Скачать или смотреть How to Fix the Bad Request Error and Return a Not Found Status in Spring Boot

Learn how to correctly handle exceptions in Spring Boot to return the appropriate `404 Not Found` status instead of the `400 Bad Request` response.
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This video is based on the question https://stackoverflow.com/q/63815810/ asked by the user 'Alexei' ( https://stackoverflow.com/u/6813231/ ) and on the answer https://stackoverflow.com/a/63818238/ provided by the user 'Nakul Goyal' ( https://stackoverflow.com/u/13127098/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When building applications using Spring Boot, handling HTTP responses correctly is crucial for providing a seamless user experience. A frequent issue developers encounter is returning an unexpected 400 Bad Request status when they intend to send back a 404 Not Found status for a missing resource. This guide will explain why this issue occurs and how to resolve it effectively.

Problem: Receiving a 400 Bad Request Instead of a 404 Not Found

You may encounter a situation where you throw an exception in your controller, expecting a 404 Not Found response to inform the user of the missing resource. However, instead, you receive a 400 Bad Request response. This can confuse users and make debugging more complicated.

Example Scenario

In your Spring Boot application, the following logic is in place for updating a product:

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When the ProductNotFoundException is thrown, instead of getting a 404, you see the following in your HTTP response:

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This indicates a Bad Request error when you were expecting Not Found.

Solution: Properly Handle Exceptions in Spring Boot

To resolve this issue, you can utilize @ RestControllerAdvice or @ ControllerAdvice to create a global exception handler for your application. This way, you define how your application should respond when specific exceptions are thrown.

Step-by-Step Implementation

Define a Custom Exception Handler

Create a new class that will handle exceptions globally. Here’s an example of how you can implement this:

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Explanation of the Code

@ RestControllerAdvice: This annotation marks this class as a global exception handler for controllers using REST. It allows you to handle exceptions thrown by any REST controller in your application.

@ ExceptionHandler(ProductNotFoundException.class): This method will be called whenever a ProductNotFoundException is thrown.

@ ResponseStatus(HttpStatus.NOT_FOUND): Specifies that the response should be 404 Not Found when this exception is triggered.

ResponseMsg: This is a custom class that packages the error message to return as a JSON response.

Benefits of This Approach

Clean Separation of Concerns: Keeps your controller logic clean and focused on handling requests and responses while error handling is managed separately.

Reusability: You can define multiple exception handling methods for different exception types within the same advice class, promoting code reusability.

Improved User Experience: Users receive more informative and precise responses when errors occur, enhancing overall application usability.

Conclusion

Understanding how to effectively manage exception responses in Spring Boot is essential for creating robust applications. By utilizing @ RestControllerAdvice or @ ControllerAdvice, you can ensure that your application responds with the appropriate HTTP status codes, such as 404 Not Found instead of 400 Bad Request. This will not only improve the reliability of your application but also provide a better experience for users.

Feel free to reach out in the comments if you have any further questions or if there's anything else you'd like us to cover!