ResponseEntityExceptionHandler returns empty response body for 401 exceptions

Question

I'm trying to implement a Rest call to an authentication server using RestTemplate and log the response in case the server returns an exception. In order to do this, I used a ResponseEntityExceptionHandler to handle HttpClientErrorException's and HttpServerErrorException's.

public Response sendRequest(Request requestBody, String url, HttpMethod httpMethod, Response responseBody) {
    RestTemplate restTemplate = new RestTemplate();
    HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(requestBody.getBody(),
            this.securityHeaders);
    ResponseEntity<? extends Response> response = restTemplate.exchange(url, httpMethod, request,
            responseBody.getClass());
    return response.getBody();
}

Currently my ResponseEntityExceptionHandler is the following

@ControllerAdvice
public class RestResponseExceptionHandler extends ResponseEntityExceptionHandler {

private static Logger log = LoggerFactory.getLogger(RestResponseExceptionHandler.class);
private HttpHeaders headers = new HttpHeaders();

@ExceptionHandler(value = { HttpClientErrorException.class, HttpServerErrorException.class })
protected ResponseEntity<Object> handleConflict(HttpStatusCodeException ex, WebRequest request) {
    ErrorMessage responseBody = new ErrorMessage();
    try {
        JSONObject bodyOfException = new JSONObject(ex.getResponseBodyAsString());
        log.warn("{}| {}", ex.getStatusCode(), bodyOfException);
        responseBody.setErrorAndDescription(bodyOfException.optString("error"),
                bodyOfException.optString("error_description"));
    } catch (JSONException e) {
        log.error("{}| Bad authentication response body | Response Body | {}", ex.getStatusCode(),
                ex.getResponseBodyAsString());
    }

    return handleExceptionInternal(ex, responseBody, headers, ex.getStatusCode(), request);
}

}

However, only for HttpStatus 401 exceptions, I get an empty Response Body.

Example of logs:

400| {"error_description":"Bad client credentials","error":"invalid_client"}

401| Bad authentication response body | Response Body | 

Does anyone know how I can obtain the response body for 401 exceptions?

Edit: When using a Postman to call the Authentication Server I get non null 401 responseBody:

{
 "error": "invalid_token",
 "error_description": "Token was not recognised"
}

Thermosphere

your log is with two different status code 400 and 401 – Droshky

Yes those are the logs for 2 different requests, one with a 401 response and another with a 400 response – Thermosphere

Answer 1

I was finally able to log the response body for 401 Exceptions. I added the dependency

org.apache.httpcomponents:httpclient

and configured Rest Template Request Factory

    restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory());

Apparently the default request factory SimpleClientHttpRequestFactory is not able to read the response body for 401 Http Status.

Thermosphere

Thanks for your response, I've been struggling with this issue as well. Cheers! – Rattan

Just a side help The class in question is docs.spring.io/spring-framework/docs/current/javadoc-api/org/… – Ophthalmology

Works like a charm. How in the world did you figured this out. – Sashasashay

Answer 2

Why do you believe an HttpStatusCodeException must have a response body? That is not the case.
Look at the constructor of RestClientResponseException, its direct superclass

 ...

 * @param responseBody the response body content (may be {@code null})
 * @param responseCharset the response body charset (may be {@code null})
 */
public RestClientResponseException(
        String message, 
        int statusCode,
        String statusText,
        @Nullable HttpHeaders responseHeaders, 
        @Nullable byte[] responseBody, 
        @Nullable Charset responseCharset) { ... }

You need to expect that case, and provide a custom response body.
The actual exception message is a good value to return as part of the body, which might be a complex object.

Bechler

Yes I know, that the responseBody can be Null. However, when I use a Postman to call the authentication server and I get a receive a non null responseBody – Thermosphere

@Thermosphere could you post the response you receive with a Postman call? – Bechler

Yes, I added it to the original post – Thermosphere

@Thermosphere Look for DefaultResponseErrorHandler#handleError. Place a breakpoint there and look at the line "byte[] body = getResponseBody(response);" – Bechler

Thank you, I did as you said and noticed that for 401 responses, the getResponseBody method was throwing an exception. Which lead me to the correct way around this. I posted the solution as a response in this post. – Thermosphere

Answer 3

I was having a similar issue with a 400 response, and the above solution using the HttpComponentsClientHttpRequestFactory() did not work. I was able to read the body by using restTemplate.setFactory(new BufferingClientHttpRequestFactory(new SimpleClientHttpRequestFactory)); instead. Not sure if anybody is having my same problem but hopefully this helps if the chosen solution doesn't work for you.

Libbie