学习Servlet中的异步处理 —— Servlet3.0中的Async支持

servlet的@WebServlet注解写法：

/**
* asyncSupported属性默认是false,如果需要开启支持异步处理功能,需要设置为true
*/
@WebServlet(name = "ServletAsyn", urlPatterns = "/ServletAsyn", asyncSupported = true)

AsynFilter的@WebServlet注解写法：

@WebFilter(filterName="AsynFilter",asyncSupported=true,value={"/ServletAsyn"},dispatcherTypes={DispatcherType.REQUEST,DispatcherType.ASYNC})

测试过程:

打开浏览器输入项目servlet地址: http://localhost:8080/ServletAsynFilter/ServletAsyn

总结：

package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;

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

/**
* autor:xanwidtf@foxmail.com
*/
/**
* Servlet implementation class ServletAsyn
*/
@WebServlet(name = "ServletAsyn", urlPatterns = "/ServletAsyn", asyncSupported = true)
public class ServletAsyn extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#HttpServlet()
*/
public ServletAsyn() {
super();
}

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//response.getWriter().append("Served at: ").append(request.getContextPath());

System.out.println("Servlet执行开始时间："+new Date());
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
Date date = new Date(System.currentTimeMillis());
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
out.print("<h1>");
out.println("Servlet  begin --" + sdf.format(date) + "<br>");// 响应输出到客户端
out.print("</h1>");
out.print("<hr>");

/*
* 体现异步思想，Servlet执行结束，而异步的线程仍然在继续跑
*/
AsyncContext context=request.startAsync();
new Thread(new Executor(context)).start(); //new Thread 传递AsyncContext对象   并且start
System.out.println("Servlet执行结束时间："+new Date());
}

//内部类实现线程
public class Executor implements Runnable{
private AsyncContext context;
public Executor(AsyncContext context){
this.context=context;
}

@Override
public void run() {
//执行相关复杂业务
try {
Thread.sleep(1000*3);
context.getRequest();
context.getResponse();
ServletResponse response = context.getResponse();
PrintWriter out = response.getWriter();
Date date = new Date(System.currentTimeMillis());
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");

out.print("<h1>");
out.println("Thread worker finished --"+ sdf.format(date));// 响应输出到客户端
out.print("</h1><hr>");
out.flush();
System.out.println("业务完成时间:"+new Date());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}

}

package Filter;

import java.io.IOException;

import javax.servlet.DispatcherType;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;

@WebFilter(filterName="AsynFilter",asyncSupported=true,value={"/ServletAsyn"},dispatcherTypes={DispatcherType.REQUEST,DispatcherType.ASYNC})public class AsynFilter implements Filter {

@Override
public void destroy() {

}

@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
throws IOException, ServletException {
System.out.println("Start.....AsynFilter");
arg2.doFilter(arg0, arg1);
System.out.println("End....AsynFilter");
}

@Override
public void init(FilterConfig arg0) throws ServletException {

}

}