package org.rain.mybatis.utils;

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

/**
 * @author liaojy
 * @date 2023/5/19 - 7:41
 */
public class SqlSessionUtils {
    public static SqlSession getSqlSession(){
        SqlSession sqlSession = null;

        try {
            //读取MyBatis核心配置文件的输入流
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            //创建SqlSessionFactoryBuilder对象
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            //通过核心配置文件所对应的字节输入流创建工厂类SqlSessionFactory，用于生产SqlSession对象
            SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
            //创建自动提交事务的SqlSession对象
            sqlSession = sqlSessionFactory.openSession(true);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sqlSession;
    }
}

3.2.1、接口方法

void updateUser();

3.2.2、映射文件

    <!--void updateUser();-->
    <update id="updateUser">
        update t_user set username='root',password='123' where id = 3
    </update>

3.2.3、测试方法

    @Test
    public void testUpdate(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.updateUser();
        sqlSession.close();
    }

3.2.4、执行效果

-----------------------------------分割线-----------------------------------

3.3.1、接口方法

void deleteUser();

3.3.2、映射文件

    <!--void deleteUser();-->
    <delete id="deleteUser">
        delete from t_user where id = 2
    </delete>

3.3.3、测试方法

    @Test
    public void testDelete(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.deleteUser();
        sqlSession.close();
    }

3.3.4、执行效果

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3.4.1、接口方法

User getUserById();

3.4.2、映射文件

注意：

查询的标签select必须设置属性resultType或resultMap，用于设置实体类和数据库表的映射关系

resultType：自动映射，设置查询结果要转换为的Java类型，用于属性名和字段名一致的情况

resultMap：自定义映射，用于一对多或多对一，或用于字段名和属性名不一致的情况

    <!--User getUserById();-->
    <select id="getUserById" resultType="org.rain.mybatis.pojo.User">
        select * from t_user where id = 3
    </select>

3.4.3、测试方法

    @Test
    public void testGetUserById(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.getUserById();
        System.out.println(user);
        sqlSession.close();
    }

3.4.4、执行效果

3.5.1、接口方法

List<User> getAllUser();

3.5.2、映射文件

    <!--List<User> getAllUser();-->
    <select id="getAllUser" resultType="org.rain.mybatis.pojo.User">
        select * from t_user
    </select>

3.5.3、测试方法

    @Test
    public void testGetAllUser(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> allUser = userMapper.getAllUser();
        for (User user : allUser) {
            System.out.println(user);
        }
        sqlSession.close();
    }

3.5.4、执行效果