How to pass an Authentication Header Token when POSTing data to an API in Java

A guide on how to pass an authentication token in the Authorization Header when sending POST requests to an API using Java. The article provides sample Java code and detailed explanations.

In this article, we will explore how to send an authentication token in the Authorization Header when performing a POST request to an API using Java. This method is commonly used in secure applications to authenticate users or applications.

Java Code:

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

public class ApiRequestWithToken {
    public static void main(String[] args) {
        try {
            // Set the API URL
            URL url = new URL("https://api.example.com/data");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            // Set the request method to POST
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/json");

            // Add Authentication Token to the Header
            String token = "your-authentication-token";
            conn.setRequestProperty("Authorization", "Bearer " + token);

            // Enable output to send POST data
            conn.setDoOutput(true);

            // The JSON data to be sent
            String jsonInputString = "{\"key1\": \"value1\", \"key2\": \"value2\"}";

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

            // Check the response code
            int responseCode = conn.getResponseCode();
            System.out.println("Response Code: " + responseCode);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Detailed explanation:

1. URL url = new URL("https://api.example.com/data");: Creates a URL pointing to the API to which the POST request will be sent.
2. HttpURLConnection conn = (HttpURLConnection) url.openConnection();: Opens an HTTP connection to the URL.
3. conn.setRequestMethod("POST");: Sets the request method to POST.
4. conn.setRequestProperty("Content-Type", "application/json");: Specifies the content type as JSON.
5. conn.setRequestProperty("Authorization", "Bearer " + token);: Adds the token to the Authorization header in the "Bearer" format.
6. conn.setDoOutput(true);: Enables the connection to send data in the POST request.
7. String jsonInputString = "{\"key1\": \"value1\", \"key2\": \"value2\"}";: JSON data to be sent to the API.
8. try (OutputStream os = conn.getOutputStream()) { ... }: Writes the JSON data to the connection.
9. int responseCode = conn.getResponseCode();: Retrieves the server's response code and prints the result.

System requirements:

• Java version 8 or higher.
• Internet connection and API access.

How to install the libraries needed to run the above code:

• This Java code uses standard libraries, no external libraries are required.

Tips:

• It’s important to encrypt and securely handle tokens before sending them in a real-world application.
• Carefully inspect the API response to handle errors or unexpected information.

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