grails - Converting Mutable to Immutable with Hibernate -

i'm using grails , have following domain class:

class pack {   string code    date publisheddate   //several other properties (including collections hasmany)....    def ispublished() {     return publisheddate != null   }    def publish() {     publisheddate = new date()       }    def canedit() {     return !ispublished()   } } 

to sell pack first need publish , use publish method publicate pack.

after published, pack cannot changed (i.e. after published, pack need immutable instance).

my question is:

• how transform mutable object in immutable using groovy?

or

• is there way retrieve immutable instance hibernate?

another option use canedit() method combined hibernate events (beforeupdate , beforedelete). if canedit() == false can throw runtimeexception inside beforedelete or beforeupdate. solution?

obs.: think freeze method in ruby need. (http://rubylearning.com/satishtalim/mutable_and_immutable_objects.html)

you can use pack.read( id )

an instance of domain class specified id in read-only state. null returned if row specified id doesn't exist.

see http://grails.org/doc/latest/ref/domain%20classes/read.html