Hibernate very nicely handles relationships between objects and does the correct lazy loading against the DB.

Is there a place where I can plug into this my own lazy-loading proxy implementation? A class that takes the parameters from the parent record and does something a little different when fetching the child records? I need (ideally) to substitute just a tiny bit of the SQL.

There are several places to look:

(1) use a custom persister
(2) implement ProxyFactory (requires 2.1.2)
(3) implement Type (look at ManyToOneType)

How do I tell Hibernate to use a different one?

1.: <class persister="...">
2.: Extend AbstractEntityPersister and override createProxyFactory()
3.: <property type="...">