Again, I have Tool and Copmany. Every tool belongs to exactly one company. Mapping for Company:

<set name="tools" inverse="true">
<key column="COMPANY_ID"/>
<one-to-many class="eg.Tool"/>
</set>

Mapping for Tool has:

<many-to-one
name="company"
class="eg.Company"
column="COMPANY_ID"
outer-join="false"
not-null="true"
/>


note "not-null". When I try

session.save( new Tool() );

I get Not null constraint violation from Oracle, not from Hibernate. This is bacause Hibernate actually tried to insert record into the TOOL table. The question is: why? IMHO, Hibernate should check not-null constraints it knows about before submitting anything into database..

(I have Hibernate 2.0.3)

The "not-null" attribute is only used for schema generation. It will apply a NOT NULL constraint to the specified column.

Hibernate does not use this value to perform any type of validation.

Why not?

I think implementing such a check is very cheap. And more strict checking is always better.

What would be the value, exactly?

A better exception message maybe .... but I can't see much more than that ...

I'm talking exactly about better exception message. Just to ease debugging.

It is much better when Hibernate tells "hey, you are doing something wrong - non-null property XXX of class YYY is null" than to dig through JDBC exception stack trace.

Different JDBC drivers may report the same problem with different diagnostics. And after all, not all JDBC drivers are verbose enough to explain what is wrong.

(For example, when you put string into NUMBER column, Oracle JDBC driver just says "invalid number" leaving to you guessing which column caused problem).