CometServlet.java

package org.springboot.sample.servlet;

import java.io.IOException;
import java.util.Queue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;

import javax.servlet.AsyncContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * HTTP长连接实现
 *
 * @author 单红宇(365384722)
 * @myblog http://blog.csdn.net/catoop/
 * @create 2016年3月29日
 */
@WebServlet(urlPatterns = "/xs/cometservlet", asyncSupported = true)
//异步处理的servlet若存在过滤器，则过滤器的注解@WebFilter应设置asyncSupported=true，
//否则会报错A filter or servlet of the current chain does not support asynchronous operations.
public class CometServlet extends HttpServlet {

	private static final long serialVersionUID = -8685285401859800066L;

	private final Queue<AsyncContext> asyncContexts = new LinkedBlockingQueue<>();

	private final Thread generator = new Thread("Async Event generator") {

		@Override
		public void run() {
			while (!generator.isInterrupted()) {// 线程有效
				try {
					while (!asyncContexts.isEmpty()) {// 不为空
						TimeUnit.SECONDS.sleep(6);// 秒，模拟耗时操作
						AsyncContext asyncContext = asyncContexts.poll();
						HttpServletResponse res = (HttpServletResponse) asyncContext.getResponse();
						res.getWriter().write("{\"result\":\"OK - "+System.currentTimeMillis()+"\"}");
						res.setStatus(HttpServletResponse.SC_OK);
						res.setContentType("application/json");
						asyncContext.complete();// 完成
					}
				} catch (InterruptedException e) {
					Thread.currentThread().interrupt();
					e.printStackTrace();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}

	};
	
	@Override
	public void init() throws ServletException {
		super.init();
		generator.start();
	}

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		System.out.println(">>>>>>>>>>CometServlet Request<<<<<<<<<<<");
		doPost(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		AsyncContext asyncContext = req.startAsync();
		asyncContext.setTimeout(20 * 1000L);
		asyncContexts.offer(asyncContext);
	}

	@Override
	public void destroy() {
		super.destroy();
		generator.interrupt();
	}

	
}