+ def not_null_constraints(self):
+ '''
+ Returns a list of properties that must be not NULL. Derived classes
+ should override this method if needed.
+ '''
+ return []
+
+ validation_message = \
+ "Validation failed because property '%s' must not be empty in object\n%s"
+
+ def validate(self):
+ '''
+ This function validates the not NULL constraints as returned by
+ not_null_constraints(). It raises the DBUpdateError exception if
+ validation fails.
+ '''
+ for property in self.not_null_constraints():
+ # TODO: It is a bit awkward that the mapper configuration allow
+ # directly setting the numeric _id columns. We should get rid of it
+ # in the long run.
+ if hasattr(self, property + '_id') and \
+ getattr(self, property + '_id') is not None:
+ continue
+ if not hasattr(self, property) or getattr(self, property) is None:
+ raise DBUpdateError(self.validation_message % \
+ (property, str(self)))
+