ServletContext对象统计在线人数

package com.zdsofe.servlet1;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletContext;

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 implementation class CountVisited

 */

@WebServlet("/CountVisited")

public class CountVisited extends HttpServlet {

    private static final long serialVersionUID = 1L;

    /**

     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

     */

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //编码格式

        response.setCharacterEncoding("utf-8");

        response.setContentType("text/html;charset=utf-8");

        //输出流

        PrintWriter out=response.getWriter();

        //获得上下文环境

        ServletContext context=    request.getServletContext();

        //获取访问人数

        Integer value=(Integer)context.getAttribute("count");

        //定义访问人数变量

        int count=1;

        if(value==null)

        {

            out.write("你是第一个访问者");

        }

        else

        {

            count+=value;

        }

        context.setAttribute("count", count);

        //统计人数

        out.print(count);

        //刷新流

        out.flush();

        //关闭流

        out.close();

    }

    /**

     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

     */

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

通过此路径在浏览器上访问  http://localhost:8080/webProject1/CountVisited