Java reptile entry to the master (four) - Connection Pooling

The use of connection pooling HttpClient frequent way to solve the problem of creation and destruction

A complete project reptile can never be executed only once request, so there will be a question frequently HttpClient creation and destruction, this problem can be solved using a connection pool.

Creating HttpClientPoolTest.java, you can create a breakpoint in HttpGet to see if the same HttpClient.

package crawler.test;

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.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientPoolTest {

    public static void main(String[] args) {

//        创建连接池管理器
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();

//        设置最大连接数
        cm.setMaxTotal(100);

//        设置每台主机的最大连接数
        cm.setDefaultMaxPerRoute(10);

        //使用连接池管理器发起请求
        doGet(cm);
        doGet(cm);
    }

    private static void doGet(PoolingHttpClientConnectionManager cm) {

        //不是每次创建新的HttpClient，而是从连接池中获取HttpClient对象
        CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(cm).build();

        HttpGet httpGet = new HttpGet("https://baidu.com");

        CloseableHttpResponse response = null;

        try {
            response = httpClient.execute(httpGet);

            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "utf8");
                System.out.println(content.length());
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
//                不能关闭HttpClient,由连接池管理的
//                httpClient.close();
            }
        }

    }

}

Create a breakpoint, run with debug

HttpCilent can see two objects Value is not the same