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Discover how to create custom exceptions in Spring Boot that provide meaningful error messages to your users using `@ ControllerAdvice`.
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How to Display Descriptive Spring Boot Exceptions Using @ ControllerAdvice

When building applications with Spring Boot, you might encounter scenarios where exceptions are not very informative. For instance, if your application throws a 404 Not Found error, the default error message might not provide any details about the issue, leaving users confused.

In this guide, we will tackle the problem of displaying descriptive exceptions in your Spring Boot application, specifically using a custom exception class. We'll also explore the use of @ ControllerAdvice to enhance error handling across the application.

The Problem

Imagine you are developing a RESTful API that serves dog breeds based on a unique identifier. If a user tries to access a dog breed that does not exist, the application may throw a generic 404 error like the following:

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From this response, it's unclear what the actual issue is — did the user enter an incorrect ID? Was there a problem with the database? Such generic responses are not helpful for debugging or user experience.

The Existing Code

In your Spring Boot application, you might have a service method like this:

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In this code, if the dog breed with the given ID is not found, it throws a custom exception called DogNotFoundException:

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While you intended to return the message "Dog not found", the response still lacks contextual information.

The Solution: Utilizing @ ControllerAdvice

To provide users with more meaningful error messages, we can implement a global error handling mechanism using @ ControllerAdvice. This allows us to catch exceptions thrown by any controller across the application.

Step-by-Step Implementation

Create a Exception Handler Class: We will create a class annotated with @ ControllerAdvice.

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Handle the Custom Exception: In the handleDogNotFoundException method, we specify how to respond when a DogNotFoundException is thrown. We create a response body containing:

A descriptive message

A timestamp of when the error occurred

Return a Meaningful Response: Instead of a generic error page, the user will now receive a structured response like:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing a global exception handler using @ ControllerAdvice, we've drastically improved how errors are communicated in a Spring Boot application. Not only does this provide better context for developers debugging issues, but it also enhances user experience by clearly communicating what went wrong.

Next time you need to handle exceptions in your Spring Boot application, consider using @ ControllerAdvice to ensure your users receive informative error messages.

For further enhancements, you might also want to explore logging the exceptions or adding more details to your error responses. Happy coding!