JavaWeb-过滤器、监听器常见应用

一、过滤器、监听器常见应用

监听器：GUI编程中经常使用；

package com.kuang.filter;

import java.awt.*;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

public class TestPanel {

	public static void main(String[] args) {
		Frame frame = new Frame("中秋节快乐");	// 新建一个窗体
		Panel panel = new Panel(null);	// 面板
		frame.setLayout(null);	// 设置窗体的布局
		
		frame.setBounds(300,300,500,500); // 窗体坐标和宽高
		frame.setBackground(new Color(0,0,255)); // 设置背景颜色
		
		panel.setBounds(50,50,300,300); // 面板坐标和宽高
		panel.setBackground(new Color(0,255,0)); // 设置背景颜色
		
		frame.add(panel); // 把面板添加到窗体上
		
		frame.setVisible(true); // 设置窗体为可见性
		
		// 监听事件，监听关闭事件
		frame.addWindowListener(new WindowListener() {
			
			public void windowOpened(WindowEvent arg0) {
				// TODO Auto-generated method stub
				System.out.println("打开");
			}
			
			public void windowIconified(WindowEvent arg0) {
				// TODO Auto-generated method stub
				
			}
			
			public void windowDeiconified(WindowEvent arg0) {
				// TODO Auto-generated method stub
				
			}
			
			public void windowDeactivated(WindowEvent arg0) {
				// TODO Auto-generated method stub
				System.out.println("未激活");
			}
			
			public void windowClosing(WindowEvent arg0) {
				// TODO Auto-generated method stub
				System.out.println("关闭ing");
				// 有 0和 1
				System.exit(0);
				
			}
			
			public void windowClosed(WindowEvent arg0) {
				// TODO Auto-generated method stub
				System.out.println("关闭ed");
			}
			
			public void windowActivated(WindowEvent arg0) {
				// TODO Auto-generated method stub
				System.out.println("激活");
			}
		});
	}
}

用户登录之后才能进入主页！用户注销后就不能进入主页了！

登录页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>登录</h1>
        <!-- 地址前面需要加上项目名 -->
<form action="/javaweb-filter/servlet/login" method="post">
    <input type="text" name="username">
    <input type="submit">
</form>

</body>
</html>

验证用户登录密码

package com.kuang.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.kuang.util.Constant;

// 登录页面
public class LoginServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        // 获取前端请求的参数
        String username = req.getParameter("username");
        System.out.println("aaa: --------------------> "+username);
        if (username.equals("admin")) { // 登录成功
            req.getSession().setAttribute(Constant.USER_SESSION, req.getSession().getId());
            resp.sendRedirect("/javaweb-filter/sys/success.jsp");
        }else { // 登录失败
            resp.sendRedirect("/javaweb-filter/error.jsp");
        }
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("123");
        // TODO Auto-generated method stub
        doGet(req, resp);
    }
}

登录成功

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

<h1>主页</h1>

<p><a href="/javaweb-filter/servlet/logout">注销</a></p>
</body>
</html>

登录失败

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

<h1>错误</h1>
<p><a href="/javaweb-filter/index.jsp">返回登录页面</a></p>

</body>
</html>

过滤器

package com.kuang.filter;

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.kuang.util.Constant;


// 让用户不输入密码不能进入主页
public class SysFilter implements Filter{

    public void init(FilterConfig filterConfig) throws ServletException {
    }
    
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        // 把 ServletRequest强制转换成  HttpServletRequest
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        
        if (request.getSession().getAttribute(Constant.USER_SESSION)==null) {
            // 注意：/javaweb-filter/ 项目名前面必须要有 /，否则会循环重定向不会停下来
            response.sendRedirect("/javaweb-filter/error.jsp");
        }
        
        chain.doFilter(request,response);
    }

    public void destroy() {

    }
}

用户注销

package com.kuang.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.kuang.util.Constant;

// 注销页面代码
public class LogoutServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Object user_session = req.getSession().getAttribute(Constant.USER_SESSION);
        if(user_session != null) {
            req.getSession().removeAttribute(Constant.USER_SESSION);
            resp.sendRedirect("/javaweb-filter/index.jsp");
        } else {
            resp.sendRedirect("/javaweb-filter/index.jsp");
        }
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
    doGet(req, resp);
    }
}

提取此项目中的变量名

package com.kuang.util;

public class Constant {
    // 用于提取项目中的变量名
    public final static String USER_SESSION = "USER_SESSION";

}

web.xml配置

<?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_2_5.xsd"
	version="2.5">
	<display-name>javaweb-filter</display-name>
	<welcome-file-list>
		<welcome-file>index.html</welcome-file>
		<welcome-file>index.htm</welcome-file>
		<welcome-file>index.jsp</welcome-file>
		<welcome-file>default.html</welcome-file>
		<welcome-file>default.htm</welcome-file>
		<welcome-file>default.jsp</welcome-file>
	</welcome-file-list>
	
    <!-- 映射登录页面 -->
	<servlet>
		<servlet-name>LoginServlet</servlet-name>
		<servlet-class>com.kuang.servlet.LoginServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>LoginServlet</servlet-name>
		<url-pattern>/servlet/login</url-pattern>
	</servlet-mapping>

    <!-- 映射注销页面 -->
	<servlet>
		<servlet-name>LogoutServlet</servlet-name>
		<servlet-class>com.kuang.servlet.LogoutServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>LogoutServlet</servlet-name>
		<url-pattern>/servlet/logout</url-pattern>
	</servlet-mapping>
	
    <!-- 映射过滤器 -->
	<filter>
		<filter-name>SysFilter</filter-name>
		<filter-class>com.kuang.servlet.SysFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>SysFilter</filter-name>
		<url-pattern>/sys/*</url-pattern>
	</filter-mapping>
</web-app>

posted @ 2021-02-21 09:49 魍阅读(69) 评论(0) 收藏举报

刷新页面返回顶部

JavaWeb-过滤器、监听器常见应用

一、过滤器、监听器常见应用

公告