javaweb--MyBatis案例-环境准备

安装MybatisX

可以提高效率

sql映射文件BrandMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace：名称空间。写接口给的全类名，相当于告诉MyBatis这个配置文件是实现哪个接口的。-->

<mapper namespace="com.avb.Mapper.BrandMapper">
    <!--resultType=""指定查询数据封装结果的时候使用自定义封装规则-->
    <select id="selectAll" resultType="brand">
        select * from tb_brand;
    </select>
    <!--&lt;!&ndash;type指定为哪个javaBean自定义封装规则，id是唯一标识&ndash;&gt;
    <resultMap id="mycat" type="smq.javabean.Cat">
        &lt;!&ndash;id指定主键列的对应规则，column指定哪一列是主键列，property指定cat的哪个属性封装id这个列数据&ndash;&gt;
        <id column="id" property="id"/>
        &lt;!&ndash;普通列&ndash;&gt;
        <result column="cName" property="name"/>
        <result column="cgender" property="gender"/>
        <result column="cAge" property="age"/>
    </resultMap>-->

</mapper>

接口文件BrandMapper

package com.avb.Mapper;

import com.avb.pojo.Brand;
import com.avb.pojo.User;

import java.util.List;

public interface BrandMapper {
    List<Brand> selectAll();
}

 查询所有

package com.avb.test;

import com.avb.Mapper.BrandMapper;
import com.avb.pojo.Brand;
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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybstisTest {
    @Test
    public void testSelectAll() throws IOException {
        //1、获取sqlSessionFactory
        String rescource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(rescource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2、获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //3、获取Mapper接口的代理对象
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
        //4、执行方法
        List<Brand> brands = brandMapper.selectAll();
        System.out.println(brands);
        //5、释放资源
        sqlSession.close();

    }
}

 如果数据库中字段名称和实体类中的属性名称不相同，则不能自动封装数据

解决：给字段起别名

select company_name as company_Name from tb_brand;