NHibernate 在合并之前保存嵌套的瞬态对象

Question

Is there a way to save transient objects within a nested object.

The problem is that the object reference is not the same as within the session due to the fact that the model comes from a deserialized json and then projected into entities. Therefore i need to use Merge on the NHibernate session.

Lets say we have this simplified model.

class Product
{
    public int Id {get; protected set;}
    Public List<ProductVariant> ProductVariants {get; set;}
}
class ProductVariant
{
    public int Id {get; protected set;}
    //more stuff nested deeper
}

Saving of the object contains

Product -> id = 1
        -> ProductVariants -> ProductVariant -> id = 1
                           |> ProductVariant -> id = 2
                           |> ProductVariant -> id = 0 //Transient object

so:

session.SaveOrUpdate(Product) //wont work, different object reference to the same identity
session.Merge(Product) //Wont work, there is a transient object

I knoew that i could proberbly just do something like:

Foreach (productVariant : Product.ProductVariants){
    if( productVariant.Id == 0)
        sessiont.save(productVariant);
}
session.Merge(Product);

But isn't there a way to tell, Merge that if transient object just save ?

Cause lets say that the object that you would like to save is deeply nested, it would kinda suck to step through the entire nested object just to look for Ids that is 0

Edit:

Looks like i could override the equals method to check if the Id is the same, and is of same type of object, but something in me says its a bad idea. Even though set Id is protected. However having overrriden the Equals methods means that i can use SaveOrUpdate, which is preferable.

like:

class Product
{
    public int Id {get; protected set;}
    Public List<ProductVariant> ProductVariants {get; set;}

    public override bool Equals(Object obj) 
    {

       if (obj == null || GetType() != obj.GetType()) 
       return false;

       Product otherProduct = (Product)obj;
       return otherProduct.Id == Id
    }
}
class ProductVariant
{
    public int Id {get; protected set;}
    //more stuff nested deeper
    public override bool Equals(Object obj) 
    {

       if (obj == null || GetType() != obj.GetType()) 
       return false;

       ProductVariant otherProduct = (ProductVariant)obj;
       return otherProduct.Id == Id
    }
}

Atleast that what they say here: http://nhibernate.info/blog/2009/08/23/part-5-fixing-the-broken-stuff.html under problem #2

Answer 1

You need to cascade the ProductVariants list in the mapping of Product . NHibernate will adding the new ProductVariant if it is not persisted already.

If everything is set up correctly you don't need to call then any SaveOrUpdate() or Merge() method.

Answer 2

If your still having problems with cascading there, and saving/updating a entity that has children entities created by your view and they have a id of 0, you will also get this message. So null our before saving/updating the child entity, if it's empty (not required or any input entered) and this will also resolve this problem.