apache httpclient连接池PoolingHttpClientConnectionManager

一、首先,明确以下内容:

1.http连接池不是万能的,过多的长连接会占用服务器资源,导致其他服务受阻
2.http连接池只适用于请求是经常访问同一主机(或同一个接口)的情况下
3.并发数不高的情况下资源利用率低下

那么,当你的业务符合上面3点,那么你可以考虑使用http连接池来提高服务器性能

使用http连接池的优点:

1.复用http连接,省去了tcp的3次握手和4次挥手的时间,极大降低请求响应的时间
2.自动管理tcp连接,不用人为地释放/创建连接

使用http连接池的大致流程 :

1.创建PoolingHttpClientConnectionManager实例
2.给manager设置参数
3.给manager设置重试策略
4.给manager设置连接管理策略
5.开启监控线程,及时关闭被服务器单向断开的连接
6.构建HttpClient实例
7.创建HttpPost/HttpGet实例,并设置参数
8.获取响应,做适当的处理
9.将用完的连接放回连接池

二、实践

1、网上文章

网址：https://www.jianshu.com/p/c852cbcf3d68

public class HttpConnectionPoolUtil {

    private static Logger logger = LoggerFactory.getLogger(HttpConnectionPoolUtil.class);

    private static final int CONNECT_TIMEOUT = Config.getHttpConnectTimeout();// 设置连接建立的超时时间为10s
    private static final int SOCKET_TIMEOUT = Config.getHttpSocketTimeout();
    private static final int MAX_CONN = Config.getHttpMaxPoolSize(); // 最大连接数
    private static final int Max_PRE_ROUTE = Config.getHttpMaxPoolSize();
    private static final int MAX_ROUTE = Config.getHttpMaxPoolSize();
    private static CloseableHttpClient httpClient; // 发送请求的客户端单例
    private static PoolingHttpClientConnectionManager manager; //连接池管理类
    private static ScheduledExecutorService monitorExecutor;

    private final static Object syncLock = new Object(); // 相当于线程锁,用于线程安全

    /**
     * 对http请求进行基本设置
     * @param httpRequestBase http请求
     */
    private static void setRequestConfig(HttpRequestBase httpRequestBase){
        RequestConfig requestConfig = RequestConfig.custom().setConnectionRequestTimeout(CONNECT_TIMEOUT)
                .setConnectTimeout(CONNECT_TIMEOUT)
                .setSocketTimeout(SOCKET_TIMEOUT).build();

        httpRequestBase.setConfig(requestConfig);
    }

    public static CloseableHttpClient getHttpClient(String url){
        String hostName = url.split("/")[2];
        System.out.println(hostName);
        int port = 80;
        if (hostName.contains(":")){
            String[] args = hostName.split(":");
            hostName = args[0];
            port = Integer.parseInt(args[1]);
        }

        if (httpClient == null){
            //多线程下多个线程同时调用getHttpClient容易导致重复创建httpClient对象的问题,所以加上了同步锁
            synchronized (syncLock){
                if (httpClient == null){
                    httpClient = createHttpClient(hostName, port);
                    //开启监控线程,对异常和空闲线程进行关闭
                    monitorExecutor = Executors.newScheduledThreadPool(1);
                    monitorExecutor.scheduleAtFixedRate(new TimerTask() {
                        @Override
                        public void run() {
                            //关闭异常连接
                            manager.closeExpiredConnections();
                            //关闭5s空闲的连接
                            manager.closeIdleConnections(Config.getHttpIdelTimeout(), TimeUnit.MILLISECONDS);
                            logger.info("close expired and idle for over 5s connection");
                        }
                    }, Config.getHttpMonitorInterval(), Config.getHttpMonitorInterval(), TimeUnit.MILLISECONDS);
                }
            }
        }
        return httpClient;
    }

    /**
     * 根据host和port构建httpclient实例
     * @param host 要访问的域名
     * @param port 要访问的端口
     * @return
     */
    public static CloseableHttpClient createHttpClient(String host, int port){
        ConnectionSocketFactory plainSocketFactory = PlainConnectionSocketFactory.getSocketFactory();
        LayeredConnectionSocketFactory sslSocketFactory = SSLConnectionSocketFactory.getSocketFactory();
        Registry registry = RegistryBuilder. create().register("http", plainSocketFactory)
                .register("https", sslSocketFactory).build();

        manager = new PoolingHttpClientConnectionManager(registry);
        //设置连接参数
        manager.setMaxTotal(MAX_CONN); // 最大连接数
        manager.setDefaultMaxPerRoute(Max_PRE_ROUTE); // 路由最大连接数

        HttpHost httpHost = new HttpHost(host, port);
        manager.setMaxPerRoute(new HttpRoute(httpHost), MAX_ROUTE);

        //请求失败时,进行请求重试
        HttpRequestRetryHandler handler = new HttpRequestRetryHandler() {
            @Override
            public boolean retryRequest(IOException e, int i, HttpContext httpContext) {
                if (i > 3){
                    //重试超过3次,放弃请求
                    logger.error("retry has more than 3 time, give up request");
                    return false;
                }
                if (e instanceof NoHttpResponseException){
                    //服务器没有响应,可能是服务器断开了连接,应该重试
                    logger.error("receive no response from server, retry");
                    return true;
                }
                if (e instanceof SSLHandshakeException){
                    // SSL握手异常
                    logger.error("SSL hand shake exception");
                    return false;
                }
                if (e instanceof InterruptedIOException){
                    //超时
                    logger.error("InterruptedIOException");
                    return false;
                }
                if (e instanceof UnknownHostException){
                    // 服务器不可达
                    logger.error("server host unknown");
                    return false;
                }
                if (e instanceof ConnectTimeoutException){
                    // 连接超时
                    logger.error("Connection Time out");
                    return false;
                }
                if (e instanceof SSLException){
                    logger.error("SSLException");
                    return false;
                }

                HttpClientContext context = HttpClientContext.adapt(httpContext);
                HttpRequest request = context.getRequest();
                if (!(request instanceof HttpEntityEnclosingRequest)){
                    //如果请求不是关闭连接的请求
                    return true;
                }
                return false;
            }
        };

        CloseableHttpClient client = HttpClients.custom().setConnectionManager(manager).setRetryHandler(handler).build();
        return client;
    }

    /**
     * 设置post请求的参数
     * @param httpPost
     * @param params
     */
    private static void setPostParams(HttpPost httpPost, Map params){
        List nvps = new ArrayList();
        Set keys = params.keySet();
        for (String key: keys){
            nvps.add(new BasicNameValuePair(key, params.get(key)));
        }
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(nvps, "utf-8"));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
    }

    public static JsonObject post(String url, Map params){
        HttpPost httpPost = new HttpPost(url);
        setRequestConfig(httpPost);
        setPostParams(httpPost, params);
        CloseableHttpResponse response = null;
        InputStream in = null;
        JsonObject object = null;
        try {
            response = getHttpClient(url).execute(httpPost, HttpClientContext.create());
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                in = entity.getContent();
                String result = IOUtils.toString(in, "utf-8");
                Gson gson = new Gson();
                object = gson.fromJson(result, JsonObject.class);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try{
                if (in != null) in.close();
                if (response != null) response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return object;
    }

    /**
     * 关闭连接池
     */
    public static void closeConnectionPool(){
        try {
            httpClient.close();
            manager.close();
            monitorExecutor.shutdown();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2、网上文章

网址：https://www.wandouip.com/t5i72494/

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;
 

public class HttpClientUtil {
 
    static final int timeOut = 1000;
    private CloseableHttpClient httpClient = null;
    private IdleConnectionMonitorThread idleConnectionMonitor = 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);
    }
 
    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(1024, 32, 64, hostname, port);
                }
            }
        }
        return httpClient;
    }
 
    public static CloseableHttpClient createHttpClient(int maxTotal,int maxPerRoute, int maxRoute, String hostname, int port) {
        
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
        // 设置最大连接数
        cm.setMaxTotal(maxTotal);
        // 将每个路由默认最大连接数
        cm.setDefaultMaxPerRoute(maxPerRoute);
        HttpHost httpHost = new HttpHost(hostname, port);
        // 设置目标主机对应的路由的最大连接数，会覆盖setDefaultMaxPerRoute设置的默认值
        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 >= 3) {// 如果已经重试了3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();
        idleConnectionMonitor = new IdleConnectionMonitorThread(cm);
        idleConnectionMonitor.start();
 
        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();
        }
    }
 
    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();
            }
        }
    }
 
    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);   //关闭HttpEntity是的流，如果手动关闭了InputStream instream = entity.getContent();这个流，也可以不调用这个方法
            return result;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null)
                    response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }
    
    //用于监控空闲的连接池连接
    private final class IdleConnectionMonitorThread extends Thread {
        private final HttpClientConnectionManager connMgr;
        private volatile boolean shutdown;

        private static final int MONITOR_INTERVAL_MS = 2000;
        private static final int IDLE_ALIVE_MS = 5000;

        public IdleConnectionMonitorThread(HttpClientConnectionManager connMgr) {
             super();
             this.connMgr = connMgr;
             this.shutdown = false;
        }

        @Override
        public void run() {
            try {
                while (!shutdown) {
                    synchronized (this) {
                        wait(MONITOR_INTERVAL_MS);
                        // 关闭无效的连接
                        connMgr.closeExpiredConnections();
                        // 关闭空闲时间超过IDLE_ALIVE_MS的连接
                        connMgr.closeIdleConnections(IDLE_ALIVE_MS, TimeUnit.MILLISECONDS);
                }
            }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        // 关闭后台连接
        public void shutdown() {
            shutdown = true;
            synchronized (this) {
                notifyAll();
            }
        }
    }
 
}

3、网上文章

代码网址：

https://blog.csdn.net/ll641058431/article/details/79566277

4、网上文章

采用连接池进行优化后，如果还需要进一步优化：移步下面文章

https://blog.csdn.net/superiorpengFight/article/details/104007627?utm_medium=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param

上面文章除了池化技术优化外，还包括：反复创建tcp连接的开销、重复缓存entity的开销两项优化方案

三、关键的地方有以下几点

• httpclient实例必须是单例,且该实例必须使用HttpClients.custom().setConnectionManager()来绑定一个PollingHttpClientConnectionManager,这样该client每次发送请求都会通过manager来获取连接,如果连接池中没有可用连接的话,则该会阻塞线程,直到有可用的连接
• httpclients4.5.x版本直接调用ClosableHttpResponse.close()就能直接把连接放回连接池,而不是关闭连接,以前的版本貌似要调用其他方法才能把连接放回连接池
• 由于服务器一般不会允许无限期的长连接,所以需要开启监控线程,每隔一段时间就检测一下连接池中连接的情况,及时关闭异常连接和长时间空闲的连接,避免占用服务器资源.