Java中HttpServer (HttpsServer) ，解決response會延遲或卡住的問題

第一次使用 com.sun.net.httpserver.HttpServer 跟 com.sun.net.httpserver.HttpsServer 做為http server時，
發現連續的request會使得response卡住：

OutputStream os = httpExchange.getResponseBody();
os.write(response.getBytes()); //卡住造成阻塞，過很久才會回應，
os.close();

解決之道，就是確保connection能close, 並使用multi-thread:

final Executor multi = Executors.newFixedThreadPool(10);
final HttpServer server = HttpServer.create(new InetSocketAddress(s_HTTP_PORT), 5);
//... do your REST bindings here
server.setExecutor(multi);
server.start();

//bindings中送出Connection = close 的 header
httpExchange.getResponseHeaders().add("Connection", "close");

ref:
http://stackoverflow.com/questions/15235075/1s-delay-in-httpserver-since-java-7