Fluent NHibernate:映射复杂的多对多(带有附加列)并设置fetch

我需要一个流利的NHibernate映射,它将实现以下功能(如果没有其他功能,我还将使用适当的NHibernate XML映射并对其进行反向工程)。

细节

我在两个实体之间有一种多对多的关系: Parent 和 Child

这大概就是我定义类型的方式,至少是相关的部分(其中 Entity Id

public class Parent : Entity
{
    public virtual IList<ParentChildRelationship> Children { get; protected set; }

    public virtual void AddChildRelationship(Child child, int customerId)
    {
       var relationship = new ParentChildRelationship
                        {
                           CustomerId = customerId,
                           Parent = this,
                           Child = child
                        };
       if (Children == null) Children = new List<ParentChildRelationship>();
       if (Children.Contains(relationship)) return;
       relationship.Sequence = Children.Count;
       Children.Add(relationship);
    }
}

public class Child : Entity
{
    // child doesn't care about its relationships
}

public class ParentChildRelationship
{
    public int CustomerId { get; set; }
    public Parent Parent { get; set; }
    public Child Child { get; set; }
    public int Sequence { get; set; }

    public override bool Equals(object obj)
    {
       if (ReferenceEquals(null, obj)) return false;
       if (ReferenceEquals(this, obj)) return true;
       var other = obj as ParentChildRelationship;
       if (return other == null) return false;

       return (CustomerId == other.CustomerId
           && Parent == other.Parent
           && Child == other.Child);
    }

    public override int GetHashCode()
    {
       unchecked
       {
           int result = CustomerId;
           result = Parent == null ? 0 : (result*397) ^ Parent.GetHashCode();
           result = Child == null ? 0 : (result*397) ^ Child.GetHashCode();
           return result;
       }
    }
}

数据库中的表大致如下(假定主键/外键和语法):

create table Parent (
   id int identity(1,1) not null
)

create table Child (
   id int identity(1,1) not null
)

create table ParentChildRelationship (
   customerId int not null,
   parent_id int not null,
   child_id int not null,
   sequence int not null
)

在访问Parent.Children时,NHibernate应该生成一个等价的查询:

SELECT * FROM ParentChildRelationship rel LEFT OUTER JOIN Child ch ON rel.child_id = ch.id WHERE parent_id = ?

好的,我有这样的映射:

ParentMap : ClassMap<Parent>
{
   public ParentMap()
   {
      Table("Parent");
      Id(c => c.Id).GeneratedBy.Identity();
      HasMany(c => c.Children).KeyColumn("parent_id");
    }
}

ChildMap : ClassMap<Child>
{
   public ChildMap()
   {
      Table("Child");
      Id(c => c.Id).GeneratedBy.Identity();
   }
}


ParentChildRelationshipMap : ClassMap<ParentChildRelationship>
{
   public ParentChildRelationshipMap()
   {
      Table("ParentChildRelationship");
      CompositeId()
                .KeyProperty(c => c.CustomerId, "customerId")
                .KeyReference(c => c.Parent, "parent_id")
                .KeyReference(c => c.Child, "child_id");
      Map(c => c.Sequence).Not.Nullable();
    }
}

所以,在我的测试中,如果我想 myParentRepo.Get(1).Children parent.Children.Select(r => r.Child).ToList() ).

SELECT * FROM ParentChildRelationship WHERE parent_id = 1 然后是一个 SELECT * FROM Child WHERE id = ? 每段关系中的每个孩子。我理解NHibernate为什么要这样做,但是我不知道如何设置映射以使NHibernate按照我上面提到的方式进行查询。