title: Throwing ResourceAccessException vs HttpClientErrorException for RestTemplate client in Spring
body: <p>Using Spring 4.3.1 on Apache Tomcat 8.5, We have implemented a REST server that handles GET, POST &amp; PUT requests. The POST request is handled in the form:</p>
  
  <pre><code>@POST
  @Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
  @Transactional
  public Response postMethod(final MyDomain object) {
       domainHandler.createDomain(object);
       return Response.status(201).entity(object).build();
  }
  </code></pre>
  
  <p>During handling POST request on the server side, the WebApplicationException is thrown, which is handled by:</p>
  
  <pre><code>@Provider
  public class WebExceptionMapper implements ExceptionMapper&lt;WebApplicationException&gt; {
       @Override
       public Response toResponse(WebApplicationException exception) {
            int httpStatus = exception.getResponse().getStatus();
            ErrorMessage em = new WebErrorMessage(exception.getMessage());
            return Response.status(httpStatus).entity(em).build();
       }
  }
  </code></pre>
  
  <p>On the client side:</p>
  
  <pre><code>response = rest.exchange(requestURL, method, requestEntity, MyDomain.class);
  </code></pre>
  
  <p>the ResourceAccessException is thrown:</p>
  
  <pre><code>2017-07-25 15:46:41,489 ERROR [com.my.code.web.presentation.ManagementController:63] (http-nio-8080-exec-7#34): Internal exception occured with cause:
  org.springframework.web.client.ResourceAccessException: I/O error on POST request for "http://localhost:8080/": Server returned HTTP response code: 500 for URL: http://localhost:8080/; nested exception is java.io.IOException: Server returned HTTP response code: 500 for URL: http://localhost:8080/
       at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:633) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:580) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:498) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at com.my.code.web.integration.client.rest.FeedbackRestClient.callForApiCreateFeedback(FeedbackRestClient.java:218) ~[classes/:?]
       at com.my.code.web.integration.client.rest.FeedbackRestClient.pushFeedbackData(FeedbackRestClient.java:70) ~[classes/:?]
       at com.my.code.web.presentation.FeedbackController.feedback(FeedbackController.java:91) ~[classes/:?]
       at sun.reflect.GeneratedMethodAccessor72.invoke(Unknown Source) ~[?:?]
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_131]
       at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_131]
       at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114) ~[spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) [spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) [spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) [servlet-api.jar:?]
       at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [servlet-api.jar:?]
       at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [catalina.jar:8.5.16]
       at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [catalina.jar:8.5.16]
       at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [catalina.jar:8.5.16]
       at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [catalina.jar:8.5.16]
       at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-websocket.jar:8.5.16]
       at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [catalina.jar:8.5.16]
       at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [catalina.jar:8.5.16]
       at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [catalina.jar:8.5.16]
       at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [catalina.jar:8.5.16]
       at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [catalina.jar:8.5.16]
       at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [catalina.jar:8.5.16]
       at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) [catalina.jar:8.5.16]
       at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624) [catalina.jar:8.5.16]
       at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [catalina.jar:8.5.16]
       at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [catalina.jar:8.5.16]
       at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) [tomcat-coyote.jar:8.5.16]
       at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-coyote.jar:8.5.16]
       at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-coyote.jar:8.5.16]
       at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) [tomcat-coyote.jar:8.5.16]
       at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-coyote.jar:8.5.16]
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_131]
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_131]
       at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-util.jar:8.5.16]
       at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]
  Caused by: java.io.IOException: Server returned HTTP response code: 400 for URL: http://localhost:8080/
       at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1876) ~[?:1.8.0_131]
       at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1474) ~[?:1.8.0_131]
       at org.springframework.http.client.SimpleClientHttpResponse.getBody(SimpleClientHttpResponse.java:85) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at com.my.code.web.integration.client.rest.BufferingClientHttpResponseWrapper.getBody(BufferingClientHttpResponseWrapper.java:46) ~[classes/:?]
       at com.my.code.web.integration.client.rest.LoggingRequestInterceptor.traceResponse(LoggingRequestInterceptor.java:66) ~[classes/:?]
       at com.my.code.web.integration.client.rest.LoggingRequestInterceptor.intercept(LoggingRequestInterceptor.java:34) ~[classes/:?]
       at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:85) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.http.client.InterceptingClientHttpRequest.executeInternal(InterceptingClientHttpRequest.java:69) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:619) ~[spring-web-4.3.1.RELEASE.jar:4.3.1.RELEASE]
       ... 47 more
  </code></pre>
  
  <blockquote>
    <p>Question:</p>
  </blockquote>
  
  <p>Why the exception <code>org.springframework.web.client.ResourceAccessException</code> is thrown, but not <code>org.springframework.web.client.HttpClientErrorException</code>, what's happening for handling the GET request when <code>WebApplicationException</code> occurs?</p>
  
  <p>The <code>ResourceAccessException</code> exception does not have methods that allow me to read the HTTP status, eg <code>getRawStatusCode ()</code>, <code>getResponseHeaders()</code>, etc.</p>