httclient使用socket发送请求

 socket 
      

Socket的英文原义是“孔”或“插座”。作为BSD UNIX的进程机制，取后一种意思。通常也称作"套接字"，用于描述IP地址和端口，是一个通信链的句柄，可以用来实现不同虚拟机或不同计算机之间的通信。在Internet上的主机一般运行了多个服务软件，同时提供几种服务。每种服务都打开一个Socket，并绑定到一个端口上，不同的端口对应于不同的服务。Socket正如其英文原意那样，像一个多孔插座。一台主机犹如布满各种插座的房间，每个插座有一个编号，有的插座提供220伏交流电，
有的提供110伏交流电，有的则提供有线电视节目。 客户软件将插头插到不同编号的插座，就可以得到不同的服务。

先看一个使用httpclient发送请求的例子

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) {
//创建HttpClientBuilder
HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
//HttpClient
CloseableHttpClient closeableHttpClient = httpClientBuilder.build();

HttpGet httpGet = new HttpGet("http://www.baidu.com");
System.out.println(httpGet.getRequestLine());
try {
//执行get请求
HttpResponse httpResponse = closeableHttpClient.execute(httpGet);
//获取响应消息实体
HttpEntity entity = httpResponse.getEntity();
//响应状态
System.out.println("status:" + httpResponse.getStatusLine());
//判断响应实体是否为空
if (entity != null) {
System.out.println("contentEncoding:" + entity.getContentEncoding());
System.out.println("response content:" + EntityUtils.toString(entity));
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
//关闭流并释放资源
closeableHttpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

顺着代码可以看到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);
}


然后调用到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
4000
) {
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");
}
}
}