apache httpclient user authentication

Apache HttpClient provides support for various types of user authentication, including Basic Authentication, Digest Authentication, NTLM Authentication, and Kerberos Authentication. Here's an example that demonstrates how to use Basic Authentication with Apache HttpClient:

import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpClientExample {
    public static void main(String[] args) throws Exception {
        String username = "myusername";
        String password = "mypassword";

        CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY,
            new UsernamePasswordCredentials(username, password));

        HttpClient httpClient = HttpClientBuilder.create()
            .setDefaultCredentialsProvider(credentialsProvider)
            .build();

        HttpGet httpGet = new HttpGet("http://www.example.com");
        String responseBody = EntityUtils.toString(httpClient.execute(httpGet).getEntity());
        System.out.println(responseBody);
    }
}

In this example, we first create an instance of CredentialsProvider that stores the user credentials, and set it to use Basic Authentication by default. We then create an instance of HttpClient using the HttpClientBuilder class, and set the CredentialsProvider on it using the setDefaultCredentialsProvider() method. Finally, we execute an HTTP GET request using the HttpClient object, and extract the response body using the EntityUtils class.

Note that this example demonstrates how to use Basic Authentication with a single username and password. For more complex authentication scenarios, such as using different credentials for different URLs or realms, you may need to use more advanced authentication techniques, such as Digest Authentication or NTLM Authentication. You can find more information about these techniques in the Apache HttpClient documentation.