Hi, I'm facing a problem with many-to-many relation, especially in the generation of the primary key for the association table.
I'm quite new to hibernate and I'm experimenting with its many features...

In my db I have an Order, a Product and an OrderLine tables. The OrderLine table has a composite key (orderId, productId) and two more fields, amount and price.
I developed an application that inserts new products without any problem.
But when I try to create a new Order I get an exception with this message:
ids for this class must be manually assigned before calling save(): OrderLine.
I can understand what hibernate is trying to tell me, in fact I don't explicitly assign the ids... I guess hibernate can handle this work for me, but as I said, I'm a newbie!

Thanks!

Hibernate version: 3.0.5

Mapping documents:
------ Mapping for class Order -------
<hibernate-mapping>
<class name="Order" table="Order">
<id name="id" type="integer">
<column name="id" />
<generator class="increment" />
</id>
<property name="orderDate" type="date">
<column name="orderDate" length="10" not-null="true" />
</property>
<property name="totalPrice" type="double">
<column name="totalPrice" precision="22" scale="0" not-null="true" />
</property>
<set name="orderLines" table="OrdineLine" inverse="true" cascade="save-update" >
<key column="orderId"/>
<one-to-many class="OrderLine"/>
</set>
</class>
</hibernate-mapping>

------ Mapping for class Product -------
<hibernate-mapping>
<class name="Product" table="Product">
<id name="id" type="integer">
<column name="id" />
<generator class="increment" />
</id>
<property name="nome" type="string">
<column name="name" length="50" not-null="true" />
</property>
<property name="price" type="double">
<column name="prce" precision="22" not-null="true" />
</property>
</class>
</hibernate-mapping>

------ Mapping for class OrderLine -------
<hibernate-mapping>
<class name="OrderLine" table="OrderLine">
<composite-id name="id" class="OrderLineId">
<key-property name="orderId" type="integer">
<column name="orderId" />
</key-property>
<key-property name="productId" type="integer">
<column name="productId" />
</key-property>
</composite-id>
<property name="amount" type="integer">
<column name="amount" not-null="true" />
</property>
<property name="price" type="double">
<column name="price" not-null="true" />
</property>
<many-to-one name="product" class="Product" insert="false" update="false">
<column name="productId" />
</many-to-one>
<many-to-one name="order" class="Order" insert="false" update="false">
<column name="orderId" />
</many-to-one>
</class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():
Product p = null;

Query q = sess.createQuery("from Product p where p.name = 'Milk'");
List<Product> ql = q.list();
if(ql.size() > 0)
p = ql.get(0);

Transaction t = sess.beginTransaction();

Order o = new Order();
o.setOrderDate(new Date());
o.addProduct(p, 5); //Adds an OrderLine with 5 products
sess.persist(o);
t.commit();

Full stack trace of any exception that occurs:
Exception in thread "main" org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save(): OrderLine
at org.hibernate.id.Assigned.generate(Assigned.java:32)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:85)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:184)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:173)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:96)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:69)
at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:468)
at org.hibernate.engine.Cascades$5.cascade(Cascades.java:154)
at org.hibernate.engine.Cascades.cascadeAssociation(Cascades.java:771)
at org.hibernate.engine.Cascades.cascade(Cascades.java:720)
at org.hibernate.engine.Cascades.cascadeCollection(Cascades.java:895)
at org.hibernate.engine.Cascades.cascadeAssociation(Cascades.java:792)
at org.hibernate.engine.Cascades.cascade(Cascades.java:720)
at org.hibernate.engine.Cascades.cascade(Cascades.java:847)
at org.hibernate.event.def.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:121)
at org.hibernate.event.def.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:112)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:59)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:730)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:324)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:86)
at insertOrder.main(insertOrder.java:44)

Name and version of the database you are using: Mysql 4.1.9

I belive you want to remove the insert=false and update=false attributes from your Product and Order mappings:



You are telling Hibernate to not set those values when you add an OrderLine, so it has nothing from which to make the composite-id.

I am no expert on composite-ids, though, so could be totally off base.

-----
Eric

Helpful? Hit me with a credit!

Thank you, but if I remove the insert="false" and/or update="false" attributes I get this exception:


donnie