Apache HttpClient4.5（三）

来源：互联网发布：淘宝如何做展现词编辑：程序博客网时间：2024/05/16 11:15

转载自：
http://blog.csdn.net/z69183787/article/details/78039601
http://blog.csdn.net/z69183787/article/details/77964021

HttpClient中的RequestConfig在使用时：

RequestConfig requestConfig = RequestConfig.custom()    .setConnectionRequestTimeout(1000)          .setSocketTimeout(1000)    .setConnectTimeout(1000)    .build();

有三个超时：connectionRequestTimeout、connectTimeout、socketTimeout，它们各自含义：
connectTimeOut：指建立连接的超时时间；
connectionRequestTimeOut：指从连接池获取到连接的超时时间，如果是非连接池的话，该参数暂时没有发现有什么用处。
socketTimeOut：指客户端和服务进行数据交互的时间，是指两者之间如果两个数据包之间的时间大于该时间则认为超时，而不是整个交互的整体时间，比如如果设置1秒超时，如果每隔0.8秒传输一次数据，传输10次，总共8秒，这样是不超时的。而如果任意两个数据包之间的时间超过了1秒，则超时。

更深理解可以参照:http://www.baeldung.com/httpclient-connection-management

RetryHandler重试方式ServiceUnavailableRetryStrategy并且可以自定义retry时间的间隔：

public static CloseableHttpClient getHttpClient() {        ServiceUnavailableRetryStrategy serviceUnavailableRetryStrategy = new ServiceUnavailableRetryStrategy() {            /**             * retry逻辑             */            @Override            public boolean retryRequest(HttpResponse response, int executionCount, HttpContext context) {                if (executionCount <= 3)                    return true;                else                    return false;            }            /**             * retry间隔时间             */            @Override            public long getRetryInterval() {                return 2000;            }        };        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();        cm.setMaxTotal(MAX_TOTAL);        cm.setDefaultMaxPerRoute(MAX_PERROUTE);        CloseableHttpClient httpClient = HttpClients.custom().setRetryHandler(new DefaultHttpRequestRetryHandler())                .setConnectionManager(cm).build();        return httpClient;    }

除此之外，还有StandardHttpRequestRetryHandler、DefaultHttpRequestRetryHandler，或则自定义，实现HttpRequestRetryHandler即可。

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。
httpclient的连接池中只有一个httpclient的实例，可以看看CloseableHttpClient和PoolingHttpClientConnectionManager的源码,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，具体看源码。
简单示例：

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);    }    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;    }    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<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();        }    }    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();            }        }    }    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" };        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;        }        @Override        public void run() {            try {                System.out.println(HttpClientUtil.get(url));            } finally {                countDownLatch.countDown();            }        }    }}

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