title: Hibernate Strange "ORA-01400: cannot insert NULL into" Error
body: <p>there is a strange error ocurring to me. I'm working with Hibernate, I have mapped class called Widget, which has a Parameter class, but when I try to insert I get
  "ORA-01400: cannot insert NULL into..."</p>
  
  <p>The mapping is properly done as:</p>
  
  <pre><code>&lt;bag cascade="none" inverse="true" lazy="false" name="parameters" table="PARAMS" &gt;
    &lt;key column="WIDGET_ID" foreign-key="FK_PARAMS" not-null="true"/&gt;
    &lt;one-to-many class="Parameter"/&gt;
  &lt;/bag&gt;
  </code></pre>
  
  <p>The wierd thing is that the not-null property is setted to "true" which forces to insert the ID value of the Widget Object.</p>
  
  <p>Thanks in advance</p>