Hello,


Trying my first test with Hibernate, I used HibernateSynchroniser to generate the mapping file of a simple table (ID, text).

Hibernate Synchroniser gives me a <generator class="vm" /> for the primary key. I changed this to "identity" (as the manual said for SQL Server).

I didn't find anything about <generator class="vm" /> on the forum or in the online docs.

My problem is that I can't insert anything if I use <generator class="identity" /> (or "native") but it's okay with <generator class="vm" />.

Below, I provide the Stack trace and the generated SQL.

My question is : What is <generator class="vm" /> ???


Hibernate version: 2.1.6

Mapping documents:
<hibernate-mapping package="test">
<class name="TauxTva" table="TAUXTVA">
<id
column="TauxTVAID"
name="id"
type="int"
>
<generator class="identity" />
</id>
<property
column="TauxTVA"
length="53"
name="TauxTVA"
not-null="true"
type="float"
/>
</class>
</hibernate-mapping>


Full stack trace of any exception that occurs:
Caused by: java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]Can't insert NULL in column 'TauxTVAID', table 'TEST.dbo.TAUXTVA'. This column doesn't accept NULL value. INSERT a

Another question could be : Why "native" and "identity" don't work ?

I have the same behaviour and the same questions. Anyone know?

L

In fact, it works.

Here, I switched to "native" for IDs and it works.

In fact, it was our fault : we didn't select the primary key in the table panel to be automatically incremented.

I think generator="vm" means "Select max(id)" and do (max+1) for insert(id, ...)

Generator="native" relies on SQL Server to produce a valid ID.

vm = increment, they are the same. use of the term vm is deprecated.

native is meant for portability. it says to use the capabilities supported by the underlying database. for sql-server, this would translate into the use of the IdentityGenerator class, which relies on the databases ability to mark the pk column for auto-increment.

Thanks Steve, for the answer.