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一个servlet例子-统计网站访问量

2018-03-26 00:33 399 查看

1.创建JavaWeb项目，名WebCount
2.修改web.xml，如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>WebCount1</display-name>
<servlet>
    <servlet-name>CounterServlet</servlet-name>
    <servlet-class>com.CounterServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>CounterServlet</servlet-name>
    <url-pattern>/counter</url-pattern>
</servlet-mapping>
<welcome-file-list>
    <welcome-file>counter</welcome-file>
</welcome-file-list>

</web-app>、
3.新建名称为CounterServlet的servlet类，在该类dopost（）方法中实现统计访问数目。

package com;

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 CounterServlet
*/
@WebServlet("/CounterServlet")
public class CounterServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public CounterServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

   /**
   * @see Servlet#destroy()
   */
   public void destroy() {
       super.destroy();
   }

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

   /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       //获得ServletContext对象
       ServletContext context=getServletContext();
       //从ServletContext中获取计数器对象
       Integer count=(Integer) context.getAttribute("counter");
       if(count==null){//如果为空，则在ServletContext中设置一个计数器的属性
           count=1;
           context.setAttribute("counter", count);
       }else{
           context.setAttribute("counter", count+1);
       }

       response.setContentType("text/html");//响应正文的MIME类型
       response.setCharacterEncoding("UTF-8");//响应的编码格式
       PrintWriter out=response.getWriter();
//       out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
//       out.println("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
//       out.println("<HTML>");
       out.println("<HEAD><TITLE>统计网站访问次数</TITLE></HEAD>");
       out.println("<BODY>");
//       out.println("<h2><font color='gray'");
       out.println("您是第"+context.getAttribute("counter")+"位访客！");
//       out.println("</font>");
//       out.println("</h2>");
       out.println("</BODY>");
       out.println("</HTML>");
       out.flush();
       out.close();
   }

}

4.将项目部署到服务器，启动服务器。结果如下。

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