案例-用户注册-526互联

package com.itheima.web;

import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
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.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
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);

        //2.调用mapper 根据用户名调查用户对象
        //2.1 获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //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);

        //3.判断用户对象是否为null
        if (u == null){
            //用户名不存在，可以添加用户
            UserMapper.add(user);
            //设置 防止乱码
            response.setContentType("text/html;charset=utf-8");
            //调用Writer输出
            response.getWriter().write("注册成功");
            //提交事务
            sqlSession.commit();
            //释放资源
            sqlSession.close();
        }else {
            //用户名存在，给出提示信息
            //设置 防止乱码
            response.setContentType("text/html;charset=utf-8");
            //调用Writer输出
            response.getWriter().write("用户名已存在");
        }

    }

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

}

<!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="/RootDemo1/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>

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 {
    /*
    * 根据用户名和密码查询用户对象
    * */
    @Select("select * from tb_user where username = #{username} and password =#{password}")
    User select(@Param("username") String username,@Param("password") String password);

    /*
    * 根据用户名查询用户对象
    * */
    @Select("select * from tb_user where username=#{username}")
    User selectByUsername(String username);

    /*
    * 添加用户
    * */
    @Insert("insert into tb_user values (null,#{username},#{password})")
    void add(User user);
}

用户注册