Http请求连接池 - HttpClient 的 PoolingHttpClientConnectionManager

两个主机建立连接的过程是很复杂的一个过程，涉及到多个数据包的交换，并且也很耗时间。Http连接需要的三次握手开销很大，这一开销对于比较小的http消息来说更大。但是如果我们直接使用已经建立好的http连接，这样花费就比较小，吞吐率更大。
传统的HttpURLConnection并不支持连接池，如果要实现连接池的机制，还需要自己来管理连接对象。对于网络请求这种底层相对复杂的操作，个人以为如果有可用的其他方案，也没有必要自己去管理连接对象。

除了HttpURLConnection，大家肯定还知道HttpClient。一般情况下，普通使用HttpClient已经能满足我们的需求，不过有时候，在我们需要高并发大量的请求网络的时候，还是用“连接池”这样的概念能提升吞吐量。

我们来看下怎么使用 org.apache.httpcomponents.httpclient（版本4.4）提供的连接池来实现我们的高并发网络请求。

使用到的jar包：
org\apache\httpcomponents\httpclient\4.4-beta1\httpclient-4.4-beta1.jar
org\apache\httpcomponents\httpclient-cache\4.4-beta1\httpclient-cache-4.4-beta1.jar
org\apache\httpcomponents\httpcore\4.4-beta1\httpcore-4.4-beta1.jar

下面代码实例中主要使用到 PoolingHttpClientConnectionManager

package com.hvgroup.zhuhai10086.jms.utils;import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.UnsupportedEncodingException;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;import javax.net.ssl.SSLException;
import javax.net.ssl.SSLHandshakeException;import org.apache.http.HttpEntity;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.NameValuePair;
import org.apache.http.NoHttpResponseException;
import org.apache.http.client.HttpRequestRetryHandler;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.ConnectTimeoutException;
import org.apache.http.conn.routing.HttpRoute;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.LayeredConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
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.message.BasicNameValuePair;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;/*** HttpClient工具类* * @return* @author SHANHY* @create 2015年12月18日*/
public class HttpClientUtil {static final int timeOut = 10 * 1000;private static CloseableHttpClient httpClient = null;private final static Object syncLock = new Object();private static void config(HttpRequestBase httpRequestBase) {// 设置Header等// httpRequestBase.setHeader("User-Agent", "Mozilla/5.0");// httpRequestBase// .setHeader("Accept",// "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");// httpRequestBase.setHeader("Accept-Language",// "zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3");// "en-US,en;q=0.5");// httpRequestBase.setHeader("Accept-Charset",// "ISO-8859-1,utf-8,gbk,gb2312;q=0.7,*;q=0.7");// 配置请求的超时设置RequestConfig requestConfig = RequestConfig.custom().setConnectionRequestTimeout(timeOut).setConnectTimeout(timeOut).setSocketTimeout(timeOut).build();httpRequestBase.setConfig(requestConfig);}/*** 获取HttpClient对象* * @return* @author SHANHY* @create 2015年12月18日*/public static CloseableHttpClient getHttpClient(String url) {String hostname = url.split("/")[2];int port = 80;if (hostname.contains(":")) {String[] arr = hostname.split(":");hostname = arr[0];port = Integer.parseInt(arr[1]);}if (httpClient == null) {synchronized (syncLock) {if (httpClient == null) {httpClient = createHttpClient(200, 40, 100, hostname, port);}}}return httpClient;}/*** 创建HttpClient对象* * @return* @author SHANHY* @create 2015年12月18日*/public static CloseableHttpClient createHttpClient(int maxTotal,int maxPerRoute, int maxRoute, String hostname, int port) {ConnectionSocketFactory plainsf = PlainConnectionSocketFactory.getSocketFactory();LayeredConnectionSocketFactory sslsf = SSLConnectionSocketFactory.getSocketFactory();Registry registry = RegistryBuilder. create().register("http", plainsf).register("https", sslsf).build();PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(registry);// 将最大连接数增加cm.setMaxTotal(maxTotal);// 将每个路由基础的连接增加cm.setDefaultMaxPerRoute(maxPerRoute);HttpHost httpHost = new HttpHost(hostname, port);// 将目标主机的最大连接数增加cm.setMaxPerRoute(new HttpRoute(httpHost), maxRoute);// 请求重试处理HttpRequestRetryHandler httpRequestRetryHandler = new HttpRequestRetryHandler() {public boolean retryRequest(IOException exception,int executionCount, HttpContext context) {if (executionCount >= 5) {// 如果已经重试了5次，就放弃return false;}if (exception instanceof NoHttpResponseException) {// 如果服务器丢掉了连接，那么就重试return true;}if (exception instanceof SSLHandshakeException) {// 不要重试SSL握手异常return false;}if (exception instanceof InterruptedIOException) {// 超时return false;}if (exception instanceof UnknownHostException) {// 目标服务器不可达return false;}if (exception instanceof ConnectTimeoutException) {// 连接被拒绝return false;}if (exception instanceof SSLException) {// SSL握手异常return false;}HttpClientContext clientContext = HttpClientContext.adapt(context);HttpRequest request = clientContext.getRequest();// 如果请求是幂等的，就再次尝试if (!(request instanceof HttpEntityEnclosingRequest)) {return true;}return false;}};CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(cm).setRetryHandler(httpRequestRetryHandler).build();return httpClient;}private static void setPostParams(HttpPost httpost,Map params) {List nvps = new ArrayList();Set keySet = params.keySet();for (String key : keySet) {nvps.add(new BasicNameValuePair(key, params.get(key).toString()));}try {httpost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}}/*** GET请求URL获取内容* * @param url* @return* @author SHANHY* @throws IOException * @create 2015年12月18日*/public static String post(String url, Map params) throws IOException {HttpPost httppost = new HttpPost(url);config(httppost);setPostParams(httppost, params);CloseableHttpResponse response = null;try {response = getHttpClient(url).execute(httppost,HttpClientContext.create());HttpEntity entity = response.getEntity();String result = EntityUtils.toString(entity, "utf-8");EntityUtils.consume(entity);return result;} catch (Exception e) {
//          e.printStackTrace();throw e;} finally {try {if (response != null)response.close();} catch (IOException e) {e.printStackTrace();}}}/*** GET请求URL获取内容* * @param url* @return* @author SHANHY* @create 2015年12月18日*/public static String get(String url) {HttpGet httpget = new HttpGet(url);config(httpget);CloseableHttpResponse response = null;try {response = getHttpClient(url).execute(httpget,HttpClientContext.create());HttpEntity entity = response.getEntity();String result = EntityUtils.toString(entity, "utf-8");EntityUtils.consume(entity);return result;} catch (IOException e) {e.printStackTrace();} finally {try {if (response != null)response.close();} catch (IOException e) {e.printStackTrace();}}return null;}public static void main(String[] args) {// URL列表数组String[] urisToGet = {"http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497","http://blog.csdn.net/catoop/article/details/38849497" };long start = System.currentTimeMillis();try {int pagecount = urisToGet.length;ExecutorService executors = Executors.newFixedThreadPool(pagecount);CountDownLatch countDownLatch = new CountDownLatch(pagecount);for (int i = 0; i < pagecount; i++) {HttpGet httpget = new HttpGet(urisToGet[i]);config(httpget);// 启动线程抓取executors.execute(new GetRunnable(urisToGet[i], countDownLatch));}countDownLatch.await();executors.shutdown();} catch (InterruptedException e) {e.printStackTrace();} finally {System.out.println("线程" + Thread.currentThread().getName() + ","+ System.currentTimeMillis() + ", 所有线程已完成，开始进入下一步！");}long end = System.currentTimeMillis();System.out.println("consume -> " + (end - start));}static class GetRunnable implements Runnable {private CountDownLatch countDownLatch;private String url;public GetRunnable(String url, CountDownLatch countDownLatch) {this.url = url;this.countDownLatch = countDownLatch;}@Overridepublic void run() {try {System.out.println(HttpClientUtil.get(url));} finally {countDownLatch.countDown();}}}
}

Post使用方法

// 其中 params 为 Map<String, Object> params
String ret = HttpClientUtil.post(url, params);jsonRet = new JSONObject(ret);

一开始我是使用传统的 HttpURLConnection 来做网络请求的，查了很多资料，有不少说 HttpURLConnection 效率高的。可是经过我修改实现方法后，HttpClient 连接池版本的网络请求相对比较稳定。这也说明，我们并不请尽信他人解说，凡事还是要寻找适合自己的方法，真正的解决自己的问题，才是王道。

===========================================

在使用 HttpURLConnection 的时候，大并发对外做网络请求的时候，前期请求耗时还好，后面耗时越来越高。下面是我之前的实现代码：

    @Deprecatedprotected JSONObject callRestfulOld(String url, Map params) {String temp;String ret="";JSONObject jsonRet=null;String sign = generateSign("POST", url, params);// 对参数进行加密签名if(sign.isEmpty()) return new JSONObject("{\"ret_code\":-1,\"err_msg\":\"generateSign error\"}");params.put("sign", sign);try{URL u = new URL(url);HttpURLConnection conn = (HttpURLConnection)u.openConnection();conn.setRequestMethod("POST");conn.setConnectTimeout(10000);conn.setDoOutput(true);conn.setDoInput(true);conn.setUseCaches(false);StringBuffer param = new StringBuffer();for (String key: params.keySet()){param.append(key).append("=").append(URLEncoder.encode(params.get(key).toString(), "UTF-8")).append("&");}conn.getOutputStream().write(param.toString().getBytes("UTF-8"));//System.out.println(param);conn.getOutputStream().flush();conn.getOutputStream().close();InputStreamReader isr = new InputStreamReader(conn.getInputStream());  BufferedReader br = new BufferedReader(isr);  while((temp = br.readLine()) != null){  ret += temp;  }     br.close();  isr.close();conn.disconnect();//System.out.println(ret);jsonRet = new JSONObject(ret);} catch(java.net.SocketTimeoutException e) {//e.printStackTrace();jsonRet = new JSONObject("{\"ret_code\":-1,\"err_msg\":\"call restful timeout\"}");} catch(Exception e) {//e.printStackTrace();jsonRet = new JSONObject("{\"ret_code\":-1,\"err_msg\":\"call restful error\"}");}return jsonRet;}

（完）

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