Http请求连接池 - HttpClient 的 PoolingHttpClientConnectionManager

两个主机建立连接的过程是非常复杂的一个过程，涉及到多个数据包的交换，而且也非常耗时间。Http连接须要的三次握手开销非常大，这一开销对于比較小的http消息来说更大。但是假设我们直接使用已经建立好的http连接。这样花费就比較小。吞吐率更大。
传统的HttpURLConnection并不支持连接池。假设要实现连接池的机制，还须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。个人以为假设有可用的其它方案，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。普通情况下，普通使用HttpClient已经能满足我们的需求，只是有时候。在我们须要高并发大量的请求网络的时候，还是用“连接池”这种概念能提升吞吐量。

我们来看下怎么使用 org.apache.httpcomponents.httpclient（版本号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

以下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<ConnectionSocketFactory> registry = RegistryBuilder
                .<ConnectionSocketFactory> create().register("http", plainsf)
                .register("https", sslsf).build();
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(
                registry);
        // 将最大连接数添加
        cm.setMaxTotal(maxTotal);
        // 将每一个路由基础的连接添加
        cm.setDefaultMaxPerRoute(maxPerRoute);
        HttpHost httpHost = new HttpHost(hostname, port);
        // 将目标主机的最大连接数添加
        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) {// 假设已经重试了5次，就放弃
                    return false;
                }
                if (exception instanceof NoHttpResponseException) {// 假设server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server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();
                // 假设请求是幂等的，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<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) {
//          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() + ", 全部线程已完毕。開始进入下一步！
");
        }

        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();
            }
        }
    }
}

Post用法

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

一開始我是使用传统的 HttpURLConnection 来做网络请求的。查了非常多资料，有不少说 HttpURLConnection 效率高的。但是经过我改动实现方法后，HttpClient 连接池版本号的网络请求相对照较稳定。

这也说明，我们并不请尽信他人讲解，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。以下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);// 对參数进行加密签名
        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）