Error Handling | Spring Webflux | Spring Framework Tutorial

Introduction

Error handling is a crucial aspect of any web application. In Spring WebFlux, which is a reactive programming framework, managing errors can be significantly different from traditional servlet-based applications. Understanding how to handle errors effectively ensures that your application remains robust and user-friendly.

Types of Errors in WebFlux

In Spring WebFlux, you can encounter various types of errors:

Runtime Exceptions: These are exceptions that occur during the execution of the application.
Client Errors: Errors related to client requests, like 404 Not Found.
Server Errors: Errors occurring on the server side, such as 500 Internal Server Error.

Global Error Handling

Global error handling in Spring WebFlux can be implemented using the @ControllerAdvice annotation. This allows you to define a centralized error handling mechanism for your application.

Example: Global Error Handler

Below is an example of a global error handler.

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(RuntimeException.class)
    public ResponseEntity handleRuntimeException(RuntimeException ex) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
                             .body("An error occurred: " + ex.getMessage());
    }
}

Handling Errors in Controllers

You can also handle errors directly within your controllers. This approach can be useful for handling specific types of exceptions that occur within the controller's scope.

Example: Controller-Level Error Handling

Here’s how you might handle errors within a specific controller.

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    @GetMapping("/data")
    public ResponseEntity getData() {
        if (someConditionThatCausesError) {
            throw new RuntimeException("Data not found");
        }
        return ResponseEntity.ok("Here is your data");
    }
}

Exception Handling with WebFlux

Spring WebFlux also provides specialized exception handling methods using the onErrorResume and doOnError operators. These can be used to manage errors in a reactive style.

Example: Using onErrorResume

Here’s an example of handling errors using onErrorResume.

import reactor.core.publisher.Mono;

public Mono findData() {
    return someReactiveSource()
        .onErrorResume(ex -> {
            return Mono.just("Default Data");
        });
}

Conclusion

Effective error handling in Spring WebFlux is essential for building resilient applications. By leveraging global exception handlers, controller-level error handling, and reactive error management techniques, you can ensure your application responds gracefully to errors and provides meaningful feedback to users.

Error Handling in Spring WebFlux