Mybatis-lesson2-2023-3-10

查，增，改，删

第一步：接口写入新方法

package com.feijian.dao;

import com.feijian.pojo.User;

import java.util.List;

public interface UserMapper {
    //1.查询全部用户
    List <User> getUserList();

    //2.根据ID查询用户
    User getUserById(int id);

    //3.增加一个用户
    int addUser(User user);

    //4.修改用户
    int updateUser(User user);

    //5.删除用户
    int deleteUser(int id);
}

第二步：UserMapper.xml文件中写入对应代码 select update insert delete

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.feijian.dao.UserMapper">
    
    <!--查询全部用户-->
    <select id="getUserList" resultType="com.feijian.pojo.User">
        select * from mybatis.user
    </select>
    
    <select id="getUserById" parameterType="int" resultType="com.feijian.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>

    <insert id="addUser" parameterType="com.feijian.pojo.User">
        insert into mybatis.user(id,name,pwd) values (#{id},#{name},#{pwd});
    </insert>

    <update id="updateUser" parameterType="com.feijian.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd}  where id =#{id}
    </update>

    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id =#{id}
    </delete>
</mapper>

 第三步：测试类测试 注意增，删，改要提交事务

package com.feijian.dao;
import com.feijian.pojo.User;
import com.feijian.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {
    //查询全部用户
    @Test
    public void test(){
        //第一步获得sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        try{
            //方式一：执行SQL
            UserMapper userDao = sqlSession.getMapper(UserMapper.class);
            List<User> userList = userDao.getUserList();

            for (User user : userList) {
                System.out.println(user);
            }
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            //关闭sqlSession
            sqlSession.close();
        }
    }
   //查询某个用户
    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = mapper.getUserById(1);
        System.out.println(user);

        sqlSession.close();

    }

    //增加用户 增删改要提交事务
    @Test
    public void AddUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.addUser(new User(8, "rui", "56789"));
        if (res>0){
            System.out.println("插入成功！！！");
        }
        //提交事务
        sqlSession.commit();
        //关闭
        sqlSession.close();
    }
    //修改用户
@Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        mapper.updateUser(new User(8,"更改","666666"));

        sqlSession.commit();
        sqlSession.close();
    }
    //删除用户
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        mapper.deleteUser(8);
        sqlSession.commit();
        sqlSession.close();

    }

}