How do you implement exception handling for REST APIs in Spring Boot?

Table of Contents

Introduction

Exception handling is a crucial part of developing RESTful APIs in Spring Boot. It ensures that when something goes wrong, the API responds with meaningful and consistent error messages, rather than exposing internal details of the application. Spring Boot offers several ways to implement robust exception handling mechanisms for your REST APIs. In this guide, we'll cover how to handle exceptions effectively using @ControllerAdvice, custom exceptions, and ResponseEntity.

Methods to Implement Exception Handling in Spring Boot

1. Using @ControllerAdvice for Global Exception Handling

@ControllerAdvice is a specialized annotation in Spring that allows you to handle exceptions globally across all controllers in your Spring Boot application. It is used to define global exception handling logic and is especially useful when building RESTful APIs.

Example of Global Exception Handling with @ControllerAdvice:

In this example:

  • @ExceptionHandler is used to handle exceptions.
  • ResourceNotFoundException is a custom exception, and when it occurs, a detailed error response is sent with HTTP status 404 NOT_FOUND.
  • A generic exception handler catches all other exceptions and returns a 500 INTERNAL_SERVER_ERROR status.

Error Response Class:

The ErrorResponse class is used to structure the error messages returned to the client in a consistent format.

2. Creating Custom Exception Classes

In a real-world application, you often need to create custom exceptions that represent specific error scenarios. For instance, if a user tries to access a non-existing resource, you can throw a custom exception like ResourceNotFoundException.

Example of a Custom Exception:

You can throw this exception in your controller or service layer to indicate that a resource was not found.

If the product is not found, the ResourceNotFoundException will be thrown and handled by the global exception handler defined with @ControllerAdvice.

3. Handling Validation Errors with @Valid and BindingResult

When dealing with input validation, Spring Boot provides built-in support to catch validation errors automatically. You can use @Valid along with BindingResult to handle input validation exceptions in a REST API.

Example with Validation:

In this example, if validation fails (for example, missing required fields or invalid values), an exception like ValidationException will be thrown.

Handling Validation Exception:

4. Using ResponseEntity for Custom Error Responses

In Spring Boot, ResponseEntity is a flexible way to build HTTP responses, including error responses. This allows you to return custom HTTP status codes and body content along with your error messages.

Example with ResponseEntity:

Here, the ResponseEntity is used to return a custom error response with the HTTP status 404 NOT FOUND and a JSON body with an error code and message.

Practical Example of Exception Handling in REST APIs

Let’s put it all together in a simple Spring Boot application.

Controller Example:

Global Exception Handler Example:

Resulting Error Response:

If a GET request is made to /products/9999 (where the product does not exist), the response will be:

Conclusion

Exception handling in Spring Boot for REST APIs is essential for building reliable and user-friendly services. By using @ControllerAdvice, custom exception classes, and ResponseEntity, you can manage errors globally and return structured, meaningful error messages to clients. This ensures that your application is both resilient to errors and provides clear communication when something goes wrong. Exception handling also plays a critical role in maintaining the overall quality and stability of your RESTful APIs.

Share
Similar Questions