DemoAsync3Action.java

DemoAsync3Action.java

package com.servlet3.demo;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

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

/**
 * Servlet中添加异步支持
 * 
 * @author yongboy
 * @time 2012-1-17
 * @version 1.0
 */
@WebServlet(urlPatterns = "/async3")
public class DemoAsync3Action extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private final ExecutorService executor;

	{
		executor = Executors.newCachedThreadPool(new ThreadFactory() {
			public Thread newThread(Runnable r) {
				Thread thread = new Thread(r);
				thread.setName("DemoAsyncAction3 executor Thread "
						+ thread.getId());
				thread.setPriority(Thread.MAX_PRIORITY);

				return thread;
			}
		});

		if (executor instanceof ThreadPoolExecutor) {
			// 不超过服务器CPU数目个线程较佳
			((ThreadPoolExecutor) executor).setMaximumPoolSize(Runtime
					.getRuntime().availableProcessors());
		}
	}

	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// 添加此属性，告诉浏览器，需要分段显示
		response.setHeader("Connection", "Keep-Alive");
		response.setContentType("text/html;charset=UTF-8");
		final PrintWriter out = response.getWriter();

		output(out, "the manual async start ...");

		Future<?> future = executor.submit(new Runnable() {
			@Override
			public void run() {
				try {
					// 假设实际业务耗时10秒
					Thread.sleep(10000L);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}

				try {
					output(out, "the manual async goes here ...");
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		});

		boolean result = false;
		try {
			// 在此处，会阻塞当前线程，直到超时或线程执行完毕...
			future.get(10L, TimeUnit.SECONDS);
			result = true;
		} catch (InterruptedException e) {
			e.printStackTrace();
		} catch (ExecutionException e) {
			e.printStackTrace();
		} catch (TimeoutException e) {
			e.printStackTrace();
		} finally {
			future.cancel(true);
		}

		if (result) {
			output(out, "the manual async is ok ...");
		} else {
			output(out, "the manual async is failure ...");
		}

		// 按照顺序输出到此，结束请求
		output(out, "the end of manual async ...");
		out.close();
	}

	private static void output(PrintWriter out, String message)
			throws IOException {
		out.println(message);
		out.flush();
	}
}