[hibernate-dev] Is bytecode enhancement enabled by default in 5.3?

[Scott Marlow]

On 05/23/2018 09:17 AM, Steve Ebersole wrote:
> I never understood this `DataSourceDefinitions` part.  Why can't they 
> just be discovered via jipijapa prior to doing anything with Hibernate/JPA?

The @DataSourceDefinition DataSource that ORM needs, doesn't start until 
after application classes are loaded/defined.

> 
> See inline...
> 
>     Steve Ebersole and I have talked about adding additional phases to the
>     PU bootstrap, but that was so long ago, I forget if it was about
>     registering the ORM class transformer [1] earlier.  If ORM 5.3 or 6.0,
>     is depending on [1] to work correctly in order to implement the ORM
>     features, we need to take some action.
> 
> 
> So the rub right now (up through and including) 5.3 is that we sometimes 
> load domain model Class references during this "first bootstrap phase".  
> What really needs to happen is for Hibernate to unequivocally delay 
> loading domain model Class references until after this phase is over - 
> at least delay loading them into the "real" ClassLoader, we can use the 
> JPA temp ClassLoader if it is available.
> 
> 6.0 will delay loading these Class references even more so than today.  
> However, even with 6.0 we cannot fully guarantee that we will never load 
> them during this 1st phase.  That is a design goal for 7.0 and the move 
> to Jandex.
> 
>     In the past, I recall someone mentioning that lazy loading or dirty
>     flag
>     handling, would depend on bytecode enhancing.  If that happened or will
>     happen, we should discuss what the fallback solution is for when
>     bytecode enhancing is not working.
> 
> 
> Bytecode enhancement is not needed for either of these - Hibernate can 
> (and has forever) supported these without enhancement.  That will 
> continue to be the case.  Bytecode enhancement is simply an alternative 
> means for adding these features.

This is good news, so applications will still work correctly.

> 
> However, certain features such as automatic bi-dir association 
> management does require enhancement to work.

Should we document that applications with entity classes using bi-dir 
association, also depend on enhancement working?  And also mention why 
run-time enhancement might not work and perhaps mention build-time 
enhancement as a workaround to run-time enhancement not working?

> 
>     Another subject, is how should a user find out that bytecode enhancing
>     is actually updating application entity classes.  Should that operation
>     have trace logging and should that be at the WF or ORM level?
> 
> 
> Well based on what you described it sounds to me like there ought to be 
> at least 2 different log events here:
> 
>  1. The transformer is registered (this could be either WF or Hibernate
>     or both)
>  2. The transformer calls the Enhancer

https://issues.jboss.org/browse/WFLY-10456 is for #1 + #2.

>  3. (?) Enhancer enhances a class.  Enhancer is an interface though and
>     this would rely on the impls (Javassist and Byte Buddy) to do this.
> 

+10 for ORM to also log #2 + #3. :)

Scott