/** 关闭连接池 */
 public static synchronized void shutdown() {
   logger.warn("shutdown httpClient connection pool.");
   if (client != null) {
     client.getConnectionManager().shutdown();
     IdleConnectionReaper.shutdown();
     DnsResolverHolder.shutdown();
     client = null;
   }
 }
 /**
  * Shuts down this HTTP client object, releasing any resources that might be held open. This is an
  * optional method, and callers are not expected to call it, but can if they want to explicitly
  * release any open resources. Once a client has been shutdown, it cannot be used to make more
  * requests.
  */
 public void shutdown() {
   IdleConnectionReaper.removeConnectionManager(httpClient.getConnectionManager());
   httpClient.getConnectionManager().shutdown();
 }