Hibernate version: 1.0.2
Name and version of the database you are using:SQL Server 2000

Mapping documents:

Order:


Warehouse:


OrderItem:


Classes:







Code between sessionFactory.openSession() and session.close():


Full stack trace of any exception that occurs:



No exception occurs when changing the execution order to the following:



When creating the DB using SchemaExport, all tables are created as they should:
tOrder (PK: ID)
tWarehouse (PK: ID)
tOrderItem (PK: OrderID + WarehouseID)

1. Please help in solving out this exception. I want to be able to save the order + orderItems in one batch.
2. How should I implement Equals and GetHashCode in OrderItem (because of composite-id usage):
public override bool Equals(object obj)
public override int GetHashCode()

Thanks
Ruby

One problem I see is that you are only setting
order.OrderItems.Add(orderItem);

Set the Order property in the OrderItem as well before calling
session.Save(order);

If this does not help can you please post the SQL's being generated by NHib

Code section # 1 (save warehouse, save order, save OrderItem):


NHib Generated SQLs for code section # 1:
NHibernate: INSERT INTO dbo.tWarehouse (Name) VALUES (@p0); select SCOPE_IDENTITY()
@p0 = 'TestWarehouse'
NHibernate: INSERT INTO dbo.tOrder (Price) VALUES (@p0); select SCOPE_IDENTITY()
@p0 = '100'


Code section # 2 (save warehouse, batch save order + OrderItem with setting orderItem.Order = order):


NHib Generated SQLs for code section # 2:
NHibernate: INSERT INTO dbo.tWarehouse (Name) VALUES (@p0); select SCOPE_IDENTITY()
@p0 = 'TestWarehouse'
NHibernate: INSERT INTO dbo.tOrder (Price) VALUES (@p0); select SCOPE_IDENTITY()
@p0 = '100'
NHibernate: UPDATE dbo.tOrderItem SET Price = @p0 WHERE OrderID = @p1 AND WarehouseID = @p2
@p0 = '0'
@p1 = '1'
@p2 = '1'

Exception code section # 2:


Code section # 3 (save warehouse, batch save order + OrderItem without setting orderItem.Order = order):


NHib Generated SQLs for code section # 3:
NHibernate: INSERT INTO dbo.tWarehouse (Name) VALUES (@p0); select SCOPE_IDENTITY()
@p0 = 'TestWarehouse'
NHibernate: INSERT INTO dbo.tOrder (Price) VALUES (@p0); select SCOPE_IDENTITY()
@p0 = '100'
NHibernate: UPDATE dbo.tOrderItem SET Price = @p0 WHERE OrderID = @p1 AND WarehouseID = @p2
@p0 = '0'
@p1 = ''
@p2 = '1'

Exception code section # 3:



in code section 1 - no exception but the relation record (orderItem) is not saved
in code section 2 setting orderItem.Order = order cause changes in NHib's SQL (@p1 = '1'). SQLs look fine IMHO (but the exception occurs).
in code section 3 no setting orderItem.Order = order. Relevant NHib's SQL (@p1 = '').
in both code section 2 + 3 - exception occurs.

Is it because of the default implementation (in class OrderItem) of
public override bool Equals(object obj)
public override int GetHashCode()?

If yes, How should I implement it?


Thanks
Ruby

Seems like it never inserts orderitem?



It tries to update OrderItem but the orderItem is never inserted??

I would try to flush the session before starting transaction:

i.e.
session.Flush();
ITransaction transaction = session.BeginTransaction();

You might found that the NHibernate tries to insert order/orderitem before the transactions is started, because they are related to warehouse (which is saved already), and NHibernate tries to cascade updates/additions...

Gert

AND (and probably only): You MUST explicity call
session.Save(orderItem): NHibernate has no way to distinquish between persistent and new instances of OrderItem, as Your composite-Id does not have unsaved meaning

Gert

Gert,
I've tried it, and the only code sequence that makes it work was:




However, this code produced the following DB calls:



The code section:

cause the NHibernate: INSERT INTO dbo.tOrderItem....statement

The code section:

cause the NHibernate: UPDATE dbo.tOrderItem..... statement
If skipping this code, although the INSERT INTO dbo.tOrderItem....statement, no relation record created in the DB.

Very strange behaviour, I don't get it.
Ruby

Very starnge ineed... Did You try session.Flush() before StartTransaction?

OK,
I've changed Code Section 1 to 3 above to include the session.Flush() as Gert offered:

Section 1 with Flush()
[code]ISession session = sessionFactory.OpenSession();

Warehouse warehouse = new Warehouse();
warehouse.Name = "TestWarehouse";
session.Save(warehouse);

Order order = new Order();
order.Price = 100.0;
session.Save(order);

OrderItem orderItem = new OrderItem();
orderItem.Warehouse = warehouse;
orderItem.Order = order;
session.Save(orderItem);
session.Flush();

session.Close();

Section 2 with Flush()
[code]ISession session = sessionFactory.OpenSession();

Warehouse warehouse = new Warehouse();
warehouse.Name = "TestWarehouse";
session.Save(warehouse);

Order order = new Order();
order.Price = 100.0;

OrderItem orderItem = new OrderItem();
orderItem.Warehouse = warehouse;
orderItem.Order = order;
order.OrderItems.Add(orderItem);

session.Flush();
ITransaction transaction = session.BeginTransaction();
session.Save(order);
transaction.Commit();
session.Close();[/code]

Section 3 with Flush()
[code]ISession session = sessionFactory.OpenSession();

Warehouse warehouse = new Warehouse();
warehouse.Name = "TestWarehouse";
session.Save(warehouse);

Order order = new Order();
order.Price = 100.0;

OrderItem orderItem = new OrderItem();
orderItem.Warehouse = warehouse;
//orderItem.Order = order;
order.OrderItems.Add(orderItem);

session.Flush();
ITransaction transaction = session.BeginTransaction();
session.Save(order);
transaction.Commit();
session.Close();[/code]


Section 1 is working fine now. 2 and 3 not (exception still occurs) .
The conclusion:

To insert the orderItem (relation record) to the DB one must prepare it with proper refrences (orderItem.Warehouse = warehouse and orderItem.Order = order) save it, and flush the session (or do it inside of a transaction).

Any try to add it to the orderItems collection of the order object and than save the order + orderItem as a batch, will fail.

This is probably because of the <composite-id> ID

Thanks you Gert and samujob.

but it doesn't make to much sense, the trick is that order and orderItems should be saved with one batch: order.OrderItems.Add(orderItem); ...explicitly calling session.Save(orderItem) just partly destroys the idea of one-to-many mapping, more to assign explicitly PK with FK and we won't need one-to-many property at all (

I also came across this problem, implementing similar example:



Please help in solving out this exception using order.OrderItems.Add(orderItem) only.