过滤器实栗 登录检测

摘要：项目结构代码如下登录接收内容接收内容保存返回信息用户不能为空密码不能为空报错信息为进行验证登录成功增加会话登录失败使用服务器端跳转保存数据对于登录的增加了过滤器如下首页过滤器转型因为默认的中未提供相关的方法需要向下转型获取到判断登录已经登

![](https://melovemingming-125387...
)

package com.ming.servlrt;


import com.ming.factory.DAOFactory;
import com.ming.vo.User;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String path = "login.jsp";
        // 接收userid内容
        String userid = req.getParameter("userid");
        // 接收userpass内容
        String userpadd = req.getParameter("userpass");
        // 保存返回信息
        List info = new ArrayList();
        if(userid == null || "".equals(userid)){
            info.add("用户id不能为空");
        }
        if(userpadd == null || "".equals(userpadd)){
            info.add("密码不能为空");
        }
        // 报错信息为0进行验证
        if(info.size() == 0){
            User user = new User();
            user.setUserid(userid);
            user.setPassword(userpadd);
            try{
                if(DAOFactory.getIuserDAOInstance().findLogin(user)){
                    info.add("登录成功!" + user.getName());
                    // 增加session会话
                    HttpSession session = req.getSession();
                    session.setAttribute("id", userid);
                }else{
                    info.add("登录失败");
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        // 使用服务器端跳转, 保存数据
        req.setAttribute("info", info);
        req.getRequestDispatcher(path).forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

对于登录的servlet增加了session

package com.ming.filter;

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

// 首页过滤器
public class LoginFile implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // 转型 因为默认的ServletRequest中未提供相关的方法,需要向下转型
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        // 获取到session
        HttpSession session = request.getSession();
        // 判断登录
        if(session.getAttribute("id") != null){
            // 已经登录
            filterChain.doFilter(servletRequest, servletResponse);
        }else{
            // 跳转登录页登录
            request.getRequestDispatcher("login.jsp").forward(servletRequest, servletResponse);
        }
    }

    @Override
    public void destroy() {

    }
}

  Archetype Created Web Application
    
        LoginFile
        com.ming.filter.LoginFile
    
    
        LoginFile
        /index.jsp
    
    
        login
        com.ming.servlrt.LoginServlet
    
    
        login
        /loginServlet
    

涉及 前端的js验证
采用拦截click事件

<%@ page import="java.util.List" %>
<%@ page import="java.util.Iterator" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-16
  Time: 下午11:07
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    
用户登录程序
<%
    List info = (List)request.getAttribute("info");
    if(info != null){
        Iterator iterator = info.iterator();
        while(iterator.hasNext()){
            %>
                
<%=iterator.next()%>
            <%
        }
    }
%>
    用户id 
    密码