Solving the 404 Not Found Error in Your Spring Boot REST API

Learn how to troubleshoot and resolve the `404 Not Found` error in your Spring Boot REST API, ensuring your endpoints are correctly configured and accessible.
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Solving the 404 Not Found Error in Your Spring Boot REST API

As a new developer working with Spring Boot and REST APIs, encountering a 404 Not Found error can be frustrating. This error indicates that the resource you’re trying to access does not exist at the requested URL. Let’s dive into the problem, understand why it happens, and explore the solution to ensure your API works correctly.

Understanding the 404 Error

When you see a 404 Not Found error, it simply means that the server is running, but it cannot find the endpoint you’re trying to reach. This can occur due to several reasons, such as:

Incorrect URL

Missing or misconfigured annotation in your controller

The Spring application context not scanning your components correctly

Analyzing Your Current Setup

Here’s a brief overview of your existing setup, which is essential in identifying the root cause of the problem.

Project Structure

You have the following parts in your project:

Main Application Class: This is where your Spring Boot application starts.

Controller: The class that defines the REST API endpoints.

Service Layer: This layer contains the business logic.

Model Class: Represents the data structure used within your application.

Key Components

Main Class: Your main application class is named RestweekendApplication, expected to be the entry point.

Controller: A controller named ControllerProva exposes the /product endpoint.

Service Implementation: The RichiestaImpl class contains the logic to fetch the products.

Resolving the Issue

The primary reason for the 404 Not Found error in your scenario is that your Spring Boot application class might not be located correctly in the package hierarchy.

Step 1: Move the Application Class

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

Step 2: Add @RequestMapping

Make sure that your controller is correctly annotated:

The @RestController and @RequestMapping annotations are essential for defining the base path of your API. Since you have @RequestMapping("/radice") in your controller, ensure that the endpoint is correct when accessing it.

Step 3: Verify URL and Test

Once you've moved your application class to the correct package, restart the server and test the URL in your browser or via curl:

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

Additional Points to Remember

Default Scanning Behavior: The @SpringBootApplication annotation combines @Configuration, @EnableAutoConfiguration, and @ComponentScan. This means it will look for components in the package where it’s located and all sub-packages. It’s a common mistake to place the main class outside the root package.

Keep Your Structure Neat: As a best practice, always keep your main application class at the base of your package structure to avoid similar issues.

Conclusion

By moving your RestweekendApplication class to the correct package, you’ll help Spring Boot locate your components and ensure that the API endpoints become accessible. The 404 Not Found error is usually just a minor configuration issue, and with a few adjustments, you can have your Spring Boot REST API up and running smoothly.

If you encounter further issues or need clarification, don’t hesitate to reach out!