Apache HttpClient - 代理认证

本章节将学习如何创建一个使用用户名和密码进行身份验证的 HttpRequest，并通过代理将其传输到目标主机，并通过示例进行说明。

步骤 1 - 创建 CredentialsProvider 对象

CredentialsProvider 接口维护一个集合来保存用户登录凭据。您可以通过实例化 BasicCredentialsProvider 类（此接口的默认实现）来创建其对象。

CredentialsProvider credentialsPovider = new BasicCredentialsProvider();

步骤 2 - 设置凭据

您可以使用 **setCredentials()** 方法将所需的凭据设置为 CredentialsProvider 对象。此方法接受两个对象：

**AuthScope 对象** - 身份验证范围，指定主机名、端口号和身份验证方案名称等详细信息。
**Credentials 对象** - 指定凭据（用户名、密码）。如下所示，使用 **setCredentials()** 方法为主机和代理设置凭据。

credsProvider.setCredentials(new AuthScope("example.com", 80), new
   UsernamePasswordCredentials("user", "mypass"));
credsProvider.setCredentials(new AuthScope("localhost", 8000), new
   UsernamePasswordCredentials("abc", "passwd"));

步骤 3 - 创建 HttpClientBuilder 对象

如下所示，使用 **HttpClients** 类的 **custom()** 方法创建一个 **HttpClientBuilder**：

//Creating the HttpClientBuilder
HttpClientBuilder clientbuilder = HttpClients.custom();

步骤 4 - 设置 CredentialsProvider

您可以使用 **setDefaultCredentialsProvider()** 方法将 CredentialsProvider 对象设置为 HttpClientBuilder 对象。将前面创建的 **CredentialsProvider** 对象传递给此方法。

clientbuilder = clientbuilder.setDefaultCredentialsProvider(credsProvider);

步骤 5 - 构建 CloseableHttpClient

使用 **build()** 方法构建 **CloseableHttpClient** 对象。

CloseableHttpClient httpclient = clientbuilder.build();

步骤 6 - 创建代理和目标主机

通过实例化 **HttpHost** 类来创建目标和代理主机。

//Creating the target and proxy hosts
HttpHost target = new HttpHost("example.com", 80, "http");
HttpHost proxy = new HttpHost("localhost", 8000, "http");

步骤 7 - 设置代理并构建 RequestConfig 对象

使用 **custom()** 方法创建一个 **RequestConfig.Builder** 对象。使用 **setProxy()** 方法将前面创建的 proxyHost 对象设置为 **RequestConfig.Builder**。最后，使用 **build()** 方法构建 **RequestConfig** 对象。

RequestConfig.Builder reqconfigconbuilder= RequestConfig.custom();
reqconfigconbuilder = reqconfigconbuilder.setProxy(proxyHost);
RequestConfig config = reqconfigconbuilder.build();

步骤 8 - 创建 HttpGet 请求对象并将其配置对象设置到其中。

通过实例化 HttpGet 类来创建一个 **HttpGet** 对象。使用 **setConfig()** 方法将上一步中创建的配置对象设置为此对象。

//Create the HttpGet request object
HttpGet httpGet = new HttpGet("/");

//Setting the config to the request
httpget.setConfig(config);

步骤 9 - 执行请求

通过将 HttpHost 对象（目标）和请求（HttpGet）作为参数传递给 **execute()** 方法来执行请求。

HttpResponse httpResponse = httpclient.execute(targetHost, httpget);

示例

以下示例演示如何使用用户名和密码通过代理执行 HTTP 请求。

import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;

public class ProxyAuthenticationExample {
   public static void main(String[] args) throws Exception {

      //Creating the CredentialsProvider object
      CredentialsProvider credsProvider = new BasicCredentialsProvider();

      //Setting the credentials
      credsProvider.setCredentials(new AuthScope("example.com", 80), 
         new UsernamePasswordCredentials("user", "mypass"));
      credsProvider.setCredentials(new AuthScope("localhost", 8000), 
         new UsernamePasswordCredentials("abc", "passwd"));

      //Creating the HttpClientBuilder
      HttpClientBuilder clientbuilder = HttpClients.custom();

      //Setting the credentials
      clientbuilder = clientbuilder.setDefaultCredentialsProvider(credsProvider);
      
      //Building the CloseableHttpClient object
      CloseableHttpClient httpclient = clientbuilder.build();


      //Create the target and proxy hosts
      HttpHost targetHost = new HttpHost("example.com", 80, "http");
      HttpHost proxyHost = new HttpHost("localhost", 8000, "http");

      //Setting the proxy
      RequestConfig.Builder reqconfigconbuilder= RequestConfig.custom();
      reqconfigconbuilder = reqconfigconbuilder.setProxy(proxyHost);
      RequestConfig config = reqconfigconbuilder.build();

      //Create the HttpGet request object
      HttpGet httpget = new HttpGet("/");

      //Setting the config to the request
      httpget.setConfig(config);
 
      //Printing the status line
      HttpResponse response = httpclient.execute(targetHost, httpget);
      System.out.println(response.getStatusLine());

   }
}

输出

执行上述程序后，将生成以下输出：

HTTP/1.1 200 OK

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