Spring Resttemplate exception handling

Question

Below is the code snippet  basically  I am trying to propagate the exception when the error code is anything other than 200   ResponseEntity lt Object gt  response   restTemplate exchange url toString   replace   version    version                       HttpMethod POST  entity  Object class               if response getStatusCode   value     200                   logger debug  Encountered Error while Calling API                    throw new ApplicationException                    However in the case of a 500 response from the server I am getting the exception   org springframework web client HttpServerErrorException  500 Internal Server Error     at org springframework web client DefaultResponseErrorHandler handleError DefaultResponseErrorHandler java 94    spring-web-4 2 3 RELEASE jar 4 2 3 RELEASE    Do I really need to wrap the rest template exchange method in try  What would then be the purpose of codes

User · Answer

I have handled this as below   try     response   restTemplate postForEntity requestUrl  new HttpEntity lt  gt  requestBody  headers   String class     catch  HttpStatusCodeException ex      response   new ResponseEntity lt String gt  ex getResponseBodyAsString    ex getResponseHeaders    ex getStatusCode

User · Answer

Spring abstracts you from the very very very large list of http status code  That is the idea of the exceptions  Take a look into org springframework web client RestClientException hierarchy     You have a bunch of classes to map the most common situations when dealing with http responses  The http codes list is really large  you won t want write code to handle each situation  But for example  take a look into the HttpClientErrorException sub-hierarchy  You have a single exception to map any 4xx kind of error  If you need to go deep  then you can  But with just catching HttpClientErrorException  you can handle any situation where bad data was provided to the service   The DefaultResponseErrorHandler is really simple and solid  If the response status code is not from the family of 2xx  it just returns true for the hasError method

User · Answer

The code of  exchange is below   public  lt T gt  ResponseEntity lt T gt  exchange String url  HttpMethod method              HttpEntity lt   gt  requestEntity  Class lt T gt  responseType  Object    uriVariables  throws RestClientException   Exception RestClientException has HttpClientErrorException and HttpStatusCodeException exception   So in RestTemplete there may occure HttpClientErrorException and HttpStatusCodeException exception  In exception object you can get exact error message using this way  exception getResponseBodyAsString    Here is the example code   public Object callToRestService HttpMethod httpMethod  String url  Object requestObject  Class lt   gt  responseObject             printLog   Url       url           printLog   callToRestService Request       new GsonBuilder   setPrettyPrinting   create   toJson requestObject             try                RestTemplate restTemplate   new RestTemplate                restTemplate getMessageConverters   add new MappingJackson2HttpMessageConverter                 restTemplate getMessageConverters   add new StringHttpMessageConverter                   HttpHeaders requestHeaders   new HttpHeaders                requestHeaders setContentType MediaType APPLICATION JSON                HttpEntity lt Object gt  entity   new HttpEntity lt  gt  requestObject  requestHeaders                long start   System currentTimeMillis                 ResponseEntity lt   gt  responseEntity   restTemplate exchange url  httpMethod  entity  responseObject                printLog   callToRestService Status       responseEntity getStatusCodeValue                   printLog   callToRestService Body       new GsonBuilder   setPrettyPrinting   create   toJson responseEntity getBody                   long elapsedTime   System currentTimeMillis   - start              printLog   callToRestService Execution time      elapsedTime     Milliseconds                  if  responseEntity getStatusCodeValue      200  amp  amp  responseEntity getBody      null                    return responseEntity getBody                             catch  HttpClientErrorException exception                printLog   callToRestService Error      exception getResponseBodyAsString                   Handle exception here          catch  HttpStatusCodeException exception                printLog   callToRestService Error      exception getResponseBodyAsString                   Handle exception here                   return null          Here is the code description   In this method you have to pass request and response class  This method will automatically parse response as requested object    First of All you have to add message converter   restTemplate getMessageConverters   add new MappingJackson2HttpMessageConverter                 restTemplate getMessageConverters   add new StringHttpMessageConverter       Then you have to add requestHeader   Here is the code   HttpHeaders requestHeaders   new HttpHeaders                requestHeaders setContentType MediaType APPLICATION JSON                HttpEntity lt Object gt  entity   new HttpEntity lt  gt  requestObject  requestHeaders     Finally  you have to call exchange method   ResponseEntity lt   gt  responseEntity   restTemplate exchange url  httpMethod  entity  responseObject     For prety printing i used Gson library   here is the gradle   compile  com google code gson gson 2 4   You can just call the bellow code to get response   ResponseObject response new RestExample   callToRestService HttpMethod POST  URL HERE  new RequestObject   ResponseObject class     Here is the full working code   import com google gson GsonBuilder  import org springframework http    import org springframework http converter StringHttpMessageConverter  import org springframework http converter json MappingJackson2HttpMessageConverter  import org springframework web client HttpClientErrorException  import org springframework web client HttpStatusCodeException  import org springframework web client RestTemplate    public class RestExample        public RestExample                 public Object callToRestService HttpMethod httpMethod  String url  Object requestObject  Class lt   gt  responseObject             printLog   Url       url           printLog   callToRestService Request       new GsonBuilder   setPrettyPrinting   create   toJson requestObject             try                RestTemplate restTemplate   new RestTemplate                restTemplate getMessageConverters   add new MappingJackson2HttpMessageConverter                 restTemplate getMessageConverters   add new StringHttpMessageConverter                   HttpHeaders requestHeaders   new HttpHeaders                requestHeaders setContentType MediaType APPLICATION JSON                HttpEntity lt Object gt  entity   new HttpEntity lt  gt  requestObject  requestHeaders                long start   System currentTimeMillis                 ResponseEntity lt   gt  responseEntity   restTemplate exchange url  httpMethod  entity  responseObject                printLog   callToRestService Status       responseEntity getStatusCodeValue                   printLog   callToRestService Body       new GsonBuilder   setPrettyPrinting   create   toJson responseEntity getBody                   long elapsedTime   System currentTimeMillis   - start              printLog   callToRestService Execution time      elapsedTime     Milliseconds                  if  responseEntity getStatusCodeValue      200  amp  amp  responseEntity getBody      null                    return responseEntity getBody                             catch  HttpClientErrorException exception                printLog   callToRestService Error      exception getResponseBodyAsString                   Handle exception here          catch  HttpStatusCodeException exception                printLog   callToRestService Error      exception getResponseBodyAsString                   Handle exception here                   return null             private void printLog String message           System out println message             Thanks

User · Answer

You should catch a HttpStatusCodeException exception   try       restTemplate exchange         catch  HttpStatusCodeException exception        int statusCode   exception getStatusCode   value

User · Answer

Another solution is the one described here at the end of this post by  enlian   http   springinpractice com 2013 10 07 handling-json-error-object-responses-with-springs-resttemplate  try       restTemplate exchange        catch HttpStatusCodeException e        String errorpayload   e getResponseBodyAsString           do whatever you want   catch RestClientException e          no response payload  tell the user sth else

User · Answer

You want to create a class that implements ResponseErrorHandler and then use an instance of it to set the error handling of your rest template   public class MyErrorHandler implements ResponseErrorHandler      Override   public void handleError ClientHttpResponse response  throws IOException          your error handling here         Override   public boolean hasError ClientHttpResponse response  throws IOException                          public static void main String args        RestTemplate restTemplate   new RestTemplate      restTemplate setErrorHandler new MyErrorHandler         Also  Spring has the class DefaultResponseErrorHandler  which you can extend instead of implementing the interface  in case you only want to override the handleError method   public class MyErrorHandler extends DefaultResponseErrorHandler      Override   public void handleError ClientHttpResponse response  throws IOException          your error handling here         Take a look at its source code to have an idea of how Spring handles HTTP errors

User · Answer

A very simple solution can be  try        requestEntity   RequestEntity       get new URI  quot user String quot              return restTemplate exchange requestEntity  String class     catch  RestClientResponseException e            return ResponseEntity status e getRawStatusCode    body e getResponseBodyAsString

User · Answer

Spring cleverly treats http error codes as exceptions  and assumes that your exception handling code has the context to handle the error  To get exchange to function as you would expect it  do this       try           return restTemplate exchange url  httpMethod  httpEntity  String class         catch HttpStatusCodeException e            return ResponseEntity status e getRawStatusCode    headers e getResponseHeaders                     body e getResponseBodyAsString             This will return all the expected results from the response

User · Answer

I fixed it by overriding the hasError method from DefaultResponseErrorHandler class  public class BadRequestSafeRestTemplateErrorHandler extends DefaultResponseErrorHandler        Override     protected boolean hasError HttpStatus statusCode                if statusCode    HttpStatus BAD REQUEST                        return false                    return statusCode isError             And you need to set this handler for restemplate bean   Bean     protected RestTemplate restTemplate RestTemplateBuilder builder                return builder errorHandler new BadRequestSafeRestTemplateErrorHandler    build

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Here is my POST method with HTTPS which returns a response body for any type of bad responses   public String postHTTPSRequest String url String requestJson          SSL Context     CloseableHttpClient httpClient   HttpClients custom   setSSLHostnameVerifier new NoopHostnameVerifier    build        HttpComponentsClientHttpRequestFactory requestFactory   new HttpComponentsClientHttpRequestFactory        requestFactory setHttpClient httpClient         Initiate REST Template     RestTemplate restTemplate   new RestTemplate requestFactory       HttpHeaders headers   new HttpHeaders        headers setContentType MediaType APPLICATION JSON         Send the Request and get the response      HttpEntity lt String gt  entity   new HttpEntity lt String gt  requestJson headers       ResponseEntity lt String gt  response      String stringResponse           try           response   restTemplate postForEntity url  entity  String class           stringResponse   response getBody              catch  HttpClientErrorException e                stringResponse   e getResponseBodyAsString              return stringResponse

User · Answer

If you use pooling  http client factory  or load balancing  eureka  mechanism with your RestTemplate  you will not have the luxury of creating a new RestTemplate per class  If you are calling more than one service you cannot use setErrorHandler because if would be globally used for all your requests    In this case  catching the HttpStatusCodeException seems to be the  better option   The only other option you have is to define multiple RestTemplate instances using the  Qualifier annotation   Also - but this is my own taste - I like my error handling snuggled tightly to my calls

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