摘要：項目結構代碼如下登錄接收內容接收內容保存返回信息用戶不能為空密碼不能為空報錯信息為進行驗證登錄成功增加會話登錄失敗使用服務器端跳轉保存數據對于登錄的增加了過濾器如下首頁過濾器轉型因為默認的中未提供相關的方法需要向下轉型獲取到判斷登錄已經登

![](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內容
        String userid = req.getParameter("userid");
        // 接收userpass內容
        String userpadd = req.getParameter("userpass");
        // 保存返回信息
        List info = new ArrayList();
        if(userid == null || "".equals(userid)){
            info.add("用戶id不能為空");
        }
        if(userpadd == null || "".equals(userpadd)){
            info.add("密碼不能為空");
        }
        // 報錯信息為0進行驗證
        if(info.size() == 0){
            User user = new User();
            user.setUserid(userid);
            user.setPassword(userpadd);
            try{
                if(DAOFactory.getIuserDAOInstance().findLogin(user)){
                    info.add("登錄成功!" + user.getName());
                    // 增加session會話
                    HttpSession session = req.getSession();
                    session.setAttribute("id", userid);
                }else{
                    info.add("登錄失敗");
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        // 使用服務器端跳轉, 保存數據
        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);
    }
}

對于登錄的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;

// 首頁過濾器
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 {
        // 轉型 因為默認的ServletRequest中未提供相關的方法,需要向下轉型
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        // 獲取到session
        HttpSession session = request.getSession();
        // 判斷登錄
        if(session.getAttribute("id") != null){
            // 已經登錄
            filterChain.doFilter(servletRequest, servletResponse);
        }else{
            // 跳轉登錄頁登錄
            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驗證
采用攔截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" %>


    


用戶登錄程序
<%
    List info = (List)request.getAttribute("info");
    if(info != null){
        Iterator iterator = info.iterator();
        while(iterator.hasNext()){
            %>
                
<%=iterator.next()%>
            <%
        }
    }
%>

    用戶id 
    密碼