每日记录（十一）2023.03.03

今天，学习了mybatis的基本东西

esource/mybatis-config.xml

写SQL语句

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <typeAliases>
        <package name="com.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;allowPublicKeyRetrieval=true&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="wmx021207"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--扫描mapper-->
        <package name="com.mapper"/>
    </mappers>
</configuration>

MybatisDemo

String resource = "mybatis-config.xml";

        InputStream inputStream = Resources.getResourceAsStream(resource);

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);











//2、获取sql.....对象，用来执行sql

        SqlSession sqlSession = sqlSessionFactory.openSession();





//执行sql语句

        List<User> users = sqlSession.selectList("test.selectAll");



        System.out.println(users);

#

BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

List<Brand> brands = mapper.selectAll();



for(Brand u:brands)

{

    System.out.println(u);

}

#



//4、释放资源



        sqlSession.close();

……Mapper.xml

pper namespace="com.mapper.BrandMapper">



<!--数据库表的字段名称和实体类的不一样，则不能自动封装数据

*起别名：对不一样的列名起别名，让别名和实体类的属性名一样

*缺点：每次查询都要定义一次别名

*resultMap

-->



    <resultMap id="brandResultMap" type="brand">

        <result column="brand_name" property="brandName"></result>

        <result column="company_name" property="companyName"></result>

    </resultMap>





    <select id="selectAll" resultMap="brandResultMap">

        select * from tb_brand;

    </select>