FactoryBean 的处理代码：

    FactoryBean 接口可以让大家自主创建bean，创建的bean会纳入Spring IOC管理。其使用例子如下：

    2：FactoryBean的实现类：MyTestFactoryBean 初始化后，会保存到 singletonObjects 缓存里面，通过bean名称从singletonObjects 获取到的实例是FactoryBean实例。

    3：然后Spring发现如果bean是实现了 FactoryBean 接口。则会调用FactoryBeanRegistrySupport#getObjectFromFactoryBean 处理的。在这个方法里，如果 isSingleton 方法返回为true，则会添加到缓存 factoryBeanObjectCache 中。而且最终获取到的对象是 FactoryBean 接口的 getObject 方法中获取的。代码如下：
```
protected ObjectgetObjectForBeanInstance(

Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {
    // Don't let calling code try to dereference the factory if the bean isn't a factory.
    if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstanceinstanceof FactoryBean)) {
        throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
     }

    // Now we have the bean instance, which may be a normal bean or a FactoryBean.
    // If it's a FactoryBean, we use it to create a bean instance, unless the
    // caller actually wants a reference to the factory.
    if (!(beanInstanceinstanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
        return beanInstance;
       }

    Object object =null;
   if (mbd ==null) {
        object = getCachedObjectForFactoryBean(beanName);
       }

    if (object ==null) {
    // Return bean instance from factory.
      FactoryBean factory = (FactoryBean) beanInstance;
      // Caches object obtained from FactoryBean if it is a singleton.
      if (mbd ==null && containsBeanDefinition(beanName)) {
        mbd = getMergedLocalBeanDefinition(beanName);
      }

        boolean synthetic = (mbd !=null && mbd.isSynthetic());
      object = getObjectFromFactoryBean(factory, beanName, !synthetic);
   }
return object;
}
```