HttpStatus             public HttpStatus getHttpStatus             return httpStatus                        Constructs a new runtime exception with the specified HttpStatus code and detail message         The cause is not initialized  and may subsequently be initialized by a call to   link  initCause           param httpStatus the http status   The detail message is saved for later retrieval by the   link                           getHttpStatus    method          param message    the detail message  The detail message is saved for later retrieval by the   link                           getMessage    method          see HttpStatus             public ResourceException HttpStatus httpStatus  String message            super message           this httpStatus   httpStatus            Then I create a controller advice class  package com javaninja cam spring    import com javaninja cam exception ResourceException   import org springframework http ResponseEntity  import org springframework web bind annotation ExceptionHandler           Exception handler advice class for all SpringMVC controllers      author norrisshelton     see org springframework web bind annotation ControllerAdvice      org springframework web bind annotation ControllerAdvice public class ControllerAdvice                   Handles ResourceExceptions for the SpringMVC controllers          param e SpringMVC controller exception          return http response entity         see ExceptionHandler              ExceptionHandler ResourceException class      public ResponseEntity handleException ResourceException e            return ResponseEntity status e getHttpStatus    body e getMessage               To use it  throw new ResourceException HttpStatus BAD REQUEST   My message      http   javaninja net 2016 06 throwing-exceptions-messages-spring-mvc-controller

User · Answer

I think this thread actually has the easiest  cleanest solution  that does not sacrifice the JSON martialing tools that Spring provides   https   stackoverflow com a 16986372 1278921

User · Answer

Not necessarily the most compact way of doing this  but quite clean IMO  if json    null        throw new BadThingException            ExceptionHandler BadThingException class   ResponseStatus value   HttpStatus BAD REQUEST  public  ResponseBody MyError handleException BadThingException e        return new MyError  That doesnt work        Edit you can use  ResponseBody in the exception handler method if using Spring 3 1   otherwise use a ModelAndView or something   https   jira springsource org browse SPR-6902

User · Answer

I would change the implementation slightly   First  I create a UnknownMatchException     ResponseStatus HttpStatus NOT FOUND  public class UnknownMatchException extends RuntimeException       public UnknownMatchException String matchId            super  Unknown match      matchId             Note the use of  ResponseStatus  which will be recognized by Spring s ResponseStatusExceptionResolver  If the exception is thrown  it will create a response with the corresponding response status   I also took the liberty of changing the status code to 404 - Not Found which I find more appropriate for this use case  but you can stick to HttpStatus BAD REQUEST if you like      Next  I would change the MatchService to have the following signature   interface MatchService       public Match findMatch String matchId         Finally  I would update the controller and delegate to Spring s MappingJackson2HttpMessageConverter to handle the JSON serialization automatically  it is added by default if you add Jackson to the classpath and add either  EnableWebMvc or  lt mvc annotation-driven   gt  to your config  see the reference docs     RequestMapping value     matches  matchId    produces   MediaType APPLICATION JSON VALUE   ResponseBody public Match match  PathVariable String matchId           throws an UnknownMatchException if the matchId is not known      return matchService findMatch matchId         Note  it is very common to separate the domain objects from the view objects or DTO objects  This can easily be achieved by adding a small DTO factory that returns the serializable JSON object    RequestMapping value     matches  matchId    produces   MediaType APPLICATION JSON VALUE   ResponseBody public MatchDTO match  PathVariable String matchId        Match match   matchService findMatch matchId       return MatchDtoFactory createDTO match

User · Answer

Something like this should work  I m not sure whether or not there is a simpler way    RequestMapping value     matches  matchId    produces    application json    ResponseBody public String match  PathVariable String matchId   RequestBody String body              HttpServletRequest request  HttpServletResponse response        String json   matchService getMatchJson matchId       if  json    null            response setStatus  HttpServletResponse SC BAD REQUEST               return json

User · Answer

You also could just throw new HttpMessageNotReadableException  error description   to benefit from Spring s default error handling   However  just as is the case with those default errors  no response body will be set   I find these useful when rejecting requests that could reasonably only have been handcrafted  potentially indicating a malevolent intent  since they obscure the fact that the request was rejected based on a deeper  custom validation and its criteria   Hth  dtk

User · Answer

Another approach is to use  ExceptionHandler with  ControllerAdvice to centralize all your handlers in the same class  if not you must put the handler methods in every controller you want to manage an exception   Your handler class    ControllerAdvice public class MyExceptionHandler extends ResponseEntityExceptionHandler       ExceptionHandler MyBadRequestException class    public ResponseEntity lt MyError gt  handleException MyBadRequestException e        return ResponseEntity          badRequest            body new MyError HttpStatus BAD REQUEST  e getDescription              Your custom exception   public class MyBadRequestException extends RuntimeException      private String description     public MyBadRequestException String description        this description   description         public String getDescription         return this description          Now you can throw exceptions from any of your controllers  and you can define other handlers inside you advice class

User · Answer

With Spring Boot  I m not entirely sure why this was necessary  I got the  error fallback even though  ResponseBody was defined on an  ExceptionHandler   but the following in itself did not work    ResponseBody  ResponseStatus HttpStatus BAD REQUEST   ExceptionHandler IllegalArgumentException class  public ErrorMessage handleIllegalArguments HttpServletRequest httpServletRequest  IllegalArgumentException e        log error  Illegal arguments received    e       ErrorMessage errorMessage   new ErrorMessage        errorMessage code   400      errorMessage message   e getMessage        return errorMessage      It still threw an exception  apparently because no producible media types were defined as a request attribute      AbstractMessageConverterMethodProcessor  SuppressWarnings  unchecked   protected  lt T gt  void writeWithMessageConverters T value  MethodParameter returnType          ServletServerHttpRequest inputMessage  ServletServerHttpResponse outputMessage          throws IOException  HttpMediaTypeNotAcceptableException  HttpMessageNotWritableException        Class lt   gt  valueType   getReturnValueType value  returnType       Type declaredType   getGenericType returnType       HttpServletRequest request   inputMessage getServletRequest        List lt MediaType gt  requestedMediaTypes   getAcceptableMediaTypes request       List lt MediaType gt  producibleMediaTypes   getProducibleMediaTypes request  valueType  declaredType   if  value    null  amp  amp  producibleMediaTypes isEmpty              throw new IllegalArgumentException  No converter found for return value of type      valueType         lt -- throws                  SuppressWarnings  unchecked   protected List lt MediaType gt  getProducibleMediaTypes HttpServletRequest request  Class lt   gt  valueClass  Type declaredType        Set lt MediaType gt  mediaTypes    Set lt MediaType gt   request getAttribute HandlerMapping PRODUCIBLE MEDIA TYPES ATTRIBUTE       if   CollectionUtils isEmpty mediaTypes             return new ArrayList lt MediaType gt  mediaTypes     So I added them    ResponseBody  ResponseStatus HttpStatus BAD REQUEST   ExceptionHandler IllegalArgumentException class  public ErrorMessage handleIllegalArguments HttpServletRequest httpServletRequest  IllegalArgumentException e        Set lt MediaType gt  mediaTypes   new HashSet lt  gt         mediaTypes add MediaType APPLICATION JSON UTF8       httpServletRequest setAttribute HandlerMapping PRODUCIBLE MEDIA TYPES ATTRIBUTE  mediaTypes       log error  Illegal arguments received    e       ErrorMessage errorMessage   new ErrorMessage        errorMessage code   400      errorMessage message   e getMessage        return errorMessage      And this got me through to have a  supported compatible media type   but then it still didn t work  because my ErrorMessage was faulty   public class ErrorMessage       int code       String message      JacksonMapper did not handle it as  convertable   so I had to add getters setters  and I also added  JsonProperty annotation  public class ErrorMessage        JsonProperty  code       private int code        JsonProperty  message       private String message       public int getCode             return code             public void setCode int code            this code   code             public String getMessage             return message             public void setMessage String message            this message   message            Then I received my message as intended    code  400  message   An   url   parameter must be defined

[java] How to respond with HTTP 400 error in a Spring MVC @ResponseBody method returning String?

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