mybatis源码学习笔记-蒲公英云

mybatis源码学习笔记

1.读取配置文件mybatis-config.xml

<?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>
    <!--数据库配置文件-->
    <properties resource="jdbc.properties"></properties>
    <typeAliases>
        <package  name="com.xqc.model" />
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driverClass}" />
                <property name="url" value="${jdbc.url}" />
                <property name="username" value="${jdbc.username}" />
                <property name="password" value="${jdbc.password}" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/EoStockMapper.xml" />
    </mappers>
</configuration>

注意配置文件的属性顺序，不然会报错，typeAliases要写在properties猴儿面，不然会报错，例如这样写

读取mybatis-config.xml的方法

InputStream is = Resources.getResourceAsStream("mybatis-config.xml");

2.创建SqlSessionFactory，最为关键的步骤

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

SqlSessionFactory的解析过程，解析configuration的属性，
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mybatis解析mappers文件的几种方式，官网上有4种，resource、url、class、package

其中package优先级最高。接着是resource、url、class

3.打开SqlSession

SqlSession sqlSession = sqlSessionFactory.openSession();

mybatis的三种执行器，默认是SIMPLE

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mybatis的一级缓存默认是开启的

4.执行SQL

EoStockMapper eoStockMapper = sqlSession.getMapper(EoStockMapper.class);
EoStockMapper接口文件
public interface EoStockMapper {
    List<EoStockModel> selectList();
}
EoStockMapper接口对应的xml文件
<?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.xqc.mapper.EoStockMapper" >
    <select id="selectList" resultType="EoStockModel"  useCache="false" flushCache="true">
        select
        *
        from eo_stock
    </select>
</mapper>
为什么只写接口和xml就能实现查询返回结果呢？核心精髓就是jdk的动态代理

连续查询两次，第二次没有查询数据库，（同一个SqlSession ，不同的SqlSession对象都是相互隔离的）
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关闭一级缓存的方法：sql映射文件的配置

可以看到两次都查询了数据库