How to Send Data in the Request Body Using HttpURLConnection in Java

How can I send data in the request body using HttpURLConnection in Java?

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("POST");
connection.setDoOutput(true);

OutputStream os = connection.getOutputStream();
byte[] input = "your data here".getBytes("utf-8");
os.write(input, 0, input.length);
os.close();

When working with HttpURLConnection in Java, sending data in the request body is integral for operations such as POST requests. This guide walks you through the steps for correctly implementing this functionality.

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

public class HttpURLConnectionExample {
    public static void main(String[] args) throws Exception {
        String urlString = "http://example.com/api";
        URL url = new URL(urlString);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);

        String jsonInputString = "{\"name\":\"John\", \"age\":30}";

        try(OutputStream os = connection.getOutputStream()) {
            byte[] input = jsonInputString.getBytes("utf-8");
            os.write(input, 0, input.length);
        }

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

Causes

• Understanding of HTTP methods (GET, POST) is needed.
• Proper demonstration of setting request headers.

Solutions

• Create a URL object pointing to the target endpoint.
• Open an HttpURLConnection instance from the URL.
• Set the request method to POST or another appropriate method.
• Enable output for the connection to send request data.
• Write the data to the connection's output stream.

Mistake: Not setting the request method to POST or another appropriate method.

Solution: Ensure you call connection.setRequestMethod("POST") before sending data.

Mistake: Missing or incorrect headers in the request.

Solution: Add necessary headers such as Content-Type if you are sending JSON data.

Mistake: Not closing the OutputStream, which might lead to memory leaks.

Solution: Use a try-with-resources statement to ensure the OutputStream is properly closed.