RestTemplate Status Code Handling

I was writing a  Spring Boot microservice that called an external service. If the service returned a `500`, the payload of the response had an error code that we wanted to send back to the service that called us. I was using RestTemplate so I thought I could just use:

if (responseEntity.getStatusCode().is2xxSuccessful()){
// happy path
}
if (responseEntity.getStatusCode().is5xxServerError()){
// do the error thing
}

But it’s not that easy. It seems that if the RestTemplate gets anything but a 2xx response, Spring’s default error handler will throw an exception. You won’t even get a chance to do anything with your ResponseEntitybecause the exception happens before that. I even found a recent bug report on the matter. Anyway, I had a chicken and an egg problem – I couldn’t parse the exception out because I didn’t have an entity for it and I didn’t have an entity because the response wasn’t a success. Of course, I may have to accept more status codes than just a 200 or a 500, so I wanted it to be configurable. This old blog entry led me in the right direction of making my own ErrorHandler. What I ended up doing was making an ErrorHandler where I injected the statuses I wanted to make.

I made a simple (and contrived) example on github. It’s actually very simple when you think about it.

My properties file looked like this:

good-status=OK,NOT_ACCEPTABLE

 

I used the words instead of the error codes. You could obviously change it.

The meat is in the MyResponseErrorHandler class. I injected the property is and then simply tested to see if the error existed:

@Component
public class MyResponseErrorHandler implements ResponseErrorHandler {
    private static final Logger log = LoggerFactory.getLogger(MyResponseErrorHandler.class);
 
    private List acceptableStatus;
 
    public  MyResponseErrorHandler(@Value("${good-status}") String goodStatus) {
 
        acceptableStatus = Arrays.stream(goodStatus.split(","))
                .map(HttpStatus::valueOf)
                .collect(Collectors.toList()) ;
 
 
    }
 
    @Override
    public void handleError(ClientHttpResponse response) throws IOException {
        log.error("Response error: {} {}", response.getStatusCode(), response.getStatusText());
    }
 
    @Override
    public boolean hasError(ClientHttpResponse response) throws IOException {
        return !acceptableStatus.contains(response.getStatusCode());
 
    }
}

And then I just inject the error handler in my client class and use it to construct the RestTemplate

 @Autowired
    public MyConsumerService(RestTemplateBuilder restTemplateBuilder,
                             MyResponseErrorHandler myResponseErrorHandler
                             ) {
 
        this.restTemplate = restTemplateBuilder
                   .errorHandler(myResponseErrorHandler)
                   .build();
    }

And that’s it – I didn’t do anything else.

The bug I referenced above said that this will be easier to do with WebClient in Spring 5. Of course, that means Spring Boot 2 (which, as I write this, is finally on RC1). So I hope that this will help others that are working in Spring Boot 1.5 for a while.


Also published on Medium.

One thought on “RestTemplate Status Code Handling

  1. Red says:

    Thank you for sharing this good idea

  2. Jason says:

    Thank you for sharing this as well. Was encountering the same issue you were. Like you said, now that you showed the solution it actually is pretty simple but couldn’t figure it out for the life of me.

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