一般我们这样配置

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 getMapper(Class
     
       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  ，parse中xml的namespace相应的class注册给configuration

public 
    
      void addMapper(Class
     
       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 

 

如何在调用中事务起作用，见下篇