Hi folks,

I'm trying to leverage the default column values in my database through Hibernate, but I can't determine the right XML to use in my mapping file. Here's the situation.

The column bar in the table foo is defined as:



As you can see, the column does not allow nulls and has a default value.

I have an object foo, with getBar() and setBar(java.lang.String) methods. If I try to persist the object foo when foo.getBar() returns null, I want Hibernate to not send an explicit null for column bar to the database. This would allow the database to set column bar to value 'tic'.

Is it possible to configure this behavior in the Hibernate mapping file for table foo? I have this property for column bar:



I checked the documentation and saw the insert=false attribute for the property tag, but when I tried it foo.setBar('toe') has no effect when foo is persisted, meaning the column will always have value 'tic'.

Alternatively, a less desirable solution is for the Hibernate to explicitly send the default value 'tic' when foo.getBar() returns null. I tried using the tag to do this, but to no avail.

Can someone please shed some light on this issue? It would be very helpful to see a working XML snippet.

Thanks very much in advance,
mers

Basically you need to tell Hibernate to not include the column when it is null. To do this - on the class tag specify dynamic-update="true" and dynamic-insert="true". That will allow the insert or update to not include any column that is null. By default this is false so Hibernate can pre-generate the insert and update SQL needed for the class.

Also look at the generated attribute on the property tag. You way want to use this on your default value columns as well.

HTH
Tom

Thanks!

I took a look at the dynamic-insert attribute for class and the generated attribute for property.

When I tested these out, I get this behaviour:

1. If I don't mark a property as generated, Hibernate doesn't issue a followup SELECT, and thus doesn't refresh the object with the default column value generated by the database.

2. If I do mark a property as generated, Hibernate defaults the property to non-insertable and non-updateable mode. This means Hibernate never sends the property to the database, so calling the object's setter for that property will have no effect when the object is persisted. Without a working setter, the default can never be overridden.

The latter point is documented here.

Not exactly desirable behaviour, eh?

Hibernate support for default columns is broken in my opinion. There is no obvious reason why generate forces non-insertable mode.