How do you return custom error responses in Spring Boot?

Table of Contents

Introduction

In Spring Boot, providing custom error responses is essential for building a robust, user-friendly API. Rather than relying on the default error messages that Spring generates, you can define your own error structure to convey meaningful information to clients. Custom error responses allow you to return consistent and clear feedback, which can include custom error codes, messages, and additional data about the error.

In this guide, we will cover how to create and return custom error responses in Spring Boot using @ExceptionHandler, ResponseEntity, and other tools for structured error handling in your REST APIs.

Methods for Returning Custom Error Responses in Spring Boot

1. Using **@ExceptionHandler** to Return Custom Error Responses

The @ExceptionHandler annotation is a powerful way to handle exceptions in Spring Boot and return custom error responses. You can use @ExceptionHandler inside a controller or globally with @ControllerAdvice to catch exceptions and return a structured response.

Example: Custom Error Response in @ExceptionHandler

In this example:

  • The ProductNotFoundException is thrown when a product is not found by its ID.
  • The @ExceptionHandler method captures the exception and returns a custom error response with the HTTP status 404 NOT_FOUND.

Error Response Class:

The ErrorResponse class is used to structure the custom error message, including an error code and a human-readable message.

2. Global Exception Handling with **@ControllerAdvice**

To handle exceptions globally across all controllers in your Spring Boot application, you can use @ControllerAdvice. This approach avoids code duplication by centralizing exception handling logic in one place.

Example: Global Exception Handling with @ControllerAdvice

In this example:

  • All ProductNotFoundException instances are caught globally and handled with a custom error response.
  • A generic Exception handler is also included to handle unexpected errors globally.

3. Using **ResponseEntity** for Custom Error Responses

Spring Boot allows you to use ResponseEntity to return customized HTTP responses, including status codes, headers, and body content. ResponseEntity is ideal for crafting custom error responses because it provides flexibility to specify both the HTTP status and the response body.

Example: Returning a Custom Error Response with ResponseEntity

In this case:

  • A ResponseEntity is used to wrap the ErrorResponse object and return it with an HTTP status of 404 NOT_FOUND.
  • ResponseEntity ensures that you can not only send the custom error response body but also set headers or other HTTP parameters if needed.

4. Returning Validation Errors with **BindingResult**

In scenarios where input validation fails, Spring provides an easy way to return validation error details. You can use the BindingResult to capture validation errors and create a custom error response.

Example: Handling Validation Errors

In this example:

  • The @Valid annotation ensures that the product is validated before being passed to the controller method.
  • If there are validation errors, a ValidationException is thrown, and a custom error response is returned to the client.

Example: Handling Validation Exception

5. Customizing the Error Response Format

You can also customize the structure of the error response to include additional information, such as timestamps or detailed error descriptions.

Example: Enhanced Error Response

In this enhanced version of ErrorResponse:

  • details can provide more information about the error.
  • timestamp allows you to include the time when the error occurred.

You can modify your @ExceptionHandler methods to use this enhanced response format.

Practical Example of Returning Custom Error Responses

Let’s walk through a practical example of a ProductController with custom error responses.

ProductController:

GlobalExceptionHandler with Enhanced ErrorResponse:

Example Response (when an error occurs):

Conclusion

In Spring Boot, returning custom error responses enhances the user experience by providing meaningful feedback and ensuring consistency across your API. Using @ExceptionHandler for exception handling, ResponseEntity for customizing responses, and creating structured ErrorResponse classes gives you complete control over how errors are communicated to clients. By leveraging these tools, you can build a more reliable and maintainable REST API with clear and actionable error messages.

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