Resolving the 404 Error in Spring Boot Controllers: A Guide to Correct API Mapping

Discover how to resolve the common `404 error` encountered in Spring Boot when the controller is recognized but the API isn’t mapped. Follow our guide for quick troubleshooting tips!
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Resolving the 404 Error in Spring Boot Controllers: A Guide to Correct API Mapping

When developing an application using Spring Boot, encountering a 404 Not Found error can be frustrating, especially when you see that your controller is recognized but the API is not bound correctly. This issue generally arises from misconfigured package scanning or missing dependencies. In this guide, we’ll guide you through the process of diagnosing and resolving this common problem.

Understanding the Issue

Symptoms of the Problem

Before jumping into the solution, let’s recap the symptoms that indicate something is wrong:

You have a visible output in the logs indicating that the controller is being detected (i.e., “Identified candidate component class”).

When accessing the endpoint, you receive a 404 error instead of the expected response.

Steps to Resolve the 404 Error

Let’s break down the solution into manageable steps to ensure that your Spring Boot application can correctly handle requests to your API.

1. Verify Package Scanning

By default, Spring Boot scans the package of the main application class and its sub-packages. However, if your controller resides in a different package structure, you’ll need to specify the package explicitly. You can do this by annotating your main class with @SpringBootApplication and using the scanBasePackages attribute:

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This change ensures that Spring scans all specified packages for components, including your controller.

2. Ensure the Correct Dependency is Included

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This dependency is crucial as it includes all the necessary components for building web applications with Spring Boot.

3. Double-check the Controller Mapping

Finally, review your controller mapping to ensure it is set up correctly. In your case, check that you have the following annotation in your controller class:

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Make sure that your endpoint is indeed /util as you intend to access it. Since the application is also set to have a context path (/util-service), the full URI to access your endpoint should be constructed accordingly.

Testing the Fix

Once you incorporate the changes specified, restart your application and try accessing:

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If everything is configured correctly, you should see the expected response instead of the $404 error.

Conclusion

Encountering a 404 Not Found error in your Spring Boot application can be a result of several configuration issues, primarily related to package scanning and dependencies. By following the structured approach outlined above, you can pinpoint and resolve the issue efficiently. Always remember to ensure that your package structures and context paths are aligned, and check your dependencies for your web application.

If you continue to face issues, dive deeper into the logs for more insights, and don’t hesitate to reach out to the development communit