Mybatis整合Spring原始碼之前也分析過一次了，這次剛好腦袋靈光一閃，想出來一個在

　 SqlSessionDaoSupport.setSqlSessionFactory 是什麼時候呼叫的呢？

一 BeanDefinition

　　每一個mapper介面都會被掃描成一個BeanDefinition，這個BD開始會被強制轉成MapperFactoryBean型別，並

　　ClassPathMapperScanner.processBeanDefinitions

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
    GenericBeanDefinition definition;
    
 
for (BeanDefinitionHolder holder : beanDefinitions) {
      definition = (GenericBeanDefinition) holder.getBeanDefinition();

      if (logger.isDebugEnabled()) {
        logger.debug("Creating MapperFactoryBean with name '" + holder.getBeanName() 
          + "' and '" + definition.getBeanClassName() + "' mapperInterface");
      }

      
 
// the mapper interface is the original class of the bean
      // but, the actual class of the bean is MapperFactoryBean
      definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59
      definition.setBeanClass(this.mapperFactoryBean.getClass());

      definition.getPropertyValues().add(
 
"addToConfig", this.addToConfig);

      boolean explicitFactoryUsed = false;
      if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
        definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
        explicitFactoryUsed = true;

在這個BD中，mapper的原始類加入到構造方法入參，sqlSessioinFactory放進了bd的屬性裡

二 生效時機

　　通過構造方法，Class<T> mapperInterface被注入了

public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {

  private Class<T> mapperInterface;

  private boolean addToConfig = true;

  public MapperFactoryBean() {
    //intentionally empty 
  }
  
  public MapperFactoryBean(Class<T> mapperInterface) {
    this.mapperInterface = mapperInterface;
  }

sqlSessioinFactory的注入在對bean的初始化的第二步

protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
        PropertyValues pvs = mbd.getPropertyValues();

        if (hasInstAwareBpps || needsDepCheck) {//這部分是對@AutoWired或者@Resource進行注入的
            PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
            if (hasInstAwareBpps) {
                for (BeanPostProcessor bp : getBeanPostProcessors()) {
                    if (bp instanceof InstantiationAwareBeanPostProcessor) {
                        InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
                        pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
                        if (pvs == null) {
                            return;
                        }
                    }
                }
            }
            if (needsDepCheck) {
                checkDependencies(beanName, mbd, filteredPds, pvs);
            }
        }
　　　　　//走完了上面的程式碼後這個bean的@AutoWired或者@Resource的屬性就已經注入完了

　　　　 applyPropertyValues(beanName, mbd, bw, pvs); //這個方法處理的是BeanDefinition裡的靜態屬性，也就是BeanDefinition裡已經寫好了的屬性
}

applyPropertyValues會對BD中的全部屬性進行處理，我看了下呼叫還有點複雜，不過底層應該還是通過Field的反射介面

這樣，我們就知道了sqlSessioinFactory是怎麼注入的了