Check constraint metadata

Hi all

I've written an ant task which reverse engineers a postgresql database 
into JPA Annotated Entity classes for Hibernate/TopLink etc. So far so good.

For my next trick I want to reverse engineer null/not null and check 
constraints into Spring Validator classes so I can do validation in the 
web tier (and potentially as downloaded JavaScript in the browser). The 
reason I want to have validation based on check constraints is that the 
database will potentially be updated from other legacy applications.

I can't see any custom extensions to extract check constraints - are 
there any?

If I'm barking up the wrong tree, or if there is a better approach 
please feel free.

many thankis
Roy