Attaches a detached domain instance to the Hibernate session bound to the current thread


def b = Book.get(1)
b.title = "Blah"


if(!b.isAttached()) { b.attach() }


Grails uses Hibernate which manages each persistent object in a persistence session. A new session is created per request and is closed at the end of the request. If an object is read from the session and placed into a web scope such as the HttpSession it is seen as detached, since the persistence session has been closed. You can use the attach() method to re-attach an existing persistent instance to the persistence session of the current request.