需求：有一个首页，首页中有登录和注册 1. 点击注册进入注册页面。成功注册后，在页面中显示 “恭喜您，注册成功，页面内将在5秒后跳转到个人主页，点击这里立即跳转” 。进入个人主页后显示当前的时间。

1.项目所需的jar包

1. 导包：c3p0包、dbut ils包、servlet包，c3p0依赖包以及c3p0文件配置。
2. 创建一个数据库day0914，并创建一个表user用于数据的存储。
3. 数据库相关的包和类JdbcUtils。

2. 项目总览

3. 对外提供连接池对象

package com.fy.utils;
//1. 对外提供连接池对象
import com.mchange.v2.c3p0.ComboPooledDataSource;

import javax.sql.DataSource;

public class JdbcUtils {
    
    
    //创建连接池对象，与数据库建立连接，并返回
    private static DataSource ds = new ComboPooledDataSource("myc3p0");
    //对外提供创建的连接池ds
    public static DataSource getDataSource(){
    
    
        return ds;
    }
}

4. 实体类

package com.fy.domain;

import java.text.SimpleDateFormat;
import java.util.Date;

//2. 实体类
public class User {
    
    

    private int id;
    private String username;
    private String password;
    private Date lastTime;
    //无参构造函数
    public User() {
    
    
        super();
    }
    //全参构造函数
    public User(int id, String username, String password, Date lastTime) {
    
    
        super();
        this.id = id;
        this.username = username;
        this.password = password;
        this.lastTime = lastTime;
    }

    public int getId() {
    
    
        return id;
    }

    public void setId(int id) {
    
    
        this.id = id;
    }

    public String getUsername() {
    
    
        return username;
    }

     public void setUsername(String username) {
    
    
        this.username = username;
    }

    public String getPassword() {
    
    
        return password;
    }

    public void setPassword(String password) {
    
    
        this.password = password;
    }

    public Date getLastTime() {
    
    
        return lastTime;
    }

    public void setLastTime(Date lastTime) {
    
    
        this.lastTime = lastTime;
    }

    public String getRegister() throws Exception{
    
    
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return sdf.format(lastTime);
    }

    @Override
    public String toString() {
    
    
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", lastTime=" + lastTime + "]";
    }

}

5. 定义接口，完成登录注册功能

package com.fy.dao;
//3. 定义接口一个：UserDao，完成登录注册功能
        import com.fy.domain.User;
//创建接口
public interface UserDao {
    
    
    //接口中定义用户登录方法
    User login(User u) throws Exception;
    //接口中定义用户注册方法,返回int值
    int register(User u) throws Exception;
    //接口中定义用户的注册登录时间方法，通过重写方法，进行时间的更新
    void updateLastTime(User u,String lastTime) throws Exception;

}

6. 重写接口中的方法，功能实现

package com.fy.service;

import com.fy.dao.UserDao;
import com.fy.domain.User;
import com.fy.utils.JdbcUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
//4. 重写接口中的方法，功能实现
public class UserService implements UserDao {
    
    

    @Override
    public User login(User u) throws Exception{
    
    
        //建立连接池
        QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
        //编写SQL语句，
        String sql = "select id,username,password,last_time as lastTime from user where username = ? and password = ?";
        //获得数据库中的数据
        return qr.query(sql,new BeanHandler<User>(User.class),u.getUsername(),u.getPassword());
    }

    @Override
    public int register(User u) throws Exception{
    
    
        QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
        //在数据库中插入数据
        String sql = "insert into user values (null,?,?,?)";
        //对象qr将用户名、密码和注册信息在到数据库中更新
        return qr.update(sql,u.getUsername(),u.getPassword(),u.getRegister());
    }

    @Override
    public void updateLastTime(User u, String lastTime) throws Exception {
    
    
        QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
        //更新时间
        String sql = "update user set last_time = ? where username = ?";
        qr.update(sql,lastTime,u.getUsername());
    }

}

7. 前端首页

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2020/9/14
  Time: 19:57
  To change this template use File | Settings | File Templates.
--%>
<%--
      5. 首页
         <%= request.getContextPath()%>：
            页面间的跳转
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <h1>首页</h1>

  <a href="<%= request.getContextPath()%>/register.jsp">请注册</a>
  <a href="<%= request.getContextPath()%>/login.jsp">请登录</a>

  </body>
</html>

8. 前端登录页面

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2020/9/15
  Time: 13:48
  To change this template use File | Settings | File Templates.
--%>
<%--
      6. 登录页面
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>登录页面</h1>

<form action="<%= request.getContextPath()%>/login" method="post">

    <input type="text" name="user"> <span style="color:red"><%= request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error")%></span>
    <br>
    <input type="password" name="pwd">
    <br>
    <input type="submit" value="登录">
    <br>

</form>
</body>
</html>

9. 前端注册页面

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2020/9/15
  Time: 13:51
  To change this template use File | Settings | File Templates.
--%>

<%--
        7. 注册页面
--%>


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>注册页面</h1>

<form action="<%= request.getContextPath()%>/register" method="post">

    <input type="text" name="user"><br>
    <input type="password" name="pwd"><br>
    <input type="submit" value="注册"><br>

</form>

</body>
</html>

10. 创建服务器，获取用户提交的数据

package com.fy.servlet;

import com.fy.domain.User;
import com.fy.service.UserService;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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.Date;
//8. 创建服务器，获取用户提交的数据
@WebServlet("/register")
public class RegisterServlet extends HttpServlet {
    
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //修改编码格式
        request.setCharacterEncoding("utf-8");
        //获取用户提交的数据
        UserService service = new UserService();
        //单独获取username , password,并将用户名和密码封装成一个对象
        String username = request.getParameter("user");
        String password = request.getParameter("pwd");
        //创建用户对象u
        User u = new User(0, username, password, new Date());
        int row = 0;
        try {
    
    
            row = service.register(u);
        } catch (Exception e) {
    
    
            e.printStackTrace();
        }
        if(row != 0){
    
    
            //user对象初始化
            User user = null;
            try {
    
    
                user = service.login(u);
            } catch (Exception e) {
    
    
                e.printStackTrace();
            }
            HttpSession session = request.getSession();
            session.setAttribute("user", user);
            session.setAttribute("tag", "register");
            response.sendRedirect(request.getContextPath()+"/success.jsp");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        doGet(request, response);
    }

}

11. 前端注册成功后的跳转页面

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2020/9/15
  Time: 13:52
  To change this template use File | Settings | File Templates.
--%>

<%--
        9. 注册成功后的跳转页面
--%>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <script type="text/javascript">
        //页面加载时，进行倒数
        onload = function(){
     
     
            //获得倒数的动作
            var sp = document.getElementById("sp");
            var count = 5;
            setInterval(function(){
     
     
                //设置值
                sp.innerText = --count;
                if(count == 1){
     
     
                    location.href = "<%= request.getContextPath()%>/home.jsp";
                }
            },1000);
        }

    </script>
</head>
<body>
    恭喜您，注册成功，将在<span id="sp">5</span>秒后跳转到个人主页，点击<a href="<%= request.getContextPath()%>/home.jsp">这里</a>立即跳转
</body>
</html>

12. 前端个人主页

<%@ page import="com.fy.domain.User" %>
<%@ page import="com.sun.xml.internal.messaging.saaj.soap.ver1_1.Header1_1Impl" %><%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2020/9/15
  Time: 13:41
  To change this template use File | Settings | File Templates.
--%>
<%--
        10. 个人主页
--%>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<%

    User u = (User)session.getAttribute("user");
    if (u == null) {
        request.setAttribute("login_error", "您还未登录，请先登录");
        request.getRequestDispatcher("/login.jsp").forward(request, response);
    }
%>
<h1>个人主页</h1>
欢迎您，
<c:if test="${ tag == 'register' }">
    <%= ((User)session.getAttribute("user")).getUsername() %>，这是您的首次登录
</c:if>
<c:if test="${ tag == 'login' }">
    <%= ((User)session.getAttribute("user")).getUsername() %>，您上次登录的时间是：<%= ((User)session.getAttribute("user")).getLastTime() %>
</c:if>
<br>
退出登录

</body>
</html>

13. 创建login服务器，将获取的用户名和密码确定用户是否存在，判断是否登录成功

package com.fy.servlet;

import com.fy.domain.User;
import com.fy.service.UserService;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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.text.SimpleDateFormat;
import java.util.Date;


//11. 创建login服务器，将获取的用户名和密码确定用户是否存在，判断是否登录成功

/**
 * 做法：
 *      1. 先拿着用户名去查对应的时间，查不到就结束，查得到就获取这个时间（老时间）【开启事物】
 *      2. 再设置现在的时间（新时间），再拿着用户名和密码去登录
 *      3. 登录失败【回滚事务】结束，成功【提交事务】就跳转到主页
 */

@WebServlet("/login")
public class LoginServlet extends HttpServlet {
    
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    

        request.setCharacterEncoding("utf-8");
        UserService service = new UserService();

        String username = request.getParameter("user");
        String password = request.getParameter("pwd");
        User u = new User(0, username, password, null);

        User user = null;
        try {
    
    
            user = service.login(u);
            System.out.println(user);
        } catch (Exception e) {
    
    
            e.printStackTrace();
        }
        HttpSession session = request.getSession();
        if(user != null){
    
    
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            String lastTime = sdf.format(new Date());
            try {
    
    

                service.updateLastTime(user, lastTime);
                session.setAttribute("user", user);
                session.setAttribute("tag", "login");
                response.sendRedirect(request.getContextPath()+"/home.jsp");
            } catch (Exception e) {
    
    
                e.printStackTrace();
            }
        }else{
    
    
            request.setAttribute("login_error", "用户名或者密码有误");
            request.getRequestDispatcher("/login.jsp").forward(request, response);
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        doGet(request, response);
    }

}

14. 项目成果展示

（1）首页展示

（2）注册页面

注册成功，显示5秒后跳转（个人主页）

点击【这里】跳转到个人主页，并且显示当前的时间

将用户注册信息存储到数据库

（3）登录页面

登录成功

登录成功，数据库登录时间更新

用户名或者密码错误