mybatis案例--mapper代理开发

mybatis案例之mapper代理开发

在使用mybatis的代理开发的时候，需要遵循的要求如下

• 定义接口，要求接口名和映射配置文件名一致
• 接口必须和映射配置文件在同一级包中
• 映射配置文件的namespace需要和接口的全类名一致
• 映射配置文件的sql语句要和接口中的抽象方法保持一致
  • id的值和接口的抽象方法名一致
  • resultType和抽象方法返回值保持一致

第一步，编写mybatis核心配置文件

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    settings>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///db1?useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            dataSource>
        environment>

    environments>
    <mappers>
        
        
        
        <package name="com.itheima.mapper"/>

    mappers>


configuration>

第二步：编写BrandMapper接口

package com.itheima.mapper;

import com.itheima.pojo.Brand;

import java.util.List;

public interface BrandMapper {

    /**
     * 查询所有
     * @return
     */
    List<Brand> selectAll();
}

第三步，编写BrandMapper映射文件

• namespace中要填写接口的全路径名

• resultType中写上selectAll方法的返回值类型，应该和接口中的方法返回值一致

• id的值要和接口中的方法名一致

<?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">

<mapper namespace="com.itheima.mapper.BrandMapper">

    <!-- 跟user表相关的sql语句-->
    <select id="selectAll" resultType="com.itheima.pojo.Brand">
        select *
        from tb_brand
    </select>


</mapper>

第四步，编写测试类进行测试

package com.itheima;

import com.itheima.mapper.BrandMapper;
import com.itheima.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 test {

    @Test
    public void test01() throws IOException {

        //读取核心配置文件
        InputStream in = Resources.getResourceAsStream("mybatis.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);

        //去获取连接  得到sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //获取mapper对象
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);

        //执行语句
        List<Brand> brands = brandMapper.selectAll();

        for (Brand brand : brands) {
            System.out.println(brand);
        }

        //释放资源
        sqlSession.close();


    }
}

运行结果测试: