Spring Integration Java DSL and Http.outboundGateway: How to get the real error message JSON - spring-integration

Question

How to get the real error message JSON when the Http.outboundGateway call is failed.
For example my program does the HTTP POST. The operation fails with the error code 400 Bad Request and the real error message is (tested with the Postman):
{
"name": [
"This field is needed."
]
}
I have the error channel like this:
#Bean
private IntegrationFlow myErrorChannel() {
return f -> f.handle("myErrorHandler", "handle")
....
;
}
and the Class MyErrorHandler is like this:
#Service
public class MyErrorHandler {
#ServiceActivator
public Message<MessageHandlingException> handle(Message<MessageHandlingException> message) {
...
}
}
Does the MessageHandlingException contain the real error message?
{
"name": [
"This field is needed."
]
}
I debugged the code and checked the MessageHandlingException exception and it seems it doesn't contain the real error message. The detailMessage contains the text 400 Bad Request, but I want to know the real error message.
How to get the real error message?
Edit:
This is working (I'm assigning the real error message to the new payload):
final RestClientResponseException clientException = (RestClientResponseException) messagingHandlingException.getCause();
payload = clientException.getResponseBodyAsString();

Answer 1

The Resttemplate uses a DefaultResponseErrorHandler by default. That one has a logic like:
protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
String statusText = response.getStatusText();
HttpHeaders headers = response.getHeaders();
byte[] body = getResponseBody(response);
Charset charset = getCharset(response);
switch (statusCode.series()) {
case CLIENT_ERROR:
throw HttpClientErrorException.create(statusCode, statusText, headers, body, charset);
case SERVER_ERROR:
throw HttpServerErrorException.create(statusCode, statusText, headers, body, charset);
default:
throw new UnknownHttpStatusCodeException(statusCode.value(), statusText, headers, body, charset);
}
}
An exception from here is thrown to the HttpRequestExecutingMessageHandler which really wraps it into the MessageHandlingException.
Since you say that you can handle the last one via your MyErrorHandler, I would suggest you just take a look into the cause of the MessageHandlingException, and you'll that RestClientResponseException with all the required info from the response.