How to read HTTP 500 using a Spring RestTemplate client - spring-mvc

Question

A simple Spring Boot REST Controller
#PostMapping(path = "check-and-submit", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<MyOutput> checkAndSave(#RequestBody #Valid MyInput input, Errors errors){
ResponseEntity<MyOutput> result = null;
if (errors.hasErrors()) {
result = new ResponseEntity<>(MyOutput.buildErrorResponse(errors), HttpStatus.INTERNAL_SERVER_ERROR);
} else {
myDao.save(input.buildEntity());
result = new ResponseEntity<>(MyOutput.buildSuccessResponse(), HttpStatus.OK);
}
return result;
}
And the test class for it
public static void main(String[] args) {
MyInput dto = new MyInput();
// set properties
RestTemplate restTemplate = new RestTemplate();
MultiValueMap<String, String> headers = new LinkedMultiValueMap<String, String>();
headers.add("Content-Type", "application/json");
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
HttpEntity<MyInput> request = new HttpEntity<MyInput>(dto, headers);
try {
ResponseEntity<MyOutput> result = restTemplate.postForEntity(URL, request, MyOutput.class);
System.out.println(result);
} catch(Exception e) {
e.printStackTrace();
}
}
For success scenario this works fine. But, for exception scenrio, i.e. HTTP 500 this fails
org.springframework.web.client.HttpServerErrorException: 500 null
at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:97)
As suggested in one of the posts, I created a error-handler that can successfully read the response
public class TestHandler extends DefaultResponseErrorHandler {
#Override
public void handleError(ClientHttpResponse response) throws IOException {
Scanner scanner = new Scanner(response.getBody());
String data = "";
while (scanner.hasNext())
data += scanner.next();
System.out.println(data);
scanner.close();
}
}
But how can I let RestTemplate read and deserialize the response JSON even in case of HTTP 500.
Before any other human-question-flagging-bot marks this as duplicate, here's a humble explanation on how this is different from the others.
All other questions address how to handle HTTP 500, at max read the response-body. This questions is directed at if it is possible to deserialize the response as JSON as well. Such functionality is well established in frameworks such as JBoss RESTEasy. Checking how same can be achieved in Spring.

Answer 1

This should work.
try {
ResponseEntity<MyOutput> result = restTemplate.postForEntity(URL, request, MyOutput.class);
} catch(HttpServerErrorException errorException) {
String responseBody = errorException.getResponseBodyAsString();
// You can use this string to create MyOutput pojo using ObjectMapper.
}