Servlet----------用servlet写一个“网站访问量统计“的小案例

 package cn.example;

 import java.io.IOException;
 import java.io.PrintWriter;

 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 /**
  * 网站访问量统计小案例
  * @author LZC
  */
 public class CallCount extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         /*
          *1、获取ServletContext对象
          *2、从ServletContext对象中获取名为count的属性用来保存访问量
          *3、如果存在，则保存回去
          *4、如果不存在，说明是第一次访问，向ServletContext中保存名为count的属性，值 为1
          */
         response.setCharacterEncoding("GBK");
         ServletContext application =this.getServletContext();
         Integer count = (Integer) application.getAttribute("count");
         if(count==null){
             application.setAttribute("count", 1);
         }else{
             application.setAttribute("count", count+1);
         }

          // 向浏览器输出，需要使用响应请求
         response.setContentType("text/html");
         PrintWriter out = response.getWriter();
         out.println("<h2>您一共访问了 "+count+" 次</h2>");
     }
 }