Hibernate - unique column constraint being ignored

Question

I have a MySQL table to hold tags (i.e. like those used here on Stack Overflow). It simply has an id (pk) and a tag column to hold the tag itself.

The annotated get

Answer 1

From JavaDoc of UniqueConstraint (unique=true on @Colunm is just a shortcut):

This annotation is used to specify that a unique constraint is to be included in the generated DDL for a primary or secondary table.

So it does not seem to enforce uniqueness upon inserts. You should create a unique constraint in the database in any case.

Answer 2

You miss that this is only a information.

You should add also constraint on the column in database.