How to handle empty response in Spring RestTemplate

Question

My Authorization service returs a http 204 on success and a http 401 on failure but no responseBody. I'm not able to consume this with the RestTemplate client. It fails attempting to serialize the response. The error from Jackson suggest that i turn on FAIL_ON_EMPTY_BEANS in the serializer, but how do set this in restTemplate

The client consuming the rest api

@SuppressWarnings("rawtypes") @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {      RestTemplate restTemplate = new RestTemplate();     System.out.println("\n\n\n\n ============API REQUEST INTERCEPTOR=============== \n\n\n\n\n");      if(StringUtils.isBlank(request.getHeader(AuthenticationKeys.AUTHENTICATIONTOKEN.name().toLowerCase()))){         //TODO AUTHORIZE TOKEN         ResponseEntity<AuthenticationResponse> authenticateResponse = restTemplate.getForEntity(authenticateUrl, AuthenticationResponse.class);         if(authenticateResponse.getStatusCode().is2xxSuccessful()){             //TODO SET THE TOKEN IN THE CONTEXT             return true;         }else{             //TODO DO SOME ERROR HANDLING             return false;         }     }else{         AuthorizationRequest authorizationRequest = new AuthorizationRequest();         authorizationRequest.setToken("TESTNG");         ResponseEntity<Object> authorizationResponse = restTemplate.postForEntity(authorizeUrl, request, Object.class);         if(authorizationResponse.getStatusCode().is2xxSuccessful()){             return true;         }else{             //TODO DO SOME ERROR HANDLING             if(authorizationResponse.getStatusCode().equals(HttpStatus.UNAUTHORIZED)){                 response.sendError(HttpServletResponse.SC_UNAUTHORIZED, "Oops! access to this API is not authorized to you.");             }             return false;         }     } 

The rest service

@RequestMapping(value="/authorize", method = RequestMethod.POST)     void authorize(@RequestBody @Valid AuthorizationRequest request, HttpServletResponse response){         if(request.getToken().equals("TESTING")){             response.setStatus(HttpServletResponse.SC_NO_CONTENT);         }else{             response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);         }     } } 

The exception

Caused by: com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.apache.catalina.connector.CoyoteInputStream and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: org.apache.shiro.web.servlet.ShiroHttpServletRequest["request"]->org.apache.catalina.connector.RequestFacade["inputStream"])     at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:59) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:26) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:663) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:663) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:129) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:2238) ~[jackson-databind-2.5.0.jar:2.5.0]     at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     ... 52 more 

The Attempted Fix

RestTemplate restTemplate = new RestTemplate();         List<HttpMessageConverter<?>> converters = restTemplate.getMessageConverters();         for(HttpMessageConverter<?> converter : converters){             if(converter instanceof MappingJackson2HttpMessageConverter){                 ((MappingJackson2HttpMessageConverter) converter).getObjectMapper().configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);             }         } 

The next error

org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: getInputStream() has already been called for this request (through reference chain: org.apache.shiro.web.servlet.ShiroHttpServletRequest["request"]->org.apache.catalina.connector.RequestFacade["reader"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: getInputStream() has already been called for this request (through reference chain: org.apache.shiro.web.servlet.ShiroHttpServletRequest["request"]->org.apache.catalina.connector.RequestFacade["reader"])     at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:238) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:208) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:777) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:566) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:529) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.client.RestTemplate.postForEntity(RestTemplate.java:356) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at mordeth.orchestration.interceptor.ApiRequestInterceptor.preHandle(ApiRequestInterceptor.java:120) ~[ApiRequestInterceptor.class:?]     at org.springframework.web.servlet.HandlerExecutionChain.applyPreHandle(HandlerExecutionChain.java:134) ~[spring-webmvc-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938) [spring-webmvc-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877) [spring-webmvc-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) [spring-webmvc-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868) [spring-webmvc-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at javax.servlet.http.HttpServlet.service(HttpServlet.java:646) [servlet-api.jar:?]     at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) [spring-webmvc-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) [servlet-api.jar:?]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) [catalina.jar:7.0.57]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.57]     at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat7-websocket.jar:7.0.57]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) [catalina.jar:7.0.57]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.57]     at mordeth.orchestration.controller.CorsFilter.doFilterInternal(CorsFilter.java:21) [CorsFilter.class:?]     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) [catalina.jar:7.0.57]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.57]     at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449) [shiro-web-1.2.0.jar:1.2.0]     at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365) [shiro-web-1.2.0.jar:1.2.0]     at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) [shiro-core-1.2.0.jar:1.2.0]     at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) [shiro-core-1.2.0.jar:1.2.0]     at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:380) [shiro-core-1.2.0.jar:1.2.0]     at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) [shiro-web-1.2.0.jar:1.2.0]     at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) [shiro-web-1.2.0.jar:1.2.0]     at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344) [spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261) [spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) [catalina.jar:7.0.57]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.57]     at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:67) [log4j-web-2.0.jar:2.0]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) [catalina.jar:7.0.57]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.57]     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) [catalina.jar:7.0.57]     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) [catalina.jar:7.0.57]     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503) [catalina.jar:7.0.57]     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) [catalina.jar:7.0.57]     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) [catalina.jar:7.0.57]     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) [catalina.jar:7.0.57]     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) [catalina.jar:7.0.57]     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) [catalina.jar:7.0.57]     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070) [tomcat-coyote.jar:7.0.57]     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) [tomcat-coyote.jar:7.0.57]     at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314) [tomcat-coyote.jar:7.0.57]     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [?:1.7.0_71]     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [?:1.7.0_71]     at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-coyote.jar:7.0.57]     at java.lang.Thread.run(Thread.java:745) [?:1.7.0_71] Caused by: com.fasterxml.jackson.databind.JsonMappingException: getInputStream() has already been called for this request (through reference chain: org.apache.shiro.web.servlet.ShiroHttpServletRequest["request"]->org.apache.catalina.connector.RequestFacade["reader"])     at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:210) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:177) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:190) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:671) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:663) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:129) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:2238) ~[jackson-databind-2.5.0.jar:2.5.0]     at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     ... 52 more Caused by: java.lang.IllegalStateException: getInputStream() has already been called for this request     at org.apache.catalina.connector.Request.getReader(Request.java:1239) ~[catalina.jar:7.0.57]     at org.apache.catalina.connector.RequestFacade.getReader(RequestFacade.java:505) ~[catalina.jar:7.0.57]     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_71]     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_71]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_71]     at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_71]     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:536) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:663) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:663) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:129) ~[jackson-databind-2.5.0.jar:2.5.0]     at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:2238) ~[jackson-databind-2.5.0.jar:2.5.0]     at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) ~[spring-web-4.1.4.RELEASE.jar:4.1.4.RELEASE]     ... 52 more 

Answer 1

Use String instead of AuthenticationResponse. If you get an empty response, the String value will be empty.

ResponseEntity<String> authenticateResponse = restTemplate.getForEntity(authenticateUrl, String.class); 

UPDATE: Check this link. I think this will fix your issue.

ResponseEntity<Void> response = restTemplate.getForEntity(authenticateUrl,Void.class); Void body = response.getBody();