getting old values of updated domain properties in grails - events

Question

I am trying to implement the beforUpdate event in grails domain classes I need to audit log both the old and new values of the Domains attributes. I see that we can use the isDirty check or use Domain.dirtyPropertyNames which return list of properties which are dirty in the domain. and getPersistentValue gets the old value in the table so I can have both values..
For implementing this I will be using the beforUpdate event in the domain class and call a logging service from there, passing it the id of the User domain. now using this ID I can get user Instance in Service and then check if any fields are dirty using the above specified method? or do I need to log the Audit when I am actually doing the Update in the UserController's update def?
Which is the better approach?
I want to confirm if this the right approach..
Also what other things I need to take care for, Like:
1) if the attributes are domain object references and not simple types.
2) any other things I need to take care like not flushing out the hibernate session, thinking of implementing this in call to service from the domain class.
Regards,
Priyank
Edit: I tried this in the beforeUpdate event in User domain that I want to Audit log for Update activity..
def beforeUpdate = {
GraauditService service = AH.getApplication().getMainContext().getBean(''graauditService)
service.saveUserUpdateEntry(this.id); // id property of User domain...
}
In the method in Service I do:
def saveUserUpdateEntry(Long id){
User grauser = User.get(id);
println ("user="+ grauser)
println "Dirty Properties -: ${grauser.dirtyPropertyNames}"
println "Changed value for firstName = -: ${ grauser.firstName}"
println "Database value for firstName = -: ${ grauser.getPersistentValue('firstName')}"
}
I try to do the update from the UI for email, firstname, lastname and get the following on console:
user=com.gra.register.User : 1
Dirty Properties -: [eMail, firstName, lastName]
Changed value for firstName = -: sefser
Database value for firstName = -: administer
user=com.gra.register.User : 1
Dirty Properties -: []
Changed value for firstName = -: sefser
Database value for firstName = -: sefser
possible nonthreadsafe access to session
I am not able to know:
1) Why am I getting 2 sets ... is the event called twice once before commit and once after commit...??
2) how to remove or handle the Hibernate exception (tried to use withNew session in the function but no difference
Thanks in Advance..

Answer 1

Rather than using GORM event handlers for audit logging, use audit logging plugin. This will take away a lot of pain of yours.
Hope this helps.
or
If You want much finer control over what you are doing you should consider using a subclass of Hibernate's EmptyInterceptor. This will serve tow purposes for you
Will give you much finer control over what and how you are doing the audit logging
Will place all your logic for audit logging at one place, which will help you maintaining your code.
Click here to see the API for EmptyInterceptor.
Note: Hibernate does not ship any implementation in this class and also don't provide any subclass of this which might provide you the default behavior. So you will have to write a custom implementation.