Global Exception handling in Spring reactor and dependent responses - spring

Question

I am trying to create a web application using spring 5 . It's a micro-service which hit few other micro-services. Response from one service is dependent the other.I am using global exception handing in my application.
Here is my code:
#Override
public Mono<Response> checkAvailablity(Request request) {
Mono<Response> authResponse = userService.authenticateToken(request);
return authResponse.doOnSuccess(t -> {
// if success is returned.
// Want to return this innerResponse
Mono<Response> innerResponse =
httpService.sendRequest(Constant.SER_BOOKING_SERVICE_CHECK_AVAILABILTY,
request.toString(), Response.class);
}).doOnError(t -> {
logger.info("Subscribing mono in Booking service - On Error");
Mono.error(new CustomException(Constant.EX_MODULE_CONNECTION_TIMED_OUT));
});
In case of error I want to throw CustomException and catch it in global exception handler:
#ControllerAdvice
public class ExceptionInterceptor {
public static Logger logger = Logger.getLogger(ExceptionInterceptor.class);
#ExceptionHandler(value = CustomException.class)
#ResponseBody
public Response authenticationFailure(ServerHttpRequest httpRequest, ServerHttpResponse response,
CustomException ex) {
logger.info("CustomException Occured with code => " + ex.getMessage());
return buildErrorResponse(ex.getMessage());
}
Based on the above code I have two problems:
The exception which is thrown in Mono.error() is not captured in global exception handler.
In case of success, response from the inner service should be returned.

Answer 1

Used two methods in mono: flatmap() and onErrorMap()
and updated my checkAvailablity() code:
public Mono<Response> checkAvailablity(Request request) {
Mono<Response> authResponse = userService.authenticateToken(request);
return authResponse.flatmap(t -> {
// Added transform() for success case
Mono<Response> response = httpService.sendRequest(Constant.SER_BOOKING_SERVICE_CHECK_AVAILABILTY,
request.toString(), Response.class);
logger.info("Response from SER_BOOKING_SERVICE_CHECK_AVAILABILTY");
return response;
}).onErrorMap(t -> {
// Added onErrorMap() for failure case & now exception is caught in global exception handler.
throw new CustomException(Constant.EX_MODULE_CONNECTION_TIMED_OUT);
});
}