I had a similar issue back in April in the past. I believe you can work
around this limitation by committing the parent of the relationship (the
"one" of the "one-to-many") before committing the children (the "many").
http://cayenne.markmail.org/message/6nazm7w4kaxxhj7m
-----Original Message-----
From: Michael Shea [mailto:mik..itido.com]
Sent: Wednesday, November 19, 2008 6:11 PM
To: use..ayenne.apache.org
Subject: Order of commits?
Hi guys -
I am wondering if there is any way to tell cayenne what order to commit
new objects in.
My issue is basically like this:
Suppose I have Category objects and Item objects.
A user can pass in a CategoryDescriptor, which contains a list of
ItemDescriptors. I want cayenne to generate, from these descriptors, the
corresponding database-model objects and rows in the database. So I do
something like this:
public Category createCategory( CategoryDescriptor categoryDescriptor )
{
Context context = ...; // do something to get the context here.
Category category = context.newObject( Category.class );
.... // fill in stuff about the category object here.
for ( ItemDescriptor itemDescriptor :
categoryDescriptor.getItemDescriptors() )
{
Item item = context.newObject( Item.class );
... // fill in stuff about the item object here.
}
context.commitChanges();
return Category;
}
The problem I am having is that both Category and Item have primary keys
which are autogenerated by database (I am using MySQL, the ID's are
generated via AUTO_INCREMENT columns). It looks like cayenne is
attempting to create the Item objects before creating the Category
object, and then it's giving me a commit exception like this:
org.apache.cayenne.CayenneRuntimeException: [v.3.0M4 May 18 2008
16:32:02] Commit Exception
at
org.apache.cayenne.access.DataContext.flushToParent(DataContext.java:119
2)
at
org.apache.cayenne.access.DataContext.commitChanges(DataContext.java:106
6)
at com.nitido.rss.RSSNugget.createCategory(RSSNugget.java:294)
...
Caused by: com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Table
'rss.AUTO_PK_SUPPORT' doesn't exist
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1026)
...
It looks like, since the ID on the Item is null and the Category object
hasn't been initialized yet, Cayenne is trying to generate an ID for the
row. I don't see any other INSERT commands from the logger after I call
context.commitChanges(), so the attempt to insert a row for the Item
object looks to be the first thing that it's trying to do.
So, my questions are:
1. Is this normal? Or does this sound like it could be a problem caused
by me screwing up the mapping.xml?
3. Is it a good idea to work around this by using either AUTO_PK_SUPPORT
or a custom database sequence, and forget about the AUTO_INCREMENT
feature? I have control over the database schema, so I could do this
instead. Alternately, I could just generate my own ID's without using
cayenne, but I'd rather not.
4. Is it normal to do this by committing the Category objects before
attempting to create Item objects related to them? That seems somewhat
hacky to me, though.
BTW, I'm using Cayenne 3.0M4.
Thanks!
Shea.
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