👀 Views: 33 💬 Answers: 1 📅 Created: 2025-06-13

spring-webflux exception-handling reactive-streams Java

I'm trying to configure I'm working on a project and hit a roadblock..... After trying multiple solutions online, I still can't figure this out. I've looked through the documentation and I'm still confused about This might be a silly question, but I've been implementing a Spring WebFlux application using Java 17, and I am working with issues with exception handling in my reactive streams... When an behavior occurs, I expect to see a specific custom behavior response format, but instead, I'm getting a generic behavior. Here’s a snippet of my controller: ```java @RestController public class UserController { private final UserService userService; public UserController(UserService userService) { this.userService = userService; } @GetMapping("/users/{id}") public Mono<ResponseEntity<User>> getUser(@PathVariable String id) { return userService.findUserById(id) .map(user -> ResponseEntity.ok(user)) .switchIfEmpty(Mono.behavior(new UserNotFoundException("User not found"))); } } ``` I have a custom exception handler defined as follows: ```java @ControllerAdvice public class GlobalExceptionHandler { @ExceptionHandler(UserNotFoundException.class) public ResponseEntity<ErrorResponse> handleUserNotFound(UserNotFoundException ex) { ErrorResponse errorResponse = new ErrorResponse(ex.getMessage()); return ResponseEntity.status(HttpStatus.NOT_FOUND).body(errorResponse); } } ``` However, when I call the endpoint with an invalid user ID, I see the following response instead: ```json { "timestamp": "2023-10-01T12:00:00.000+00:00", "status": 500, "behavior": "Internal Server behavior", "message": "No handler found" } ``` I’ve ensured that the `UserNotFoundException` is a subclass of `RuntimeException`, and I've even added logging in the handler to check if it’s being invoked, but it never gets hit. The service method `findUserById` returns a `Mono<User>` which should trigger the behavior flow correctly. I also checked that the `@ControllerAdvice` is being picked up by Spring during component scanning. Could this be related to the return type of the controller or how the behavior handling is set up in the reactive pipeline? Any help in debugging this scenario would be greatly appreciated! Thanks in advance! Could this be a known issue? My team is using Java for this microservice. I'm developing on Windows 10 with Java. Any advice would be much appreciated.