PersistenceSpecification and inverse

Question

I've already posted this in the Fluent NH group a long time ago, but didn't get any answers until today. SO, here's the problem: I've got a one-to-many relationship defined and the one side has the inverse flag set. the mapping code looks something like this:

public class MapeamentoReceita : ClassMap<Receita> {
    public MapeamentoReceita() {
        Table("Receitas");
        Not.LazyLoad();

        Id(rec => rec.Id, "IdReceita")
            .GeneratedBy
            .HiLo("TabelaHilo", "ProximoHi", "1000", "Tabela='receitas'")
            .Default(0);
        Version(rec => rec.Versao);

        //other props go here
        HasMany(rec => rec.Imagens)
            .Access.CamelCaseField((Prefix.Underscore))
            .AsBag()
            .Cascade.All()
            .KeyColumn("IdReceita")
            .Not.LazyLoad()
            .Inverse();
    }
}

Now, Imagem's mapping looks like this:

 public class MapeamentoImagem : ClassMap<Imagem> {
    public MapeamentoImagem() {
        Table("Imagens");
        Not.LazyLoad();
        Id(img => img.Id, "IdImagem")
            .GeneratedBy
            .HiLo("TabelaHiLo", "ProximoHi", "1000", "Tabela='imagens'")
            .Default(0);
        Map(img => img.Bytes)
            .CustomSqlType("image")
            .CustomType<Byte[]>()
            .LazyLoad()
            .Length(2000000000)
            .Not.Nullable()
            .Not.Update();

        References(img => img.Receita)
            .Column("IdReceita")
            .Cascade.None();
    }
}

And here's the code that tests the persistence of these classes:

 new PersistenceSpecification<Receita>(sess)
    .CheckList(rec => rec.Imagens, 
               _imagens, 
               (receita, imagem) => receita.AdicionaImagem(imagem))
    .VerifyTheMappings();

Even though Inverse is "on", PersistenceSpecification tries to insert Imagem before inserting Receita. Since IdReceita is foreign key configured not to accept null, I end up with an exception. I've tried writing "real world code" that uses receita and it works (I've turned on SQL and I can see that in this case, Receita is inserted before Imagem as it should be).

Since nobody answered this question on FH group, I was wondering if someone can please confirm that this PersistenceSpecification behavior is a bug.

thanks.

Answer 1

Have you tried it this way?:

var receita = BuildMeAReceita();
var imagems = BuildSomeImagems();
foreach(var imagem in imagems){
    receita.AdicionaImagem(imagem);
}
new PersistenceSpecification<Receita>(sess)
.VerifyTheMappings(receita);

Answer 2

Try:

    References(img => img.Receita)
        .Column("IdReceita")
        .Not.Nullable();

My guess is that your real world code saves Recieta first so that the inserts are issued in the correct order. If you changed that code to save Imagem first you would get the same error because NHibernate would attempt to insert Imagem then update it with the foreign key.

Answer 3

You could change your mapping of Imagem

References(img => img.Receita)
            .Column("IdReceita")
            .Cascade.SaveUpdate();

This will persist Receita before Imagem

What I've found is that PersistanceSpecification works well for fairly straight forward relationships but if you have complex object graphs you have to have cascading turned on all of your objects. Your scenario is fairly simple though so this small change should allow you to test this using PersistanceSpecification.

Edit:

Also make sure in your AdicionaImagem function you are setting the parent of the image. Here is an example:

public virtual void AdicionaImagem(Imagem newImagem)
{
    newImagem.Receita = this;
    imagems.Add(newImagem);
}

Answer 4

There are two possible issues in your code.

1. Imagem.Bytes property is lazy-loaded but lazy loading for Imagem istself is disabled. It means no proxy is generated for Imagem instances and Bytes cannot be lazy-loaded: mission impossible (at least it appears to me right now, not sure). Simple load from database (session.Get<Imagem>(id);) leads to exceptions like this: Invalid Cast (check your mapping for property type mismatches); setter of Imagem. Solution is to enable lazy-loading on Imagem or disable lazy loading on Bytes property.
2. PersistenceSpecification loads tested entity from database as another instance. It means that default equality comparer does not work well. You need to provide your own equality comparer to solve this issue (check this for more details).

Here is Receita and Imagem entities, implementation of IEqualityComparer and PersistentSpecification snippet. This code works well in NH3.1 and FNH 1.2. Please, let me know if your code differs somehow from these snippets.