Hi all,

In my project, I use CASCADE to save, update or delete my objects.

For example,

class Node {
private Set incoming;
private Set outgoing;
public void addIncoming(Connection c);
public void removeIncoming(Connection c)
public void addOutgoing(Connection c);
public void removeOutgoing(Connection c);
}

class Connection {
private Node source;
private Node target;
//getters&setters
}

I wrote the hibernate mapping xml
<class name="Node">
<set name="outgoing" inverse="true" cascade="all-delete-orphan">
<key column="source"/>
<one-to-many class="Connection"/>
</set>
<set name="incomings" inverse="true" cascade="all-delete-orphan">
<key column="target"/>
<one-to-many class="Connection"/>
</set>
</class>

When I do this,
node1.removeIncoming(c1);
node2.addIncoming(c1);
c1.setTarget(node2);

while the objects tree in memory is

root
/ | \
/ | \
node1 node2 node3

all operations on root has been cascaded on it's children

When I call

session.saveOrUpdate(root);

I hope c1 will be saved with target, node2.

But the excetion is throwed:
net.sf.hibernate.HibernateException: Flush during cascade is dangerous - this might occur if an object was deleted and then re-saved by cascade

How to avoid this?

Furthemore,
I wonder whether "cascade=all-delete-orphan" could help me not to call
session.delete?

Best regards!

Jun Huang

you can't use orphan delete in this kind of situation. Orphan delete means: "when this object is removed from the collection, _delete_it_".

Thanks a lot, gavin!

But, in fact,

I implement LifeCycle's method -- onDelete(), on class Connection

public boolean onDelete(Session s) throws CallbackException {
//judge if the connection could be deleted

//in my situation, only target changed,
//so the connection should not be deleted, return true
return sourceAttached && targetAttached;
}

That works fine when I change the source of connection.

However, when I change the target of connection, the connection could
not be saved with it's new target. :-(

I will keep on checking my code.

Best regards,

Jun Huang

Ah! Interesting.

That should theoretically work, though I've never tried anything like that.

Still, *somehow* the object is being marked deleted. Are you _certain_ the lifecycle method is called and is returning true?

Step through the code, esp. with Hibernate logging enabled.

quite strange!

I found that if I call session two times, the target will be saved correctly!
(with two different sessions)

Best regards,

Jun Huang

I was able to use the Lifecycle interface as mentioned to successfully move a child between parents. The child collection is still mapped as 'all-delete-orphan'.