十四、MyBatis入门

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官网：https://mybatis.org/mybatis-3/zh/index.html

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1、MyBatis开发流程六步骤

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2、MyBatis使用细则

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MybatisUtils.java工具类：

/**
 * MybatisUtils工具类，创建全局唯一的SqlSessionFactory对象
 */
public class MybatisUtils {
    //利用static（静态）属于类不属于对象，且全局唯一
    private static SqlSessionFactory sqlSessionFactory = null;
    //利用静态块在初始化类是实例化sqlSessionFactory
    static {
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            e.printStackTrace();
            //初始化错误时，通过抛出异常ExceptionInInitializerError通知调用者
            throw new ExceptionInInitializerError(e);
        }
    }

    /**
     * openSession创建一个新的SqlSession对象
     * @return SqlSession对象
     */
    public static SqlSession openSession() {
        return sqlSessionFactory.openSession();
    }

    /**
     * 释放一个有效的SqlSession对象
     * @param session 准备释放SqlSession对象
     */
    public static void closeSession(SqlSession session) {
        if (session != null) {
            session.close();
        }
    }
}

mybatis-config.xml配置文件：

goods.xml创建Mapper XML

    
        select * from t_goods order by goods_id desc limit 10
    


    
        select * from t_goods where goods_id = #{value}
    


    
        select * from t_goods
        where
            current_price between #{min} and #{max}
        order by current_price
        limit 0,#{limit}
    


    
        select g.*,c.category_name from t_goods g join t_category c on g.category_id = c.category_id
    


    

        

        
        
        
        
        
        
        
        
    
    
        select g.*,c.category_name,'1' as test from t_goods g join t_category c on g.category_id = c.category_id
    

    
        insert into t_goods (title,sub_title,original_cost,current_price,discount,is_free_delivery,category_id) values
        (#{title},#{subTitle},#{originalCost},#{currentPrice},#{discount},#{isFreeDelivery},#{categoryId})





    

    
        update t_goods
        set title     = #{title},
            sub_title = #{subTitle},
            original_cost = #{originalCost},
            current_price = #{currentPrice},
            discount = #{discount},
            is_free_delivery = #{isFreeDelivery},
            category_id = #{categoryId}
        where goods_id = #{goodsId}
    

    
        delete from t_goods where goods_id = #{value}
    

MyBatisTestor.java测试类：

public class MyBatisTestor {

    @Test
    public void testSqlSessionFactory() throws IOException {
        //利用Reader加载classpath下的mybatis-config.xml核心配置文件
        Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
        //初始化SqlSessionFactory对象，同时解析mybatis-config.xml文件
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        System.out.println("sqlSessionFactory加载成功");
        SqlSession sqlSession = null;

        try {
            //创建SqlSession对象，SqlSession是JDBC的扩展类，用于与数据库交互
            sqlSession = sqlSessionFactory.openSession();
            //创建数据库连接（测试用）
            Connection conn = sqlSession.getConnection();
            System.out.println(conn);
        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (sqlSession != null) {
                //如果type="POOLED",代表使用连接池，close则是将连接回收到连接池中
                //如果type="UNPOOLED",代表直连，close则会调用Connection.close关闭连接
                sqlSession.close();
            }
        }
    }

    @Test
    public void testMyBatisUtils() throws Exception {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();
            Connection connection = sqlSession.getConnection();
            System.out.println(connection);
        } catch (Exception e) {
            throw e;
        } finally {
            MybatisUtils.closeSession(sqlSession);
        }
    }

    @Test
    public void testSelectAll() throws Exception {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();
            List list = sqlSession.selectList("goods.selectAll");
            for (Goods g : list) {
                System.out.println(g.getTitle() + g.getSubTitle());
            }
        } catch (Exception e) {
            throw e;
        } finally {
            MybatisUtils.closeSession(sqlSession);
        }
    }

    @Test
    public void testselectById() throws Exception {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();
            Goods g = sqlSession.selectOne("goods.selectById",1903);
            if (g != null) {
                System.out.println(g.getTitle() + g.getSubTitle());
            }else {
                System.out.println("未找到您查找的数据");
            }
        } catch (Exception e) {
            throw e;
        } finally {
            MybatisUtils.closeSession(sqlSession);
        }
    }

    @Test
    public void testSelectByPriceRange() throws Exception {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();
            Map param = new HashMap<>();
            param.put("min",100);
            param.put("max", 500);
            param.put("limit", 1);
            List list = sqlSession.selectList("goods.selectByPriceRange", param);

            for (Goods g : list) {
                System.out.println(g.getTitle() + g.getSubTitle());
            }
        } catch (Exception e) {
            throw e;
        } finally {
            MybatisUtils.closeSession(sqlSession);
        }
    }

    @Test
    public void testSelectGoodsMap() throws Exception {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();

            List