Exploring nhibernate mapping

Question

A code generator needs to extract and generate some metadata from nhibernate mappings, I am wondering how nhibernate store relations.

For many to one relation how the o

Answer 1

Configuration, and later ISessionFactory build from it, are keeping information about persisters. They could represent entities or collections.

Here we can see what we could get about any persisted class:

• How do you get the database column name

The class persister:

var entityType = typeof(TEntity);
var factory = ... // Get your ISessionFactory
var persister = factory.GetClassMetadata(entityType) as AbstractEntityPersister;

And we also can observe collection persisters

• Test a collection is Many to many or many to one

the collection persister:

// the Abstract collection persister
var collectionPersister = factory
    .GetCollectionMetadata(roleName) as AbstractCollectionPersister;

// here we go:
var isManyToMany = collectionPersister.IsManyToMany;
var isOneToMany = collectionPersister.IsOneToMany;

So, in general, what is mapped, it is represented as persister. Hope it helps

EXTEND, find out one-to-one

Based on the stuff above, the explicit search for one-to-one could be like:

var persister = factory.GetClassMetadata(entityType) as AbstractEntityPersister;
var propertyNameList = persister.PropertyNames;

foreach (var propertyName in propertyNameList)
{
    // many info is in collections, so we need to know the index
    // of our property
    var index = persister.GetPropertyIndex(propertyName);

    // with index, we can work with the mapped type
    var type = persister.PropertyTypes[index];

    // if the type is OneToOne... we can observe
    if(type is NHibernate.Type.OneToOneType)
    {
        Console.Write(type.IsAssociationType);
        Console.Write(type.IsAnyType);
        Console.Write(type.IsMutable);
        Console.Write(type.IsCollectionType);
        Console.Write(type.IsComponentType);
        Console.Write(type.ReturnedClass);
        ...
        // many other interesting and useful info could be revealed
    }
}