title: Spring Boot REST Service: JSON Deserialization Not Working
body: <p>I'm working on a REST service using spring-boot and Kotlin.  (I should mention it's my first time using both.)  I'm having trouble getting Jackson to deserialize JSON from a POST request using this code:</p>
  
  <pre><code>@RequestMapping("cloudservice/login/{uuid}", method = arrayOf(RequestMethod.POST))
  fun login(@PathVariable(value="uuid")uuid: String, @RequestBody user: CloudServiceUser ) : ResponseEntity&lt;CloudServiceUser&gt; {
  
      val cloudServiceFactory : Class&lt;CloudServiceFactory&gt; = cloudServiceRepository.cloudServiceExtensions[UUID.fromString(uuid)] ?: throw InvalidPathVariableException("Invalid UUID.")
      var token : String
      try {
          token = cloudServiceFactory.newInstance().authenticationService.login(user.userId, user.password)
      } catch (e:Exception ){
          throw CloudServiceException(e.message)
      }
  
      return ResponseEntity(CloudServiceUser(userId=user.userId, password = "", token = token),HttpStatus.OK)
  }
  </code></pre>
  
  <p>The user object is simply:</p>
  
  <pre><code>data class CloudServiceUser(val userId: String, val password:String, val token:String)
  </code></pre>
  
  <p>I get the error</p>
  
  <pre><code>org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not construct instance of com.irotsoma.cloudbackenc.cloudservice.CloudServiceUser: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
   at [Source: java.io.PushbackInputStream@682b15d6; line: 1, column: 2]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.irotsoma.cloudbackenc.cloudservice.CloudServiceUser: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
   at [Source: java.io.PushbackInputStream@682b15d6; line: 1, column: 2]
      at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:229) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:213) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:197) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:147) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:125) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:99) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:161) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:961) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ApplicationContextHeaderFilter.doFilterInternal(EndpointWebMvcAutoConfiguration.java:261) [spring-boot-actuator-1.3.5.RELEASE.jar:1.3.5.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:115) [spring-boot-actuator-1.3.5.RELEASE.jar:1.3.5.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:103) [spring-boot-actuator-1.3.5.RELEASE.jar:1.3.5.RELEASE]
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1502) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1458) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_92]
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_92]
      at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.0.33.jar:8.0.33]
      at java.lang.Thread.run(Thread.java:745) [na:1.8.0_92]
  Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.irotsoma.cloudbackenc.cloudservice.CloudServiceUser: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
   at [Source: java.io.PushbackInputStream@682b15d6; line: 1, column: 2]
      at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:261) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1420) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1011) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1201) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789) ~[jackson-databind-2.8.0.jar:2.8.0]
      at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2913) ~[jackson-databind-2.8.0.jar:2.8.0]
      at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:226) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
      ... 66 common frames omitted
  </code></pre>
  
  <p>However, the serializing in the return statement works just fine to serialize to a JSON object and sends the response.  It's just the deserialization that isn't working.</p>
  
  <p>If I change the body variable to a String and manually create mapper, it also works fine. Like this:</p>
  
  <pre><code>@RequestMapping("cloudservice/login/{uuid}", method = arrayOf(RequestMethod.POST))
  fun login(@PathVariable(value="uuid")uuid: String, @RequestBody user: String ) : ResponseEntity&lt;CloudServiceUser&gt; {
  
      val mapper = ObjectMapper().registerModule(KotlinModule())
      val mapperData: CloudServiceUser = mapper.readValue(user)
  
  
      val cloudServiceFactory : Class&lt;CloudServiceFactory&gt; = cloudServiceRepository.cloudServiceExtensions[UUID.fromString(uuid)] ?: throw InvalidPathVariableException("Invalid UUID.")
      var token : String
      try {
          token = cloudServiceFactory.newInstance().authenticationService.login(mapperData.userId, mapperData.password)
      } catch (e:Exception ){
          throw CloudServiceException(e.message)
      }
  
      return ResponseEntity(CloudServiceUser(userId=mapperData.userId, password = "", token = token),HttpStatus.OK)
  }
  </code></pre>
  
  <p>Any ideas?</p>
  
  <p>It's an open source project, so feel free to browse it if you need more info:  <a href="https://github.com/irotsoma/cloudbackenc" rel="noreferrer">https://github.com/irotsoma/cloudbackenc</a>.  Note that it is in a very early state at the moment.</p>
  
  <p>EDIT:  Just wanted to add a note about my troubles with Integration tests as noted in comments on the accepted answer.  I ended up never getting the integration test to be able to deserialize the response (though the REST controller side of things worked fine just like in production).  So I found a workaround using a Map object, which for some reason it was able to deserialize to, and then manually processing it rather than using the class object.  Since it's just a problem with the test and not the code being tested, this was fine for me.</p>
  
  <pre><code>val returnValue = template.postForEntity("REQUEST URL", httpEntity, Map::class.java)
  </code></pre>