Re: [Springframework-developer] Passivating statefull session beans

[Colin S. <col...@ex...>]

Tim McAuley wrote:

> Colin Sampaleanu wrote:
>
>> I've modified the EJB support code to allow a user subclass of 
>> AbstractStatelessSessionBean to call a new method unloadBeanFactory() 
>> from ejbPassivate (which it should implement itself). The subclass 
>> should call the existing loadBeanFactory()  from ejbCreate() and 
>> ejbActivate().   As well, the default implementation of ejbRemove 
>> which is in AbstractEnterpriseBean now calls the new 
>> unloadBeanFactory() method.     There is one change that may affect 
>> some existing code, and that is that in the process of adding the 
>> above, I modified the existing BeanFactoryLoader interface to handle 
>> unloading as well as loading of a beanfactory.
>>
>> These changes should allow you to use a Stateful Session bean 
>> properly even  wtih passivation and activation happening.
>>
>> Regards,
>> Colin
>
>
> Colin and others,
>
> We've come across another issue to do with the passivation of beans. 
> While our stateful session bean holds an instance of the bean factory 
> itself (and can control re-initialising it), it is very possible that 
> other standalone beans have a copy of the bean factory as well. If the 
> stateful session bean has references to these other beans then it 
> becomes very difficult to handle.
>
> Is there any reason that the BeanFactory (and Loader) is not 
> serializable. It would make it much easier to handle if they were.
>
> Example of problem:
>
> StatefulSessionBeanA HAS BusinessBeanB HAS BusinessBeanC HAD DAOBeanD
>
> + The Stateful Session bean will load the BeanFactory and lookup 
> BusinessBeanB.
> + BusinessBeanB has the BeanFactory initialised through the 
> ApplicationContext.xml file.
> + BusinessBeanB looks up BusinessBeanC using the BeanFactory.
> + BusinessBeanC initialising DAOBeanD through the 
> ApplicationContext.xml file.
>
> In this case, the stateful session bean has problems serializing 
> BusinessBeanB due to the BeanFactory (XMLBeanFactory in this case).
>
> Any thoughts?
>
> Many thanks!
>
> Tim
>
> PS did you mean AbstractStatelessSessionBean or 
> AbstractStatefulSessionBean above? Stateless beans are not 
> passivated/activated.
>
Of course I meant AbstractStatefulSessionBean, not Stateless...

W/regards to making BeanFactory serializable, Rod and Juergen would 
probably be able to best answer as to why it's not. I can't see much of 
a reason, to tell you the truth, so it's probably just historical. 
ApplicationContext (or most of its implementations rather) can not be 
serializable due to all the non-serializable classes used. So whether 
making BeanFactory serializable is useful to you depends on where you 
are actually using just a BeanFactory, with basic serializable beans in 
it, or are in fact using an ApplicationContext, with AOP, and things 
like interceptors and transaction managers inside it.

Regards,
Colin