http连接池

看到了一篇文章，是关于发送http请求时，响应时间过长的问题的解决。

侵删

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.8</version>
</dependency>

/**
 * 连接池基类
 *
 */
public class BaseHttpClientTest {

    protected static final int REQUEST_COUNT = 5;

    protected static final String SEPERATOR = "   ";
    
    protected static final AtomicInteger NOW_COUNT = new AtomicInteger(0);
    
    protected static final StringBuilder EVERY_REQ_COST = new StringBuilder(200);
    
    /**
     * 获取待运行的线程
     */
    protected List<Thread> getRunThreads(Runnable runnable) {
        List<Thread> tList = new ArrayList<Thread>(REQUEST_COUNT);
        
        for (int i = 0; i < REQUEST_COUNT; i++) {
            tList.add(new Thread(runnable));
        }
        
        return tList;
    }
    
    /**
     * 启动所有线程
     */
    protected void startUpAllThreads(List<Thread> tList) {
        for (Thread t : tList) {
            t.start();
            // 这里需要加一点延迟，保证请求按顺序发出去
            try {
                Thread.sleep(300);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    
    protected synchronized void addCost(long cost) {
        EVERY_REQ_COST.append(cost);
        EVERY_REQ_COST.append("ms");
        EVERY_REQ_COST.append(SEPERATOR);
    }
    
}

/**
 * 使用连接池测试
 *
 */
public class HttpclientWithPoolTest extends BaseHttpClientTest {

    private CloseableHttpClient httpClient = null;
    
    @Before
    public void before() {
        initHttpClient();
    }
    
    @Test
    public void test() throws Exception {
        startUpAllThreads(getRunThreads(new HttpThread()));
        // 等待线程运行
        for (;;);
    }
    
    private class HttpThread implements Runnable {

        @Override
        public void run() {
            HttpGet httpGet = new HttpGet("https://www.baidu.com/");
            // 长连接标识，不加也没事，HTTP1.1默认都是Connection: keep-alive的
            httpGet.addHeader("Connection", "keep-alive");
            
            long startTime = System.currentTimeMillis();
            try {
                CloseableHttpResponse response = httpClient.execute(httpGet);
                if (response != null) {
                    response.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                addCost(System.currentTimeMillis() - startTime);
                
                if (NOW_COUNT.incrementAndGet() == REQUEST_COUNT) {
                    System.out.println(EVERY_REQ_COST.toString());
                }
            }
        }
        
    }
    
    private void initHttpClient() {
        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
        // 总连接池数量
        connectionManager.setMaxTotal(1);
        // 可为每个域名设置单独的连接池数量
        connectionManager.setMaxPerRoute(new HttpRoute(new HttpHost("www.baidu.com")), 1);
        // setConnectTimeout表示设置建立连接的超时时间
        // setConnectionRequestTimeout表示从连接池中拿连接的等待超时时间
        // setSocketTimeout表示发出请求后等待对端应答的超时时间
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(1000).setConnectionRequestTimeout(2000)
                .setSocketTimeout(3000).build();
        // 重试处理器，StandardHttpRequestRetryHandler这个是官方提供的，看了下感觉比较挫，很多错误不能重试，可自己实现HttpRequestRetryHandler接口去做
        HttpRequestRetryHandler retryHandler = new StandardHttpRequestRetryHandler();
        
        httpClient = HttpClients.custom().setConnectionManager(connectionManager).setDefaultRequestConfig(requestConfig)
                .setRetryHandler(retryHandler).build();
        
        // 服务端假设关闭了连接，对客户端是不透明的，HttpClient为了缓解这一问题，在某个连接使用前会检测这个连接是否过时，如果过时则连接失效，但是这种做法会为每个请求
        // 增加一定额外开销，因此有一个定时任务专门回收长时间不活动而被判定为失效的连接，可以某种程度上解决这个问题
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                try {
                    // 关闭失效连接并从连接池中移除
                    connectionManager.closeExpiredConnections();
                    // 关闭30秒钟内不活动的连接并从连接池中移除，空闲时间从交还给连接管理器时开始
                    connectionManager.closeIdleConnections(20, TimeUnit.SECONDS);
                } catch (Throwable t) {
                    t.printStackTrace();
                }
            }
        }, 0 , 1000 * 5);
    }
    
}