http://blog.csdn.net/catoop/article/details/50352334
只有一个httpclient的实例，你可以看看CloseableHttpClient和PoolingHttpClientConnectionManager的源码,你会发现httpclient实例通过execute执行get或post获取连接的时候，会通过实例关联的connectionManager的connect()来建立连接，这里的connectionManager是一个连接池的实现, 因此connect方法调用的是PoolingHttpClientConnectionManager重写的实现，这就是一个连接池建立连接的实现，具体还是看源码吧
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) { 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<ConnectionSocketFactory> registry = RegistryBuilder .<ConnectionSocketFactory> create().register("http", plainsf) .register("https", sslsf).build(); PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager( registry); cm.setMaxTotal(maxTotal); cm.setDefaultMaxPerRoute(maxPerRoute); HttpHost httpHost = new HttpHost(hostname, port); cm.setMaxPerRoute(new HttpRoute(httpHost), maxRoute); HttpRequestRetryHandler httpRequestRetryHandler = new HttpRequestRetryHandler() { public boolean retryRequest(IOException exception, int executionCount, HttpContext context) { if (executionCount >= 5) { return false; } if (exception instanceof NoHttpResponseException) { return true; } if (exception instanceof SSLHandshakeException) { return false; } if (exception instanceof InterruptedIOException) { return false; } if (exception instanceof UnknownHostException) { return false; } if (exception instanceof ConnectTimeoutException) { return false; } if (exception instanceof SSLException) { return false; } HttpClientContext clientContext = HttpClientContext .adapt(context); HttpRequest request = clientContext.getRequest(); 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<String, Object> params) { List<NameValuePair> nvps = new ArrayList<NameValuePair>(); Set<String> 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<String, Object> 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) { 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) { 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); 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; } @Override public void run() { try { System.out.println(HttpClientUtil.get(url)); } finally { countDownLatch.countDown(); } } }}
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Post使用方法
// 其中 params 为 Map<String, Object> paramsString 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。
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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：
@Deprecated protected JSONObject callRestfulOld(String url, Map<String, Object> params) { String temp String ret="" JSONObject jsonRet=null String sign = generateSign("POST", url, params) 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 }
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（完）
