HTTP Status Codes - REST API Tutorial | List of HTTP status codes | HTTP Status Codes Explained

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Understanding HTTP Status Codes: A Beginner's Guide

When you browse the internet, your browser and the website's server are constantly talking to each other. Every time you click a link, the server sends back a 3-digit number called an HTTP Status Code. These codes tell us if things went well or if there was an error.

The Five Main Categories

Status codes are divided into five easy-to-remember groups based on their first digit:

• 100-199 (Informational): The server received your request and is still working on it.
• 200-299 (Success): Great news! The request was successful and everything worked.
• 300-399 (Redirection): The resource has moved, and you are being sent to a new location.
• 400-499 (Client Error): There was a mistake on your side (like a typo in the URL).
• 500-599 (Server Error): The server had a problem and couldn't complete the request.

Common Status Codes You Should Know

200 OK: This is the most common code. It means the webpage loaded perfectly!

404 Not Found: We've all seen this one. It means the page you are looking for doesn't exist on the server.

500 Internal Server Error: This is a generic "catch-all" error when the server runs into an unexpected problem.

How to See These Codes Yourself

You can actually see these codes in action! Open Google Chrome, right-click anywhere, and select "Inspect". Go to the "Network" tab and refresh the page. You will see a list of every request and its corresponding status code.

Tip for Beginners: Focus on learning the 200, 404, and 500 codes first. These will help you debug most of your basic web development problems!

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Set Response Status Code - RESTful Web Services with Spring framework | Spring Boot

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Setting Response Status Codes Effortlessly

Communication is key in any RESTful Web Service. In this tutorial, we demonstrate how to explicitly set HTTP Response Status Codes in Spring Boot using the ResponseEntity class, ensuring your API provides clear feedback to its clients.

Working with ResponseEntity

The ResponseEntity object allows you to wrap your response body and define a specific status code for every scenario. We walk through a practical example using an Employee entity and a RestController:

• Returning 200 OK: See how to return a successful status code along with the requested data when a valid ID is provided.
• Handling 400 Bad Request: Implementing logic to catch invalid inputs and return a proper error status code instead of a generic failure.
• Dynamic Logic: Learn how to use simple if-else blocks within your controller to determine the best response for the client.

Practical Demonstration

Using Postman, we test our endpoints in real-time. You'll observe how the API behaves differently when an ID is less than 10 compared to when it's 200, allowing you to see the 200 OK and 400 Bad Request responses in action within the tool.

Why This Matters

Setting specific status codes is a best practice in REST API development. It makes your backend more predictable and allows frontend clients or other services to handle results logically without parsing the entire response body. Mastering this in Spring Boot is a huge step toward building professional-grade web services.

📥 Get the Java Source Code!

The full Java source code for this tutorial is available for download! You can find the links in the YouTube video description above.