Check if @ManyToOne and @OneToOne associations are unproxied when using bytecode enhancement lazy loading

[vladmihalcea]

As explained by @pblanchardie in this Jira issue. when using bytecode enhancement lazy loading, all @ManyToOne and @OneToOne associations should be unproxied in the following ways:

1. By setting hibernate.bytecode.allow_enhancement
2. By annotating the associations with @LazyToOne(LazyToOneOption.NO_PROXY)

Otherwise, the associations are fetched eagerly by some recent Hibernate issues.

[pblanchardie]

Note that hibernate.bytecode.allow_enhancement is also causing some weird issues and should be avoided until stable IMO.
It looks like it's still a tech preview in best effort mode, as explained by Steve Ebersole.
eg.:
HHH-14360 (fixed)
HHH-14395
HHH-14396
I'm currently reverting the use of lazy initialization with bytecode enhancement, as it brought more trouble than advantages. Better stick with specific mappings, sub-entities, projections, good old stored functions and views or jOOQ when applicable!

[pblanchardie]

Good news from Hibernate:
HHH-13658 - Make NO_PROXY unnecessary was planned for 6.0 and should be applied to 5.4 soon.

There is one left, but it should also be fixed:
HHH-13134 - JOIN FETCH does not work properly with enhanced entities

Looking forward to using bytecode enhancement with lazy initialization without troubles!

[pblanchardie]

Hi @vladmihalcea,
These issues have been fixed so we should not get OneToOneParentSideEvent anymore when using Hibernate 5.5+.
Related to #120
See https://patriceblanchardie.com/hibernate-lazy-initialization

[vladmihalcea]

Thanks for the tip. I'll have to test it with the latest 5.5 branch and see what's the best fix for it.

[vladmihalcea]

@pblanchardie I created #160 and I'll leave this issue open to see whether for 5.3 and 5.4 we need to provide the user with the hint about hibernate.bytecode.allow_enhancement.

[vladmihalcea]

@pblanchardie Check out the 2.5.1 release, as it fixes the OneToOneParentSideEvent issue being triggered if you don't have LazyToOneOption.NO_PROXY annotation.