Java HttpURLConnection Class

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The java.net package contains URLConnection as an abstract class which creates a communication link between a Java application and a URL. This class enables operations to read data from the URL resource and write data to it.

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This class enables users to download data and upload files while interacting with HTTP APIs using its HttpURLConnection subclass.

Syntax

Import Statements

import java.net.HttpURLConnection;
import java.net.URL;
import java.io.*;

Creating a Connection

URL url = new URL("https://api.example.com/data");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();

Methods of HttpURLConnection

Method Description
setRequestMethod(String method) Sets HTTP method (GET, POST, etc.)
getInputStream() Reads response from server
getOutputStream() Sends data to server
setDoOutput(boolean) Enables output (for POST/PUT)
setRequestProperty(String key, String value) Adds headers (e.g., Content-Type)
getResponseCode() Returns HTTP status code
disconnect() Closes connection

Example

HTTP GET Request

 public class HttpGetExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://api.github.com");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");

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

        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String inputLine;
        StringBuilder content = new StringBuilder();
        while ((inputLine = in.readLine()) != null) {
            content.append(inputLine);
        }
        in.close();
        conn.disconnect();

        System.out.println("Response:\n" + content);
    }
}

Example

HTTP POST Request

public class HttpPostExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://httpbin.org/post");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();

        conn.setRequestMethod("POST");
        conn.setDoOutput(true); // Enable output for POST
        conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

        String postData = "username=javauser&password=secret";

        try (OutputStream os = conn.getOutputStream()) {
            os.write(postData.getBytes());
            os.flush();
        }

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

        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String inputLine;
        StringBuilder response = new StringBuilder();

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();

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