<class name="Order" table="ORDERS">
<id name="id" column="ID"/>
<set name="items" table="ITEMS" cascade="all">
<key column="ID"/>
<composite-element class="Item">
<property name="info1"/>
<property name="info2"/>
</set>
</class>

==============

public class Order
{
private String id;
private Set items;
/* getter and setter methods */
}

public class Item
{
private String info1;
private String info2;
/* getter and setter methods */
}


public class Main
{
public static void main (String [] args)
{
Session session = HibernateUtil.currentSession();
Transaction tx = session.beginTransaction();
try
{
Order order = (Order) session.get(Order.class, "12");
order.getItems().remove(new Item(1));
/* just removed one element from the collection! */
tx.commit();

}
catch (Exception e)
{}
finally
{
HibernateUtil.closeSession();
}
}
}
===============

I can see the SQL delete statement executes successfully in the debug log, but when I goto the database, the corresponding record is still exist..... Any idea??

instead of cascade = all

try cascade="all-delete-orphan"

also you might have to drop the relationship first before droping the parent.

I have changed cascade="all-delete-orphan", but I am still unable to delete an element in the collection. I am not goint to delete any Order objects. I just want to delete some Items object in the collection.

You are mapping Item as a composite-element in the set. That is, no identifier for each row. Hibernate figures out which row to delete by checking all properties to see if they are matched.

When you are issuing remove(new Item(1)), I am assuming you only set the value 1 to one property, where is the second one?

All the properties of Item should be not-null. Also you should implement equals() and hashCode() in Item.java.

new Item(1) is a constructor which requires a primary key as an argument. Both Item class and Order class have already implemented equals() and hashCode().

However if I perform the following:

order.setItems(new TreeSet());
tx.commit();

All item records associated with this order record are removed.

So In order to remove a record, do I need to do the following??

TreeSet set = new TreeSet();
Iterator it = order.getItems().iterator();
while (it.hasNext())
{
Item item = (Item) it.next();
if (item is not equal to the intend removed record)
set.add(item);
}

order.setItems(set);
tx.commit();

Do I really need to do all these just to remove a single record??

You are still confused by entity type versus value type. In your Order mapping file:


you are using value type for Item, that is, there is no such thing as primary key for an item. It seems to me what you are trying to do is a straightfoward unidirectional one-to-many association. Please read reference document on one-to-many association. If you still have problem, you can post back. Good luck!
[/code]

You are correct that Item is a value type. I should have said that property 'info1' is used to distinguish between Item objects. The constructor of Item class requires an argument for 'info1' property.

We are facing the same but without success.
The question is: how to remove an element from a collection? and from database?

Here is what you need to do to delete an item from collection

Item wanted = null;
Collection items = order.getItems();
Iterator iter = items.iterator();
while (iter.hasNext()){
Item item = (Item) iter.next();
if (item.id matches the one you want)
wanted = item;
}

items.remove(wanted);
order.setItems(items);

// close session



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Hope it Helps.

Ron
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Dont forget to rate !