Grails: Collection in domain object without hasMany

Question

I have two domain objects A and B.

A can be associated with many Bs but I do not want any save cascade from A to B.

I'm thinking of defining the hasMany relationship form A to B, but then setting a cascade behavior. Any ideas?

This is an example of my domain objects:

class A{

static hasMany = [bees:B] }

class B{ }

Answer 1

If you do not wish for GORM to manage the save/updates for your collection simply don't use hasMany. Instead treat it as a simple HashSet property.

Answer 2

Why not use 'belongsTo' on B, and don't declare anything on A? This way you'll get the foreign key to 'A', but operations on 'A' won't affect 'B'. You lose a bit of convenience, but can still easily look up all 'B' by 'A'. I actually prefer this because I don't need to worry about lazy loading gotchas and hibernate going and loading all the 'B's when I'm just trying to add one (assuming you don't need that functionality).

class A{}

class B{
  static belongsTo = [your_a:A]
 }

 //get your B's for a given A
  B.findAllByA(your_A_instance, ...paging, etc...)

Answer 3

You can define your own cascading behavior in the static mappings block of your Domain class.

See here: http://grails.org/doc/latest/ref/Database%20Mapping/cascade.html

Answer 4

If you are saying what I think your are saying then what you are talking about is not cascading. A simple outline of your classes would be helpful. If you have an instance of A which is associated with many instances of B, then all instance of B which reference the instance of A in question are referencing the exact same object. I had the same problem and asked a similar question here. Basically your options are:

1.) Clone the instance of A whenever it changes or whenever you deem appropriate.

2.) Create new fields in your B class which will hold the values of A you are concerned with.

Both approaches have their advantages and disadvantages, but for me option 2 proved to be the better choice.