网站访问量统计案例

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源码：

AServlet.java

package one.servlet;

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;

public class AServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        ServletContext context=this.getServletContext();
        Integer count = (Integer)context.getAttribute("count");
        if(count==null){
            context.setAttribute("count", 1);
        }else{
            context.setAttribute("count", count+1);
        }
        count = (Integer)context.getAttribute("count");//重新获取count的值
        //向浏览器输出,用到响应对象！
        PrintWriter pw=response.getWriter();
        pw.print("<h1>requested count:"+count+"</h1>");//把这个数字输出到浏览器
    }
}

BServlet.java

package one.servlet;

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;

public class BServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        ServletContext context=this.getServletContext();
        Integer count = (Integer)context.getAttribute("count");
        if(count==null){
            context.setAttribute("count", 1);
        }else{
            context.setAttribute("count", count+1);
        }
        count = (Integer)context.getAttribute("count");//重新获取count的值
        //向浏览器输出,用到响应对象！
        PrintWriter pw=response.getWriter();//流
        pw.print("<h1>requested count:"+count+"</h1>");//把这个数字输出到浏览器
    }
}

不管是访问AServlet还是BServlet ，都会统计它们被请求的次数；如果关掉Tomcat（服务器），计数就会随ServletContext而死亡。