• 监听器与过滤器练习

    文章目录

    监听器与过滤器练习

    题目：

    实现某电商系统的字符过滤器，要求对所有页面进行字符过滤功能。

    选取合适的监听器实现统计商品列表页的访问人数（注：同一用户多次访问商品列表页时，计数为1次）。

    提交代码要求如下：

    1）提交商品列表页的关键代码；DealServlet

    显示商品列表页的访问人数

    2）提交字符过滤器的关键代码；

    3） 提交相关监听器的关键代码；

    代码如下：

    login.html

    <!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

<h1>商品列表</h1>
<a href="d1">点我查看网页访问量</a>
</body>
</html>

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    ContextListener

    package listener;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

/**
 * Application Lifecycle Listener implementation class ContextListener
 *
 */
@WebListener
public class ContextListener implements ServletContextListener {

    /**
     * Default constructor. 
     */
    public ContextListener() {
        // TODO Auto-generated constructor stub
    }

	/**
     * @see ServletContextListener#contextDestroyed(ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent sce)  { 
         // TODO Auto-generated method stub
    }

	/**
     * @see ServletContextListener#contextInitialized(ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent sce)  { 
         // TODO Auto-generated method stub
    	ServletContext context=sce.getServletContext();
    	context.setAttribute("userNum", 0);
    }
	
}

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    PageListener

    package listener;

import javax.servlet.ServletContext;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/**
 * Application Lifecycle Listener implementation class PageListener
 *
 */
@WebListener
public class PageListener implements HttpSessionListener {

    /**
     * Default constructor. 
     */
    public PageListener() {
        // TODO Auto-generated constructor stub
    }

	/**
     * @see HttpSessionListener#sessionCreated(HttpSessionEvent)
     */
    public void sessionCreated(HttpSessionEvent se)  { 
         // TODO Auto-generated method stub
    	System.out.println("Session创建-------------------");
    	ServletContext context=se.getSession().getServletContext();
    	int count=(int)context.getAttribute("userNum");
    	count++;
    	context.setAttribute("userNum", count);
    	
    }

	/**
     * @see HttpSessionListener#sessionDestroyed(HttpSessionEvent)
     */
    public void sessionDestroyed(HttpSessionEvent se)  { 
         // TODO Auto-generated method stub
//    	System.out.println("Session销毁-------------------");
//    	ServletContext context=se.getSession().getServletContext();
//    	int count=(int)context.getAttribute("userNum");
//    	count--;
//    	context.setAttribute("userNum", count);
    }
	
}

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    DealServlet

    package servlet;

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;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class DealServlet
 */
@WebServlet("/d1")
public class DealServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DealServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
		PrintWriter writer=response.getWriter();
		HttpSession session=request.getSession();
		ServletContext context=getServletContext();
		int count = (int)context.getAttribute("userNum");
		writer.write("<h1>访问人数为：</h1>"+count);
	}

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

}

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    CharacterFilter

    package filter;

import java.io.IOException;
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.annotation.WebFilter;

/**
 * Servlet Filter implementation class CharacterFilter
 */
@WebFilter("/*")
public class CharacterFilter implements Filter {

    /**
     * Default constructor. 
     */
    public CharacterFilter() {
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {
		// TODO Auto-generated method stub
	}

	/**
	 * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
	 */
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		// place your code here

		request.setCharacterEncoding("utf-8");
		
		response.setContentType("text/html;charset=utf-8");
		// pass the request along the filter chain
		chain.doFilter(request, response);
	}

	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig fConfig) throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("Filter is initing!");
	}

}


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  • 原文地址：https://blog.csdn.net/huayu8086/article/details/125561015