WebSiteCounter

网站计数器三种实现方法：

第一种：使用监听器来实现。

package com.huanglei.note;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionListener {

	private int counter = 0;
	

	 public void sessionCreated(HttpSessionEvent event) {
	 counter++;
	 event.getSession().setAttribute("counter", new Integer(counter));

	 }

	 public void sessionDestroyed(HttpSessionEvent event) {
	 counter--;
	 event.getSession().setAttribute("counter", new Integer(counter));
	 }

}

 
在web.xml中配置监听器：  

  <listener>
  	<listener-class>com.huanglei.note.MyHttpSessionListener</listener-class>
  </listener>

  

在jsp页面中：

你是第${sessionScope.counter}个访问本站的用户<br>

 

 

 

第二种方法：使用过滤器。

 

package com.huanglei.note;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

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.http.HttpServletRequest;
import javax.servlet.http.HttpSession;


//导入import javax.servlet.Filter;
public class CounterFilter implements Filter {


	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) req;

		HttpSession session = request.getSession();

		 int count;
		 File file = new File("c:/count.txt");
		 if (!file.exists()) {
		 file.createNewFile();
		 }
		 BufferedReader br = new BufferedReader(new InputStreamReader(
		 new FileInputStream(file)));
		 String content = br.readLine();
		 if (content == null) {
		 count = 0;
		 } else {
		 count = Integer.parseInt(content);
		 }
		 br.close();
		 if (session.isNew()) {
		 req.setAttribute("count", new Integer(count + 1));
		 BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(
		 new FileOutputStream(file)));
		 bw.write(count + 1 + "");
		 bw.close();
		 chain.doFilter(req, res);
		 } else {
		 req.setAttribute("count", new Integer(count));
		 chain.doFilter(req, res);
		 }



	}

	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		
	}

}

 

 在web.xml中配置过滤器：  

 <filter>
 <filter-name>CounterFilter</filter-name>
 <filter-class>com.huanglei.note.CounterFilter</filter-class>
 </filter>

 

在jsp页面中：

你是第${requestScope.count}个访问本站的用户<br>

 

 

第三种方法：使用servlet

package com.huanglei.note;

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;
import javax.servlet.http.HttpSession;

public class CounterServlet extends HttpServlet {
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub		
		 response.setContentType("text/html;charset=GB18030");
		 request.setCharacterEncoding("GB18030");

		 HttpSession session = request.getSession();
		 ServletContext application = this.getServletContext();
		 Integer count = (Integer) application.getAttribute("count");
		if (count == null) {
		 count = new Integer(0);
		 }
		 int count1 = count.intValue();
		 if (session.isNew()) {
		 count1 = count.intValue()+1;
		 application.setAttribute("count", new Integer(count1));
		 }
		 response.sendRedirect("servletWebsiteCounter.jsp");

		
	}
}

 在web.xml中配置servlet：  

   <servlet>
   		<servlet-name>counterServlet</servlet-name>
   		<servlet-class>com.huanglei.note.CounterServlet</servlet-class>
   </servlet>
   <servlet-mapping>
   		<servlet-name>counterServlet</servlet-name>
   		<url-pattern>/servletWebsiteCounter</url-pattern>
   </servlet-mapping>

 

 

在jsp页面中：

你是第${applicationScope.count}个访问本站的用户<br>