What is HttpURLConnection?

#httpurlconnection #java

HttpURLConnection is a class in Java used to send HTTP requests and receive responses from web servers. It belongs to the java.net package and is commonly used to interact with REST APIs and web services.

📌 Why Do We Use HttpURLConnection?

To call REST APIs 🌐
To send GET, POST, PUT, DELETE requests
To fetch data from web servers
To integrate external services (payment APIs, weather APIs, etc.)

📌 How HttpURLConnection Works

Create a URL
Open connection
Set request method (GET/POST)
Send request
Read response

🔹 Example: HTTP GET Request

java id="h3k92l"
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://jsonplaceholder.typicode.com/posts/1");
        HttpURLConnection con = (HttpURLConnection) url.openConnection();

        con.setRequestMethod("GET");

        int status = con.getResponseCode();
        System.out.println("Response Code: " + status);

        BufferedReader br = new BufferedReader(
                new InputStreamReader(con.getInputStream()));

        String line;
        StringBuilder response = new StringBuilder();

        while ((line = br.readLine()) != null) {
            response.append(line);
        }
        br.close();

        System.out.println("Response: " + response.toString());
    }
}

🔹 Example: HTTP POST Request

java id="o9w2ks"
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class PostExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://jsonplaceholder.typicode.com/posts");
        HttpURLConnection con = (HttpURLConnection) url.openConnection();

        con.setRequestMethod("POST");
        con.setDoOutput(true);

        String jsonInput = "{\"title\":\"Java\",\"body\":\"Learning\",\"userId\":1}";

        OutputStream os = con.getOutputStream();
        os.write(jsonInput.getBytes());
        os.flush();
        os.close();

        int responseCode = con.getResponseCode();
        System.out.println("POST Response Code: " + responseCode);
    }
}

🚀 Important Methods

Method	Description
`setRequestMethod()`	Sets HTTP method (GET, POST, etc.)
`getResponseCode()`	Returns HTTP status code
`getInputStream()`	Reads response data
`getOutputStream()`	Sends request data
`setDoOutput(true)`	Enables sending data

🔥 Advantages

Built-in Java API (no external libraries needed)
Supports HTTP & HTTPS
Useful for API integration
Fine control over request/response

⚠️ Limitations

Verbose and complex code
Harder to manage compared to modern libraries
No automatic JSON parsing

👉 In real-world projects, developers often use libraries like:

Apache HttpClient
OkHttp
Spring RestTemplate / WebClient

🎯 Real-Time Use Cases

Calling REST APIs
Fetching weather/news data
Payment gateway integration
Microservices communication

✅ Conclusion

HttpURLConnection is a core Java class for handling HTTP communication. While it may seem a bit complex, it gives you full control over network requests and is widely used in backend systems.

Learning this concept is crucial if you're preparing for real-time projects and interviews through Top Core JAVA Online Training in Hyderabad.

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