RestTemple custom error handler not catching ResourceAccessException - spring

Question

I am using RestTemplate to make Http connection to get data from external APIs. For this I have implemented a custom error handler and set it on the restTemplate object. Below is my custom error handler
public class CustomResponseErrorHandler implements ResponseErrorHandler {
public boolean hasError(ClientHttpResponse response) throws IOException {
int rawStatusCode = response.getRawStatusCode();
if (rawStatusCode / 200 != 1) {
LOG.debug("HTTPS hasError - " + rawStatusCode + "; " + response.getStatusText() + "; " + response.getStatusCode());
return true;
}
return false;
}
public void handleError(ClientHttpResponse response) throws IOException {
int rawStatusCode = response.getRawStatusCode();
LOG.debug("HTTPS handleError - " + rawStatusCode + "; " + response.getStatusText() + "; " + response.getStatusCode());
}
}
and my RestTemplateUtils class looks like below
public class RestTemplateUtils {
RestTemplate restTemplate;
public ResponseEntity<String> restGet(String url) {
restTemplate.setErrorHandler(new CustomResponseErrorHandler());
ResponseEntity<String> response= restTemplate.getForEntity(url, String.class);
return response;
}
}
I expect that any error that gets thrown during the restTemplate.getForEntity() call should be caught and logged by the CustomResponseErrorHandler but that is not the case. When I pass in a non-existent url ResponseEntity<String> response= restTemplate.getForEntity(url, String.class); throws ResourceAccessException. What should I do if I want my custom error handler to catch a 404 in such a case? Am I missing something here or misunderstanding how custom error handler should work here?

Answer 1

If you completely give a non existing url then I don't think the code is going to the point where error handler is executed;
Looking at RestTemplate#doExecute
doExecute(URI url, #Nullable HttpMethod method, #Nullable RequestCallback requestCallback,
#Nullable ResponseExtractor<T> responseExtractor)
code
try {
ClientHttpRequest request = createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
response = request.execute();
handleResponse(url, method, response);
return (responseExtractor != null ? responseExtractor.extractData(response) : null);
}
handleResponse is where the error handler is looked for but I think yours is erroring out at request.execute();
Provide some non existing url on the server api path, then you would recieve a 404 from the server and your custom error handler gets executed.