Help HIGHLY needed with one-to-one mapping error

[Ruben Matthews]

Hi,

I am running into a much discussed error with a one-to-one mapping, but I just can't getting fixed! I keep running into the following error:

Exception in thread "main" org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property [nl.xx.yy.zz.model.UserSession.user]

I am trying to tie a UserSession to an AbstractUser in a one-to-one relationship using a foreign key association.

This is the mapping for the AbstractUser:

<hibernate-mapping package="nl.xx.yy.zz.model">
	<class name="AbstractUser" table="SM_USER">
		<id name="userId" type="integer" column="USER_ID">
			<generator class="native" />
		</id>

		<one-to-one name="userSession" class="UserSession" cascade="all"/>

		<property name="username" type="string" column="USERNAME"
			unique="true" />
		<property name="password" type="string" column="PASSWORD" />

	</class>
</hibernate-mapping>

This is the mapping for the UserSession:

<hibernate-mapping package="nl.xx.yy.zz.model">
	<class name="UserSession" table="SM_USERSESSION">
		<id name="sessionId" column="SESSION_ID">
			<generator class="foreign">
				<param name="property">user</param>
			</generator>
		</id>
		
		<one-to-one name="user" class="AbstractUser" constrained="true" />
		
		<property name="UUID" type="string" not-null="true" length="40" column="UUID" />
		<property name="loginDate" type="date" not-null="true" column="LOGIN_DATE" />

	</class>
</hibernate-mapping>

And this is the code I use:

Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
AbstractUser user = null;
List userList = session.createQuery("from AbstractUser au where au.username = :username")
	.setString("username", "myUserName")
	.list();

if (userList.size() > 0)
	user = (AbstractUser) userList.get(0);	
		
// Compare (encrypted) passwords
if(user != null && user.getPassword().equals("myPassWord")){
	// Authentication succeeded!
	
	// Create a new UserSession for this user		
	UserSession ses = new UserSession();			
	// Generate the session id
	String uuid = UUID.randomUUID().toString();
	ses.setUUID(uuid);
	ses.setLoginDate(new Date());
	// Set the UserSession on the user
	user.setUserSession(ses);
	// Save/Update
	session.update(user);		
}
// Commit
session.getTransaction().commit();

This throws the "attempted to assign id from null one-to-one property" error. Do you know why and how to solve this? The problem occurs on the session.update(user). All the surrounding code works fine.

Also, when I use session.save() instead of session.update, Hibernate tries to insert a new AbstractUser record with the same id, resulting in a PK constraint failure. Why is Hibernate tryuing to insert a new record instead of just updating the existing one?

[pandya devarshi r]

Hi Ruben,

Your save operation is working fine but exception is throw in update operation because of sessionId property of UserSession object store the null value.

Save() operation is working fine because hibernate generate the incremented value for sessionId property but this is not true about update() operation. You should explicitly assigned the sessionId value. If I am not wrong then get the value from userlist and assigned to the sessionId property.

If you have any query/exception regarding this suggestion please inform me.

Thanks&Regards
Devarshi