【JavaWeb】Filter验证是否登录案例

案例分析

像我们平时访问浏览器时，经常会遇到这样的提示：

这个功能的实现很简单，下面就来具体演示一下；

代码实现

1.LoginFilter.jsp

package web.filter;

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

@WebFilter("/*")
public class LoginFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
          HttpServletRequest request=(HttpServletRequest) req;
        String uri = request.getRequestURI();//获取请求路径
        if(uri.contains("index.jsp")||uri.contains("login.jsp")||uri.contains("/css/")||uri.contains("/js/")||uri.contains("/fonts/")||uri.contains("CheckCode")){
            //访问与登录相关的页面，直接放行
            chain.doFilter(request, resp);
        }
        else {
            //与登录无关页面,查询是否登录
            Object user = request.getSession().getAttribute("user");
            if(user!=null){
                //已经登录
                chain.doFilter(request,resp);
            }
            else {
                //没有登陆
                request.setAttribute("login_msg","您尚未登陆，请先登录");
                request.getRequestDispatcher("login.jsp").forward(request,resp);
            }

        }
             
        chain.doFilter(req, resp);
    }

    public void init(FilterConfig config) throws ServletException {

    }

}