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

    
    
    


    

        
LOGIN IN
        
Username:
        
Password:
        
            
            
            没有账号？点击注册
        
    

2.register.html

    
    
    


    
        
欢迎注册
        已有帐号？ 登录
    
    

        

            

                
用户名
                

                    
                    

                    用户名不太受欢迎
                
            
            

                
密码
                

                    
                    

                    密码格式有误
                
            
        
        
            
        
        

    

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！！！