httclient使用socket發送請求

 socket        

Socket的英文原義是“孔”或“插座”。作爲BSD UNIX的進程機制，取後一種意思。通常也稱作"套接字"，用於描述IP地址和端口，是一個通信鏈的句柄，可以用來實現不同虛擬機或不同計算機之間的通信。在Internet上的主機一般運行了多個服務軟件，同時提供幾種服務。每種服務都打開一個Socket，並綁定到一個端口上，不同的端口對應於不同的服務。Socket正如其英文原意那樣，像一個多孔插座。一臺主機猶如佈滿各種插座的房間，每個插座有一個編號，有的插座提供220伏交流電， 有的提供110伏交流電，有的則提供有線電視節目。 客戶軟件將插頭插到不同編號的插座，就可以得到不同的服務。

先看一個使用httpclient發送請求的例子

package com.j.test;


import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpClient;
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.util.EntityUtils;


import java.io.IOException;


/**
 * Created by brady on 16-1-30.
 */
public class HttpClientImpl {
    public static void main(String[] args) {
        //創建HttpClientBuilder
        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
        //HttpClient
        CloseableHttpClient closeableHttpClient = httpClientBuilder.build();


        HttpGet httpGet = new HttpGet("http://www.baidu.com");
        System.out.println(httpGet.getRequestLine());
        try {
            //執行get請求
            HttpResponse httpResponse = closeableHttpClient.execute(httpGet);
            //獲取響應消息實體
            HttpEntity entity = httpResponse.getEntity();
            //響應狀態
            System.out.println("status:" + httpResponse.getStatusLine());
            //判斷響應實體是否爲空
            if (entity != null) {
                System.out.println("contentEncoding:" + entity.getContentEncoding());
                System.out.println("response content:" + EntityUtils.toString(entity));
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                //關閉流並釋放資源
                closeableHttpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

順着代碼可以看到PoolingHttpClientConnectionManager的routeComplete方法

    public void connect(
            final HttpClientConnection managedConn,
            final HttpRoute route,
            final int connectTimeout,
            final HttpContext context) throws IOException {
        Args.notNull(managedConn, "Managed Connection");
        Args.notNull(route, "HTTP route");
        final ManagedHttpClientConnection conn;
        synchronized (managedConn) {
            final CPoolEntry entry = CPoolProxy.getPoolEntry(managedConn);
            conn = entry.getConnection();
        }
        final HttpHost host;
        if (route.getProxyHost() != null) {
            host = route.getProxyHost();
        } else {
            host = route.getTargetHost();
        }
        final InetSocketAddress localAddress = route.getLocalSocketAddress();
        SocketConfig socketConfig = this.configData.getSocketConfig(host);
        if (socketConfig == null) {
            socketConfig = this.configData.getDefaultSocketConfig();
        }
        if (socketConfig == null) {
            socketConfig = SocketConfig.DEFAULT;
        }
        this.connectionOperator.connect(
                conn, host, localAddress, connectTimeout, socketConfig, context);
    }

然後調用到HttpClientConnectionOperator的connect方法

    public void connect(
            final ManagedHttpClientConnection conn,
            final HttpHost host,
            final InetSocketAddress localAddress,
            final int connectTimeout,
            final SocketConfig socketConfig,
            final HttpContext context) throws IOException {
        final Lookup<ConnectionSocketFactory> registry = getSocketFactoryRegistry(context);
        final ConnectionSocketFactory sf = registry.lookup(host.getSchemeName());
        if (sf == null) {
            throw new UnsupportedSchemeException(host.getSchemeName() +
                    " protocol is not supported");
        }
        final InetAddress[] addresses = this.dnsResolver.resolve(host.getHostName());
        final int port = this.schemePortResolver.resolve(host);
        for (int i = 0; i < addresses.length; i++) {
            final InetAddress address = addresses[i];
            final boolean last = i == addresses.length - 1;

            Socket sock = sf.createSocket(context);
            sock.setSoTimeout(socketConfig.getSoTimeout());
            sock.setReuseAddress(socketConfig.isSoReuseAddress());
            sock.setTcpNoDelay(socketConfig.isTcpNoDelay());
            sock.setKeepAlive(socketConfig.isSoKeepAlive());
            final int linger = socketConfig.getSoLinger();
            if (linger >= 0) {
                sock.setSoLinger(linger > 0, linger);
            }
            conn.bind(sock);

            final InetSocketAddress remoteAddress = new InetSocketAddress(address, port);
            if (this.log.isDebugEnabled()) {
                this.log.debug("Connecting to " + remoteAddress);
            }
            try {
                sock = sf.connectSocket(
                        connectTimeout, sock, host, remoteAddress, localAddress, context);
                conn.bind(sock);
                if (this.log.isDebugEnabled()) {
                    this.log.debug("Connection established " + conn);
                }
                return;
            } catch (final SocketTimeoutException ex) {
                if (last) {
                    throw new ConnectTimeoutException(ex, host, addresses);
                }
            } catch (final ConnectException ex) {
                if (last) {
                    final String msg = ex.getMessage();
                    if ("Connection timed out".equals(msg)) {
                        throw new ConnectTimeoutException(ex, host, addresses);
                    } else {
                        throw new HttpHostConnectException(ex, host, addresses);
                    }
                }
            }
            if (this.log.isDebugEnabled()) {
                this.log.debug("Connect to " + remoteAddress + " timed out. " +
                        "Connection will be retried using another IP address");
            }
        }
    }