mybatis--MapperScannerConfigurer

时间:2024-04-05 13:37:04

一般我们这样配置

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"
lazy-init="false">
<property name="dataSource" ref="dataSource"/>
<property name="mapperLocations" value="classpath:sqlmapper/*Mapper.xml"/>
<property name="plugins">
<list>
<bean class="***">
<property name="dialect">
<bean class="***"/>
</property>
</bean>
</list>
</property>
</bean>
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="*.*.*" />
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
</bean>

内部使用 ClassPathMapperScanner 来扫描包下面的mapper接口,每个接口构建一个BeanDefinitionHolder(beanclass为MapperFactoryBean)

当需要mapperinterface实例时,由MapperFactoryBean工厂产生

public T getObject() throws Exception {
return this.getSqlSession().getMapper(this.mapperInterface);
}

可以吧this.getSqlSession()看做是sqlSessionFactory的封装SqlSessionTemplate,实际调用

public <T> T getMapper(Class<T> type) {
return this.getConfiguration().getMapper(type, this);
}

这里的this.getConfiguration()实际是

return this.sqlSessionFactory.getConfiguration();

走到这步,就必须来看SqlSessionFactoryBean做了什么吧?关键方法如下:

protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
XMLConfigBuilder xmlConfigBuilder = null;
Configuration configuration;
..................
if(this.transactionFactory == null) {
this.transactionFactory = new SpringManagedTransactionFactory();
} Environment var29 = new Environment(this.environment, this.transactionFactory, this.dataSource);
configuration.setEnvironment(var29);
   ............... if(!ObjectUtils.isEmpty(this.mapperLocations)) {
XMLMapperBuilder e = new XMLMapperBuilder(var33.getInputStream(), configuration, var33.toString(), configuration.getSqlFragments());
e.parse();
}
return this.sqlSessionFactoryBuilder.build(configuration);
}

红色部分,设置configuration->environment->springManagedTransactionFactory

XMLMapperBuilder 详细过程见 mybatis缓存创建过程 ,parse中xml的namespace相应的class注册给configuration

public <T> void addMapper(Class<T> type) {
this.mapperRegistry.addMapper(type);
}

最后的return调用 SqlSessionFactoryBuilder

public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}

这里的Configuration对象很关键

总结如下:org.mybatis.spring.SqlSessionFactoryBean解析mapper xml配置,根据namespace添加class mapper组装Configuration对象,包装为DefaultSqlSessionFactory;

org.mybatis.spring.mapper.MapperScannerConfigurer扫描basePackage下的mapper接口,封装为MapperFactoryBean注册给spring容器,当调用"mapper接口"时去DefaultSqlSessionFactory-》Configuration获得接口类的代理类

MapperProxy mapperProxy = new MapperProxy(sqlSession, this.mapperInterface, this.methodCache);

进一步的调用过程见 mybatis缓存

如何在调用中事务起作用,见下篇