JavaWeb19.5【Filter&Listener：案例1-登录验证】

基于day17_base项目

 

 

 

 

package com.haifei.web.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

/**
 * 用户登录验证的过滤器
 */
@WebFilter("/*")
public class LoginFilter implements Filter {
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        //1 强转转换
        HttpServletRequest request = (HttpServletRequest)req;

        //2 获取资源请求路径
        String uri = request.getRequestURI();

        //3 判断是否包含登录相关资源，注意也要排除掉css/js/图片/验证码等资源
        if (uri.contains("/login.jsp") || uri.contains("/LoginServlet") || uri.contains("/CheckCodeServlet") || uri.contains("/css/") || uri.contains("/js/") || uri.contains("/fonts/")){
            //包含 --> 用户欲登录 --> 放行
            chain.doFilter(req, resp);
        }else {
            //不包含 --> 判断用户是否已登录

            //4 从session中获取user
            Object user = request.getSession().getAttribute("user");
            if (user != null){
                //已登录 --> 放行
                chain.doFilter(req, resp);
            }else {
                //未登录 --> 跳转到登录页面
                request.setAttribute("login_msg", "您尚未登录，请登录！");
                request.getRequestDispatcher("/login.jsp").forward(request, resp);
            }
        }
    }

    public void init(FilterConfig config) throws ServletException {

    }

    public void destroy() {

    }

}