How do you implement custom exception handling in Spring MVC?

Table of Contents

• Introduction
• Implementing Custom Exception Handling in Spring MVC
  • 1. Creating Custom Exception Classes
    • Example: Defining Custom Exception Classes
  • 2. Using @ControllerAdvice for Global Exception Handling
    • Example: Global Exception Handling with @ControllerAdvice
  • 3. Returning Custom Error Responses in REST APIs
    • Example: Handling Exceptions in a RESTful API
  • 4. Customizing Error Views
    • Example: Custom Error Views
  • 5. Returning HTTP Status Codes with Custom Error Pages
    • For Spring Boot:
  • 6. Handling Validation Errors
    • Example: Handling Validation Errors
  • Conclusion

Introduction

In any application, error handling is a crucial part of ensuring a good user experience and maintaining the application's integrity. In Spring MVC, you can handle exceptions in a variety of ways, from handling specific exceptions in controller methods to global exception handling across the entire application. Implementing custom exception handling allows you to centralize error responses, offer detailed error messages, and return appropriate HTTP status codes.

In this guide, we'll explore how to implement custom exception handling in Spring MVC using @ControllerAdvice, custom exception classes, and error response handling. Whether you're building a RESTful API or a web application, these techniques will help you manage errors effectively and provide meaningful feedback to users.

Implementing Custom Exception Handling in Spring MVC

1. Creating Custom Exception Classes

Before handling exceptions, you'll typically create custom exception classes that represent specific error conditions in your application. These classes extend Java's Exception or RuntimeException classes and can be annotated with @ResponseStatus for automatic mapping of status codes.

Example: Defining Custom Exception Classes

In this example:

• ResourceNotFoundException is annotated with @ResponseStatus, which automatically maps this exception to a 404 status code when thrown.
• InvalidInputException is mapped to a 400 status code for invalid input.

Custom exceptions like these allow for more specific error handling and a more meaningful response to the client.

2. Using @ControllerAdvice for Global Exception Handling

Spring provides @ControllerAdvice to handle exceptions globally across your entire application. @ControllerAdvice works with @ExceptionHandler to catch exceptions thrown by any controller method and return a customized response (like a view or a JSON response).

Example: Global Exception Handling with @ControllerAdvice

In this example:

• @ControllerAdvice is used to globally catch exceptions thrown from any controller method.
• The @ExceptionHandler annotation maps specific exceptions (like ResourceNotFoundException and InvalidInputException) to corresponding error views (error/404, error/400).
• A generic Exception.class handler is used to catch all other exceptions and return a generic error page (error/500).

3. Returning Custom Error Responses in REST APIs

For RESTful APIs, it’s common to return error details in a structured format like JSON. Instead of rendering a view, you can return an error message or error code in the response body.

Example: Handling Exceptions in a RESTful API

In this example:

• @ControllerAdvice is used to catch exceptions globally for the REST API.
• When ResourceNotFoundException is thrown, a 404 Not Found response with a JSON body is returned, containing the error message.
• ErrorResponse is a custom class that represents the error structure in the response body.

When an exception is thrown, this approach ensures the client receives a structured, JSON-based error response.

4. Customizing Error Views

If you prefer to show custom error pages for different HTTP errors (like 404 or 500), you can create custom error view templates and configure them to be displayed when specific exceptions are caught.

Example: Custom Error Views

For JSP or Thymeleaf views:

• 404.jsp or 404.html could be used to display a "Page Not Found" error when a ResourceNotFoundException is thrown.
• 500.jsp or 500.html could be used to show a "Server Error" message for any other exceptions.

In the @ControllerAdvice example above, you can return these custom views as follows:

5. Returning HTTP Status Codes with Custom Error Pages

In some cases, you may want to map specific HTTP status codes (like 404 or 500) to custom error pages using web.xml or Spring Boot's configuration files.

For Spring Boot:

Then, create a controller method to handle the /error path:

6. Handling Validation Errors

If you're using Spring's @Valid annotation for input validation, you can use @ControllerAdvice to handle validation errors globally.

Example: Handling Validation Errors

Conclusion

Custom exception handling in Spring MVC enhances the robustness and user-friendliness of your application by centralizing error management, improving error responses, and allowing you to return appropriate HTTP status codes and messages. By using @ControllerAdvice, custom exceptions, and error view templates, you can create a well-organized and maintainable error-handling mechanism that works for both web applications and REST APIs. Implementing global exception handling ensures that your Spring application can gracefully handle a variety of error conditions, providing meaningful feedback to users while avoiding repetitive code across multiple controller methods.