Filter-案例-登录验证

package com.itheima.web.Filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import java.io.IOException;
/*
* 登陆验证的过滤器
* */
@WebFilter("/*")
public class LoginFilter implements Filter {
    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        //先把接收到的req强转成HttpServletRequest格式的，不然获取不了Session对象
        HttpServletRequest request = (HttpServletRequest) req;

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

        //获取当前路径资源
        String url = request.getRequestURL().toString();

        //循环判断
        for (String u : urls) {
            if (url.contains(u)){//contains包含
                //找到了
                //放行
                chain.doFilter(req,resp);
                //结束方法
                return;
            }
        }

        //1. 获取到session对象中的user数据
        HttpSession session = request.getSession();
        Object user = session.getAttribute("user");

        //2. 判断session中是否有user
        if (user != null){
            //登录过了
            //放行
        }else {
            //没有登录，储存提示信息，跳转到登录页面
            request.setAttribute("login_msg","您尚未登陆！");
            request.getRequestDispatcher("/login.jsp").forward(req,resp);
        }
        //放行
        chain.doFilter(req, resp);
    }

    public void destroy() {
    }

    public void init(FilterConfig config) throws ServletException {

    }

}