Filter&&Listener-优快云博客

一、Filter快速入门

二、Filter的执行流程

三、Filter使用细节

3.1 Filter拦截路径配置

3.2 过滤器链

四、案例——登录验证

package com.itheima.web.fiter;

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


/**
 * 登录验证的过滤器
 */
@WebFilter( "/*")
public class LoginFilter implements Filter {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {

        //判断访问资源路径是否和登录注册相关
        String[] urls = {"/login.jsp","/imgs/","/css/","/loginServlet","/register.jsp","/register","/checkCodeServlet"};

        HttpServletRequest req = (HttpServletRequest) request;

        //获取当前访问的资源路径
        String url = req.getRequestURL().toString();

        //循环判断iter
        for (String u : urls) {
            if (url.contains(u)){
                //找到了
                //放行
                chain.doFilter(request, response);
                return;
            }
        }


        //1.判断session中是否有user对象
        HttpSession session = req.getSession();
        Object user = session.getAttribute("user");

        //2.判断user是否为Null
        if (user != null){
            //登陆过
            //放行
            chain.doFilter(request, response);
        }else{
            //没有登录，存储提示信息，拦截，并跳转到登陆界面
            req.setAttribute("login_msg", "您尚未登录！");
            req.getRequestDispatcher("/login.jsp").forward(request, response);

        }


    }

    public void init(FilterConfig config) throws ServletException {
    }

    public void destroy() {
    }


}