HttpClient4 TIME_WAIT和CLOSE_WAIT

值 得一说的是，对于基于TCP的HTTP协议，关闭TCP连接的是Server端，这样，Server端会进入TIME_WAIT状态，可 想而知，对于访 问量大的Web Server，会存在大量的TIME_WAIT状态，假如server一秒钟接收1000个请求，那么就会积压 240*1000=240，000个 TIME_WAIT的记录，维护这些状态给Server带来负担。当然现代操作系统都会用快速的查找算法来管理这些 TIME_WAIT，所以对于新的 TCP连接请求，判断是否hit中一个TIME_WAIT不会太费时间，但是有这么多状态要维护总是不好。  
HTTP协议1.1版规定default行为是Keep-Alive，也就是会重用TCP连接传输多个 request/response，一个主要原因就是发现了这个问题。  

public class HttpApacheClient {

    private static class SingletonHandler{
        private static HttpApacheClient singleton = new HttpApacheClient();
    }

    private HttpApacheClient(){}

    public static HttpApacheClient getInstance(){
        return SingletonHandler.singleton;
    }

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



    private final HttpClientConnectionManager manager = builderPoolConnectionManager() ;  //定义连接池管理变量
    ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
        @Override
        public String handleResponse(final HttpResponse response)
                throws ClientProtocolException, IOException {
            int status = response.getStatusLine().getStatusCode();
            if (status >= 200 && status < 300) {
                HttpEntity entity = response.getEntity();
                if (entity == null) throw new BusinessException(RESULT_LOG_ERROR);
                String content =  EntityUtils.toString(entity);
                logger.info("the log back :"+content);
                JSONObject jsonObject = JSON.parseObject(content);
                Integer returnStatus = (Integer)jsonObject.get("status");
                if (returnStatus !=200) throw new BusinessException(RESULT_LOG_ERROR,content);
                return content;
            } else {
                throw new ClientProtocolException("Unexpected response status: " + status);
            }
        }
    };


    public HttpClientConnectionManager builderPoolConnectionManager(){
        final SSLContext context = SSLContexts.createSystemDefault();
        final HostnameVerifier verifier = new DefaultHostnameVerifier() ;
        //自定义注册器，既可以发送http请求，也可以发送https请求
        final Registry<ConnectionSocketFactory> register = RegistryBuilder.<ConnectionSocketFactory>create()
                .register("http" , PlainConnectionSocketFactory.INSTANCE)
                .register("https" , new SSLConnectionSocketFactory(context ,verifier))
                .build() ;
        PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager(register);
        poolingHttpClientConnectionManager.setMaxTotal(200);  //设置连接池的最大连接数
        poolingHttpClientConnectionManager.setDefaultMaxPerRoute(poolingHttpClientConnectionManager.getMaxTotal());  //一个路由的最大连接数
        return poolingHttpClientConnectionManager ;
    }

    public HttpClient buildHttpClient(){
        RequestConfig config = RequestConfig.custom()
                .setConnectionRequestTimeout(3000)  //从池中获取请求的时间
                .setConnectTimeout(2000)   //连接到服务器的时间
                .setSocketTimeout(5000).build(); //读取信息时间

        CloseableHttpClient build = HttpClients.custom()
                .setRetryHandler(DefaultHttpRequestRetryHandler.INSTANCE)
                .setDefaultRequestConfig(config)
                .setConnectionManagerShared(true)
                .setConnectionManager(manager)
                .build();
        return build ;
    }

    public static String postJson(String url, List<NameValuePair> params) throws Exception {
        String urlHead = (String) BeanHelper.getConfig("url");
        url = urlHead+url;
        logger.info("url "+url+";"+params);
        HttpApacheClient utils = getInstance();
        HttpClient httpClient = null;
        HttpPost httpPost = null;
        try {
            httpClient = utils.buildHttpClient();
            httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params,"UTF-8"));
            httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");
            return httpClient.execute(httpPost, utils.responseHandler);
        }catch (Exception e){
            if (httpPost!=null) httpPost.abort();//异常时 关闭连接
            throw  e;
        }
    }

    }
}