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Discover how to create a `Spring Boot REST API` with Java while troubleshooting common issues such as the 404 Not Found error. Learn effective solutions and best practices in this comprehensive guide.
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This video is based on the question https://stackoverflow.com/q/74087719/ asked by the user 'Khaled El Attar' ( https://stackoverflow.com/u/15189779/ ) and on the answer https://stackoverflow.com/a/74087862/ provided by the user 'Neos' ( https://stackoverflow.com/u/19972444/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Build a Spring Boot REST API with Java: Troubleshooting Common Issues

Creating a REST API using Spring Boot and Java can be a rewarding experience, allowing developers to create robust web services. However, you may encounter obstacles along the way, such as the frustrating 404 Not Found error when sending requests to your API endpoints. In this guide, we will cover how to build a Spring Boot REST API using Java and provide solutions to common issues that can arise during development.

The Problem: Encountering a 404 Not Found Error

Picture this: you've spent hours building your Spring Boot application, only to receive a 404 Not Found response when you try to access your API. For example, when you send a request to http://localhost:8082/api/user through Postman, the response returns 404. This issue commonly arises due to reasons such as incorrect URL mapping or missing context paths in the configuration.

Common Misconfigurations

Incorrect URL Mapping: Ensure that you are using the correct endpoint in your API requests based on your controller's setup.

Request Path Issues: If your application is set to a specific context path, you may need to adjust your endpoint accordingly.

Understanding Your Application Configuration

Let’s break down the configuration and code snippets provided in the question for clarity.

1. Configuration Properties

The application.properties file plays a vital role in configuring your Spring Boot application. Below is an overview of important properties set in the file:

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These settings configure your database connection and specify the server's port. Ensure that the database credentials are correct and that the MySQL database is running.

2. User Model

The User entity represents the user data structure in your application:

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This entity class is well defined, but it’s important to ensure that your database table matches this structure.

3. Repository Interface

The UserRepository interface is responsible for database operations:

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This code snippet is straightforward and correctly leverages Spring Data JPA.

4. Controller Definition

The controller is where you define endpoints for your API:

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Rectifying the 404 Not Found Error

Solutions to Common Issues

Add Valid ID in URL: When calling GET /api/user/{id}, ensure that you replace {id} with an actual user ID that exists in the database. For example, use http://localhost:8082/api/user/1 if a user with ID 1 exists.

Adjust Request Mapping: If you encounter extra context paths, consider changing the controller's request mapping to possibly simplify the URL:

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

Check Context Path Configuration: If you are using Spring Boot 2.x or higher, ensure proper context path is configured in your application properties:

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

Conclusion

Building a Spring Boot REST API can be an enriching task, but as with all development, challenges may arise. By ensuring your URL mappings are correct and that you are following best practices in your configurations, you can effectively troubleshoot and overcome the common 404 Not Found errors.

Happy coding, and may your Spring Boot journey be a smooth one!