Spring MVC 4 application json Content Type is not being set correctly

Question

I have a controller mapped with the following annotation    RequestMapping value     json   method   RequestMethod GET  produces    application json    ResponseBody public String bar         return     test      jsonResponseExample          I return a valid JSON string however  the content-type when I view the response on Chrome Dev Tools in browser is not application json but just plain text html  Why is the content type not being set   My web xml    lt  xml version  1 0  encoding  UTF-8   gt   lt web-app metadata-complete  true  version  3 0      xmlns  http   java sun com xml ns javaee  xmlns xsi  http   www w3 org 2001 XMLSchema-instance      xsi schemaLocation  http   java sun com xml ns javaee http   java sun com xml ns javaee web-app 3 0 xsd  gt        lt display-name gt Spring MVC Web Application lt  display-name gt        lt servlet gt           lt servlet-name gt dispatcher lt  servlet-name gt           lt servlet-class gt org springframework web servlet DispatcherServlet lt  servlet-class gt           lt load-on-startup gt 1 lt  load-on-startup gt       lt  servlet gt        lt  -- static assets -- gt       lt servlet-mapping gt           lt servlet-name gt default lt  servlet-name gt           lt url-pattern gt   js lt  url-pattern gt       lt  servlet-mapping gt       lt servlet-mapping gt           lt servlet-name gt default lt  servlet-name gt           lt url-pattern gt   css lt  url-pattern gt       lt  servlet-mapping gt        lt servlet-mapping gt           lt servlet-name gt dispatcher lt  servlet-name gt           lt url-pattern gt   lt  url-pattern gt       lt  servlet-mapping gt        lt context-param gt           lt param-name gt contextConfigLocation lt  param-name gt           lt param-value gt  WEB-INF dispatcher-servlet xml lt  param-value gt       lt  context-param gt        lt listener gt           lt listener-class gt org springframework web context ContextLoaderListener lt  listener-class gt       lt  listener gt   lt  web-app gt    My dispatcher-servlet xml      lt  xml version  1 0  encoding  UTF-8   gt   lt beans xmlns  http   www springframework org schema beans      xmlns context  http   www springframework org schema context      xmlns xsi  http   www w3 org 2001 XMLSchema-instance  xmlns p  http   www springframework org schema p      xsi schemaLocation       http   www springframework org schema beans          http   www springframework org schema beans spring-beans-4 1 xsd     http   www springframework org schema context      http   www springframework org schema context spring-context-4 1 xsd  gt         lt context annotation-config   gt        lt context component-scan base-package  com mydomain controllers    gt        lt bean id  viewResolver          class  org springframework web servlet view InternalResourceViewResolver  gt           lt property name  prefix  value   WEB-INF jsp     gt           lt property name  suffix  value   jsp    gt       lt  bean gt   lt  beans gt    Using WildFly 8 1 as my app server

User · Answer

Not exactly for this OP  but for those who encountered 404 and cannot set response content-type to  application json   any content-type   One possibility is a server actually responds 406 but explorer  e g   chrome  prints it as 404    If you do not customize message converter  spring would use AbstractMessageConverterMethodProcessor java  It would run   List lt MediaType gt  requestedMediaTypes   getAcceptableMediaTypes request   List lt MediaType gt  producibleMediaTypes   getProducibleMediaTypes request  valueType  declaredType     and if they do not have any overlapping  the same item   it would throw HttpMediaTypeNotAcceptableException and this finally causes 406  No matter if it is an ajax  or GET POST  or form action  if the request uri ends with a  html or any suffix  the requestedMediaTypes would be  text  that suffix    and this conflicts with producibleMediaTypes  which is usually    application json     application xml      text xml             application   xml    application json     application   json   application json     application   json   application xml      text xml             application   xml   application xml     text xml            application   xml

User · Answer

When I upgraded to Spring 4 I needed to update the jackson dependencies as follows        lt dependency gt           lt groupId gt com fasterxml jackson core lt  groupId gt           lt artifactId gt jackson-core lt  artifactId gt           lt version gt 2 5 1 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt com fasterxml jackson core lt  groupId gt           lt artifactId gt jackson-databind lt  artifactId gt           lt version gt 2 5 1 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt com fasterxml jackson core lt  groupId gt           lt artifactId gt jackson-annotations lt  artifactId gt           lt version gt 2 5 1 lt  version gt       lt  dependency gt

User · Answer

As other people have commented  because the return type of your method is String Spring won t feel need to do anything with the result   If you change your signature so that the return type is something that needs marshalling  that should help    RequestMapping value     json   method   RequestMethod GET  produces    application json    ResponseBody public Map lt String  Object gt  bar         HashMap lt String  Object gt  map   new HashMap lt String  Object gt         map put  test    jsonRestExample        return map

User · Answer

First thing to understand is that the RequestMapping produces   element in   RequestMapping value     json   method   RequestMethod GET  produces    application json     serves only to restrict the mapping for your request handlers  It does nothing else   Then  given that your method has a return type of String and is annotated with  ResponseBody  the return value will be handled by StringHttpMessageConverter which sets the Content-type header to text plain  If you want to return a JSON string yourself and set the header to application json  use a return type of ResponseEntity  get rid of  ResponseBody  and add appropriate headers to it    RequestMapping value     json   method   RequestMethod GET  produces    application json   public ResponseEntity lt String gt  bar         final HttpHeaders httpHeaders  new HttpHeaders        httpHeaders setContentType MediaType APPLICATION JSON       return new ResponseEntity lt String gt      test      jsonResponseExample      httpHeaders  HttpStatus OK         Note that you should probably have   lt mvc annotation-driven   gt     in your servlet context configuration to set up your MVC configuration with the most suitable defaults

User · Answer

I had the dependencies as specified  Greg post  I still faced the issue and could be able to resolve it by adding following additional jackson dependency    lt dependency gt       lt groupId gt com fasterxml jackson dataformat lt  groupId gt       lt artifactId gt jackson-dataformat-xml lt  artifactId gt       lt version gt 2 7 4 lt  version gt   lt  dependency gt

User · Answer

Use jackson library and  ResponseBody annotation on return type for the Controller   This works if you wish to return POJOs represented as JSon  If you woud like to return String and not POJOs as JSon please refer to Sotirious answer

[java] Spring MVC 4: "application/json" Content Type is not being set correctly

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