How to handle Exception and return proper HTTP code in Spring webflux? - spring-boot

Question

I have a method which gives response using Mono.fromfuture(result) and which throws CustomException with 400 as status.
Now in my service class, when I call that method, the error and code I am throwing there is not getting propagated to my client(postman). Only the message is what I am seeing.
I am getting this below format: -
{
"timestamp": "2019-02-01T11:13:32.748+0000",
"path": "/some_url",
"status": 500,
"error": "Internal Server Error",
"message": "Unable to fetch Response"
}
Expectation (what I want to achieve) : -
{
"timestamp": "2019-02-01T11:13:32.748+0000",
"path": "/some_url",
"status": 400, // (my own status)
"error": "INVALID_ARGUMENT", // (my own error)
"message": "Unable to fetch Response"
}
My Code:-
public Mono<ResponseObject> fetchResponse(arg) {
return Mono.just(somedata which will give exception)
.flatMap(k -> callExternalService(k))
.onErrorMap(e -> Mono.error(
new BusinessException("Unable to fetch Response", e))
*/* e here is giving :-
"code" : 400,
"message" : "Request contains an invalid argument.",
"status" : "INVALID_ARGUMENT" */*
}

Answer 1

Have you looked at the documentation of the Response class?
You can create a Response of your own, using the static methods in the doc, and send it, instead of Mono.error, in the onErrorMap.
You have to return something like below:
ServerResponse.ok().contentType(MediaType.APPLICATION_JSON).body(klass, Klass.class);
ServerResponse.status(status).build();//read doc and set for yourself
You can also check this link.