流利的 NHibernate 多对多与额外的列不插入

Question

我正在努力使用来自 Fluent Nhibernate Many-to-Many mapping with extra column 的流畅的 nhibernate

我已经复制了映射并编写了我能写的最小的程序……但它不会保存……有人能提供一些见解吗？？？

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public IList<Inventory> Inventory { get; set; }

    public Product()
    {
        Inventory = new List<Inventory>();
    }
}

public class Warehouse
{
    public int Id { get; set; }
    public string Name { get; set; }
    public IList<Inventory> Inventory { get; set; }

    public Warehouse()
    {
        Inventory = new List<Inventory>();
    }
}

public class Inventory
{
    public Product Product { get; set; }
    public Warehouse Warehouse { get; set; }
    public bool StockInHand { get; set; }


    // override object.Equals
    public override bool Equals(object obj)
    {
        if (obj == null || GetType() != obj.GetType())
        {
            return false;
        }
        var i = obj as Inventory;

        return ((i.Product.Id == this.Product.Id) 
             && (i.Warehouse.Id == this.Warehouse.Id));
    }

    // override object.GetHashCode
    public override int GetHashCode()
    {
        return 9999;
    }
}
public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Not.LazyLoad();
        Table("Product");
        Id(x => x.Id).GeneratedBy.Assigned();
        Map(x => x.Name);
        HasMany(x => x.Inventory).AsBag()
         .Cascade.All()
         //.Inverse()
         .Table("Inventory");
    }
}
public class WarehouseMap : ClassMap<Warehouse>
{
    public WarehouseMap()
    {
        Not.LazyLoad();
        Table("Warehouse");
        Id(x => x.Id).GeneratedBy.Assigned();
        Map(x => x.Name);
        HasMany(x => x.Inventory).AsBag()
         .Cascade.All()
         .Inverse()
         .Table("Inventory");
    }
}
public class InventoryMap : ClassMap<Inventory>
{
    public InventoryMap()
    {
        Not.LazyLoad();
        Table("Inventory");
        CompositeId()
          .KeyReference(x => x.Product, "Product_id")
          .KeyReference(x => x.Warehouse, "Warehouse_id");

        Map(x => x.StockInHand);
    }
}

还有程序...

using (var session = sessionFactory.OpenSession())
{
    using (var transaction = session.BeginTransaction())
    {
        Product p = new Product() { Id = 1, Name="product" };
        Inventory i = new Inventory() { StockInHand = true };
        i.Product = p;
        p.Inventory.Add(i);
        Warehouse w = new Warehouse() { Id = 1, Name = "warehouse" };
        i.Warehouse = w;
        w.Inventory.Add(i);

        session.SaveOrUpdate(p);

        session.Flush();

        transaction.Commit();
    }
}

我得到的例外是

constraint failed\r\nforeign key constraint failed

我还输出了 create 语句，这对我来说是正确的...

create table Inventory (
    Product_id INT not null,
   Warehouse_id INT not null,
   StockInHand BOOL,
   primary key (Product_id, Warehouse_id),
   constraint FK2B4C61665C5B845 foreign key (Product_id) references Product,
   constraint FK2B4C616A6DE7382 foreign key (Warehouse_id) references Warehouse)

create table Product (
    Id INT not null,
   Name TEXT,
   primary key (Id)
)

create table Warehouse (
    Id INT not null,
   Name TEXT,
   primary key (Id)
)

以及在异常之前运行的 SQL....

NHibernate:
INSERT
INTO
    Warehouse
    (Name, Id)
VALUES
    (@p0, @p1);
@p0 = 'warehouse' [Type: String (0)], @p1 = 1 [Type: Int32 (0)]
NHibernate:
INSERT
INTO
    Inventory
    (StockInHand, Product_id, Warehouse_id)
VALUES
    (@p0, @p1, @p2);
@p0 = True [Type: Boolean (0)], @p1 = 1 [Type: Int32 (0)], @p2 = 1 [Type: Int32 (0)]

那么这应该如何正常工作？！？

Answer 1

您的问题的原因是 NHibernate 试图在 Warehouse 记录之前插入 Inventory 记录。这是因为插入的顺序由调用session.Save 的顺序决定。基于此信息，我尝试了许多代码变体来防止外键约束错误。我在下面发布了我最好的解决方案。

using (var session = sessionFactory.OpenSession())
using (var transaction = session.BeginTransaction())
{
    var warehouse = new Warehouse() { Id = 1, Name = "warehouse" };
    session.Save(warehouse);

    var product = new Product() {Id = 1, Name = "product"};
    var inventory = new Inventory 
                     { StockInHand = true, Product = product, Warehouse = warehouse};

    product.Inventory.Add(inventory);
    warehouse.Inventory.Add(inventory);

    session.Save(product);

    transaction.Commit();
}

我发现的一件让我相当吃惊的事情是，如果你把session.Save(warehouse) 放在warehouse.Inventory.Add(inventory) 之后，那么NHibernate 不会先插入Warehouse 记录，并且会抛出外键错误。

最后一点，要获得下面列出的三个插入语句，Inverse() 必须在 ProductMap 映射类中重新设置。否则 NHibernate 将发出一个额外的更新语句。

INSERT INTO Warehouse (Name, Id) VALUES (@p0, @p1);@p0 = 'warehouse' 
[Type: String (4000)], @p1 = 1 [Type: Int32 (0)]

INSERT INTO Product (Name, Id) VALUES (@p0, @p1);
@p0 = 'product' [Type: String (4000)], @p1 = 1 [Type: Int32 (0)]

INSERT INTO Inventory (StockInHand, Product_id, Warehouse_id) VALUES (@p0, @p1, @p2);
@p0 = True [Type: Boolean (0)], @p1 = 1 [Type: Int32 (0)], @p2 = 1 [Type: Int32 (0)]

Answer 2

对于任何可能追随我脚步的人......

我的问题是我想在链接表中存储有关实体之间关系的一些信息。传统上，数据库术语中的多对多关系在域对象之间有一个链接表。

根据问题中概述的结构，需要先插入仓库和产品，然后才能插入库存项目。必须最后插入 Inventory 项目，以便在保存之前两个外键约束都到位。

Insert into Product

Insert into Warehouse

Insert into Inventory (Note this happens **after** the primary keys are 
inserted in Warehouse and Product!)

但是，我使用 Fluent NHibernate 生成以下映射...

Insert into Product

Insert into Inventory (Foreign Key constraint violated, no Warehouse)

.. 这一定是不正确的，因为仓库没有主键！我了解问题，但不了解解决方案...我已经设法产生了如下两个解决方案，但我认为两者都不是最佳的。

public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Not.LazyLoad();
        Table("Product");
        Id(x => x.Id, "Product_id").GeneratedBy.Assigned();
        Map(x => x.Name).Column("Name").Length(10);
        HasMany(x => x.Inventory)
            .Cascade.Delete()
            .KeyColumn("Product_id");
    }
}
public class WarehouseMap : ClassMap<Warehouse>
{
    public WarehouseMap()
    {
        Not.LazyLoad();
        Table("Warehouse");
        Id(x => x.Id, "Warehouse_id").GeneratedBy.Assigned();
        Map(x => x.Name).Column("Name").Length(10);
        HasMany(x => x.Inventory)
            .Cascade.All()
            .KeyColumn("Warehouse_id");
    }
}
public class InventoryMap : ClassMap<Inventory>
{
    public InventoryMap()
    {
        Not.LazyLoad();
        Table("Inventory");
        CompositeId()
          .KeyReference(x => x.Product, "Product_id")
          .KeyReference(x => x.Warehouse, "Warehouse_id");
        Map(x => x.StockInHand);
    }
}

我可以执行保存并让一半的代码按预期工作，但它以序数为前提。即，我必须了解这些对象需要保存的顺序。我还没有测试过删除会发生什么，但这确实意味着我必须按照正确的顺序来保存这些对象。 /* 工作 */ session.Save（产品）； session.Save(仓库); // 也会保存库存

/* would fail */
session.Save(warehouse);
session.Save(product);

或者（我更不喜欢这个）我可以告诉 Nhibernate 我想对所有事情负责......

public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Not.LazyLoad();
        Table("Product");
        Id(x => x.Id, "Product_id").GeneratedBy.Assigned();
        Map(x => x.Name).Column("Name").Length(10);
        HasMany(x => x.Inventory).Inverse();
    }
}
public class WarehouseMap : ClassMap<Warehouse>
{
    public WarehouseMap()
    {
        Not.LazyLoad();
        Table("Warehouse");
        Id(x => x.Id, "Warehouse_id").GeneratedBy.Assigned();
        Map(x => x.Name).Column("Name").Length(10);
        HasMany(x => x.Inventory).Inverse();
    }
}
public class InventoryMap : ClassMap<Inventory>
{
    public InventoryMap()
    {
        Not.LazyLoad();
        Table("Inventory");
        CompositeId()
          .KeyReference(x => x.Product, "Product_id")
          .KeyReference(x => x.Warehouse, "Warehouse_id");
        Map(x => x.StockInHand);
    }
}

现在我得到以下内容

/* works */
session.save(Product);
session.Save(Warehouse);
session.Save(Inventory);

/* works */
session.Save(Warehouse);
session.Save(Product);
session.Save(Inventory);

/* fails */
session.Save(Inventory);
session.Save(Warehouse);
session.Save(Product);

任何人都可以对此进行改进并给我我真正想要的映射，这样我就可以保存一个仓库或一个产品和 Fluent NHibernate，这将使订购正确！?? 例如。

session.Save(warehouse); // or session.Save(product);

这样会导致

Insert into Warehouse... 
Insert into Product...
Insert into Inventory... // where NHibernate determines this goes last so that primary keys are in place on both previous tables!