Apache HttpClient - 多线程
多线程程序包含两个或多个可以并发运行的部分，每个部分可以同时处理不同的任务，从而最大程度地利用可用资源。
您可以通过编写多线程 HttpClient 程序来从多个线程执行请求。
如果您想从线程连续执行多个客户端请求，则需要创建一个**ClientConnectionPoolManager**。它维护一个**HttpClientConnections**池，并为来自线程的多个请求提供服务。
连接管理器根据路由对连接进行池化。如果管理器具有特定路由的连接，则它通过从池中租用现有连接来为这些路由中的新请求提供服务，而不是创建新的连接。
请按照以下步骤从多个线程执行请求：
步骤 1 - 创建客户端连接池管理器
通过实例化**PoolingHttpClientConnectionManager**类来创建客户端连接池管理器。
PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();
步骤 2 - 设置最大连接数
使用**setMaxTotal()**方法设置池中的最大连接数。
//Set the maximum number of connections in the pool connManager.setMaxTotal(100);
步骤 3 - 创建 ClientBuilder 对象
通过使用**setConnectionManager()**方法设置连接管理器来创建一个**ClientBuilder**对象，如下所示：
HttpClientBuilder clientbuilder = HttpClients.custom().setConnectionManager(connManager);
步骤 4 - 创建 HttpGet 请求对象
通过将所需的 URI 作为参数传递给其构造函数来实例化 HttpGet 类。
HttpGet httpget1 = new HttpGet("URI1");
HttpGet httpget2 = new HttpGet("URI2");
. . . . . . . . . . . .
步骤 5 - 实现 run 方法
确保您已创建一个类，并将其设为线程（通过扩展线程类或实现 Runnable 接口），并实现了 run 方法。
public class ClientMultiThreaded extends Thread {
public void run() {
//Run method implementation . . . . . . . . . .
}
}
步骤 6 - 创建线程对象
通过实例化上面创建的 Thread 类（ClientMultiThreaded）来创建线程对象。
将 HttpClient 对象、相应的 HttpGet 对象和表示 ID 的整数传递给这些线程。
ClientMultiThreaded thread1 = new ClientMultiThreaded(httpclient,httpget1, 1); ClientMultiThreaded thread2 = new ClientMultiThreaded(httpclient,httpget2, 2); . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
步骤 7 - 启动并连接线程
使用**start()**方法启动所有线程，并使用 join **method()**方法连接它们。
thread1.start(); thread2.start(); . . . . . . . . thread1.join(); thread2.join(); . . . . . . . . . . . .
步骤 8 - Run 方法实现
在 run 方法中，执行请求，检索响应并打印结果。
示例
以下示例演示了从多个线程同时执行 HTTP 请求。在此示例中，我们尝试从各个线程执行各种请求，并尝试打印每个客户端的状态和读取的字节数。
import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.util.EntityUtils;
public class ClientMultiThreaded extends Thread {
CloseableHttpClient httpClient;
HttpGet httpget;
int id;
public ClientMultiThreaded(CloseableHttpClient httpClient, HttpGet httpget,
int id) {
this.httpClient = httpClient;
this.httpget = httpget;
this.id = id;
}
@Override
public void run() {
try{
//Executing the request
CloseableHttpResponse httpresponse = httpClient.execute(httpget);
//Displaying the status of the request.
System.out.println("status of thread "+id+":"+httpresponse.getStatusLine());
//Retrieving the HttpEntity and displaying the no.of bytes read
HttpEntity entity = httpresponse.getEntity();
if (entity != null) {
System.out.println("Bytes read by thread thread "+id+":
"+EntityUtils.toByteArray(entity).length);
}
}catch(Exception e) {
System.out.println(e.getMessage());
}
}
public static void main(String[] args) throws Exception {
//Creating the Client Connection Pool Manager by instantiating the PoolingHttpClientConnectionManager class.
PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();
//Set the maximum number of connections in the pool
connManager.setMaxTotal(100);
//Create a ClientBuilder Object by setting the connection manager
HttpClientBuilder clientbuilder = HttpClients.custom().setConnectionManager(connManager);
//Build the CloseableHttpClient object using the build() method.
CloseableHttpClient httpclient = clientbuilder.build();
//Creating the HttpGet requests
HttpGet httpget1 = new HttpGet("https://tutorialspoint.com/");
HttpGet httpget2 = new HttpGet("http://www.google.com/");
HttpGet httpget3 = new HttpGet("https://www.qries.com/");
HttpGet httpget4 = new HttpGet("https://in.yahoo.com/");
//Creating the Thread objects
ClientMultiThreaded thread1 = new ClientMultiThreaded(httpclient,httpget1, 1);
ClientMultiThreaded thread2 = new ClientMultiThreaded(httpclient,httpget2, 2);
ClientMultiThreaded thread3 = new ClientMultiThreaded(httpclient,httpget3, 3);
ClientMultiThreaded thread4 = new ClientMultiThreaded(httpclient,httpget4, 4);
//Starting all the threads
thread1.start();
thread2.start();
thread3.start();
thread4.start();
//Joining all the threads
thread1.join();
thread2.join();
thread3.join();
thread4.join();
}
}
输出
执行上述程序后，将生成以下输出：
status of thread 1: HTTP/1.1 200 OK Bytes read by thread thread 1: 36907 status of thread 2: HTTP/1.1 200 OK Bytes read by thread thread 2: 13725 status of thread 3: HTTP/1.1 200 OK Bytes read by thread thread 3: 17319 status of thread 4: HTTP/1.1 200 OK Bytes read by thread thread 4: 127018
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