1.完成用户登录功能。

2.完成注册功能。

3.主体利用Maven导入java中的jar包，使用Servlet实现前后端交互，使用mybatis以及注解，mysql进行数据保存，Tomcat服务器进行开发。

效果图

项目结构

代码

1. mapper(相对应注解)

package com.itheima.mapper;

import com.itheima.pojo.User;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

public interface UserMapper {
    /**
     * 用户登陆根据用户和密码来查询用户对象
     * @param username
     * @param password
     * @return
     */
    @Select("select * from tb_user where username=#{username} and password = #{password}")
    User select(@Param("username") String username, @Param("password")String password);

    /**
     * 根据用户名来查询用户是否存在
     * @param usernmae
     * @return
     */
    @Select("select * from tb_user where username=#{username}")
    User selectByUsername(String usernmae);

    /**
     * 判断完是否存在后不存在再进行注册添加用户
     * @param user
     */
    @Insert("insert into tb_user values(null,#{username},#{password})")
    void add(User user);
}

2. pojo(实体类)

package com.itheima.pojo;

public class User {

    private Integer id;
    private String username;
    private String password;

    public Integer getId() {
        return id;
    }

    public void setId(Integer 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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

3.util(工具类)

package com.itheima.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

/**
 *
 * 工具类避免资源浪费多次加载
 */
public class SqlSessionFactoryUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }
}

4.web（Servlet）

1.loginServlet

package com.itheima.web;

import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import com.itheima.util.SqlSessionFactoryUtils;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;

@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1.接收用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //2. 调用Mybatis完成查询

        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

        //2.2获取SqlSession对象
        SqlSession sqlSession =sqlSessionFactory.openSession();

        //2.3获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        //2.4 调用方法
        User user = userMapper.select(username, password);
        //2.5释放资源
        sqlSession.close();
        // 获取相对应的输出流 并设置content
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        //3.判断user是否为null
        if (user!=null){
            //登陆成功
            writer.write("登陆成功");
        }
        else {
            //登陆失败
            writer.write("登陆失败");
        }
    }

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

2.registerServlet

package com.itheima.web;

import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import com.itheima.util.SqlSessionFactoryUtils;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.InputStream;

@WebServlet("/registerServlet")
public class registerServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.接受用户数据
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 封装用户对象
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);
        // 调用Mapper，根据用户名来查询是否
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

        //2.2获取SqlSession对象
        SqlSession sqlSession =sqlSessionFactory.openSession();

        //2.3获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        //2.4 调用方法
        User u = userMapper.selectByUsername(username);

        if (u == null){
            // 用户名不存在
            userMapper.add(user);
            // 提交事务
            sqlSession.commit();
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("注册成功");
        }
        else{
            // 用户名不存在
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("用户已存在,注册失败");

        }
        // 释放资源
        sqlSession.close();
    }

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

5.html

1.login.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>login</title>
    <link href="css/login.css" rel="stylesheet">
</head>

<body>
<div id="loginDiv">
    <form action="/Tomcat-demo1/loginServlet" method="post" id="form">
        <h1 id="loginMsg">LOGIN IN</h1>
        <p>Username:<input id="username" name="username" type="text"></p>

        <p>Password:<input id="password" name="password" type="password"></p>

        <div id="subDiv">
            <input type="submit" class="button" value="login up">
            <input type="reset" class="button" value="reset">
            <a href="register.html">没有账号？点击注册</a>
        </div>
    </form>
</div>

</body>
</html>

2.register.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>欢迎注册</title>
    <link href="css/register.css" rel="stylesheet">
</head>
<body>

<div class="form-div">
    <div class="reg-content">
        <h1>欢迎注册</h1>
        <span>已有帐号？</span> <a href="login.html">登录</a>
    </div>
    <form id="reg-form" action="/Tomcat-demo1/registerServlet" method="post">

        <table>

            <tr>
                <td>用户名</td>
                <td class="inputs">
                    <input name="username" type="text" id="username">
                    <br>
                    <span id="username_err" class="err_msg" style="display: none">用户名不太受欢迎</span>
                </td>

            </tr>

            <tr>
                <td>密码</td>
                <td class="inputs">
                    <input name="password" type="password" id="password">
                    <br>
                    <span id="password_err" class="err_msg" style="display: none">密码格式有误</span>
                </td>
            </tr>

        </table>

        <div class="buttons">
            <input value="注 册" type="submit" id="reg_btn">
        </div>
        <br class="clear">
    </form>

</div>
</body>
</html>

总结

此登陆注册界面使用Maven，Servlet，Mybatis，Mysql，Tomcat技术以及结合了html，css界面设置实现了前后端交互，将前端界面输入的数据传入到后端java中进行处理并将数据保存在mysql数据库之中，是个很不错的练手小项目，新入门小伙伴可以一起尝试。

基本代码如上所示，以上均为手敲，如需所有代码请私信我，谢谢！！！