mybatis--MapperScannerConfigurer

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