[google-appengine] Updating problem with unkowned relation

[Bat]

I've 2 simple classes :

public class Student {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
   com.google.appengine.api.datastore.Key key;
@Persistent
   public String firstName;
@Persistent
   public String lastName;
}
And

public class Teacher {
    @PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    com.google.appengine.api.datastore.Key key;
    @Persistent
    public String firstName;
    @Persistent
    public String lastName;
    @Persistent
    public com.google.appengine.api.datastore.Key student;
}

First, I create a Teacher with only the fields 'firstname' &
'lastname' filled. It works. Then, I update my teacher with this
code :

Transaction tx = pm.currentTransaction();
  tx.begin();
  Teacher a = pm.getObjectById(Teacher.class,
KeyFactory.stringToKey( the_key));
  if(a != null) {
  try {
  a.setFirstName("test");
  a.setLastName("test");
  a.student = KeyFactory.stringToKey( req.getParameter("student101-
key"));
  tx.commit();
  }
  }
  pm.close();
  }
  }
After this transaction, the fields "firstname" & "lastname" are
correctly updated. However, the field "student" is still null. Do you
know Why?

Thank you very much

-- 
You received this message because you are subscribed to the Google Groups 
"Google App Engine" group.
To post to this group, send email to google-appengine@googlegroups.com.
To unsubscribe from this group, send email to 
google-appengine+unsubscr...@googlegroups.com.
For more options, visit this group at 
http://groups.google.com/group/google-appengine?hl=en.