[Springframework-developer] JPA support using JpaDaoSupport

[Thomas R. <tho...@tr...>]

I've been examining the JPA support in 2.0 and i have a few issues  
around the JpaDaoSupport class.  There are two ways of configuring  
this class - either you provide an EntityManager or an  
EntityManagerFactory.  Which one you provide dictates what  
JpaDaoSupport methods you can effectively use later on in your code.  
This, I think, couples your code to configuration choices.  If you  
provide an EntityManagerFactory then the getEntityManager method  
returns null and you are forced to use getEntityManagerFactory  
method.  If you provide an EntityManager, then it's the other way  
around, you must use the getEntityManager method since  
getEntityManagerFactory returns null.

This EntityManagerFactory/EntityManager issue provides a non- 
intuitive split in the API usage and will confuse the heck out of  
everyone.  We need to come up with some strategy to make it easier to  
directly use an EntityManager instance for both configuring this  
class and for gaining access to an instance of EntityManager that  
will participate in Spring managed transactions regardless of how the  
JpaDaoSupport was configured.

I would prefer to have a solution where we can do the right thing  
behind thes scenes instead of simply returning a null.  We should  
either return a "managed" object of the type requested or throw and  
InvalidApiUsage type exception.

Thomas