Handling Global Scenarios in Spring WebFlux - spring-webflux

Question

I have a Rest Web Client todo an API call and I handle the exceptions as given below.
I want to handle 404, 401 and 400 errors in a global way rather than handling at the individual client level. How can we achieve the same.
public Mono<ProductResponse> getProductInformation(String productId) {
return webClient.get()
.uri("/v1/products/"+productId)
.accept(MediaType.APPLICATION_JSON)
.retrieve()
.onStatus( httpStatus -> HttpStatus.NOT_FOUND.equals(httpStatus), clientResponse -> {
Mono<NotFound> notFound = clientResponse.bodyToMono(NotFound.class);
return notFound.flatMap( msg -> {
log.info(" Error Message {}" , msg.getErrorMsg());
return Mono.error(new NotFoundException(msg.getErrorMsg()));
});
}).onStatus( httpStatus -> HttpStatus.UNAUTHORIZED.equals(httpStatus), clientResponse -> {
Mono<NotFound> notFound = clientResponse.bodyToMono(NotFound.class);
return Mono.error(new NotAuthorisedException("Unauthorised"));
}).bodyToMono(ProductResponse.class);
}

Answer 1

Two approaches:
Exceptions with webclients are all wrapped in WebClientResponseException class. You can handle that using Spring's ExceptionHandler annotation like this.
#ExceptionHandler(WebClientResponseException.class)
public ResponseEntity handleWebClientException(WebClientResponseException ex){
return ResponseEntity.badRequest().body(ex.getResponseBodyAsString());
}
Note - Here you can write complex conditional logic based on the response status, by using methods like getStatusCode(), getRawStatusCode(), getStatusText(), getHeaders() and getResponseBodyAsString(). Also you can get reference of the request that was sent using the method getRequest.
Using ExchangeFilterFunction while constructing the webclient bean.
#Bean
public WebClient buildWebClient() {
Function<ClientResponse, Mono<ClientResponse>> webclientResponseProcessor =
clientResponse -> {
HttpStatus responseStatus = clientResponse.statusCode();
if (responseStatus.is4xxClientError()) {
System.out.println("4xx error");
return Mono.error(new MyCustomClientException());
} else if (responseStatus.is5xxServerError()) {
System.out.println("5xx error");
return Mono.error(new MyCustomClientException());
}
return Mono.just(clientResponse);
};
return WebClient.builder()
.filter(ExchangeFilterFunction.ofResponseProcessor(webclientResponseProcessor)).build();
}
Then you can either handle the MyCustomClientException using #ExceptionHandler or leave it as it is.