On this blog post Jochen Theodorou uses Groovy features like operator overloading and closures to write SODA queries like the following:
Query query=db.query();
query.constrain(Pilot.class);
query.name == "Michael Schumacher" && query.points == 99
Query query=db.query()
query.constrain(Pilot.class)
query.constrain { it.name.length() < 5 }
Very nice syntactic sugar, very sweet!
I would love to have Groovy functionality available for the work on the db4o core itself but unfortunately we must stay compatible to JDK 1.1.