I am working on a project for college that uses GWT, Hibernate and Gilead. Basically for the moment users should be able to add friends and remove them. Also, a user can see if his or her friends are online or not.
My trouble is that when I add a friend that is already related to another friend, I get this error:
org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.example.client.YFUser#4]
This is my service class for my gwt application:
public class TestServiceImpl extends PersistentRemoteService implements TestService {
My trouble is here with my implementation class of my service in this method, which is called when a user presses the add friend button on the client-side.
public void addYFUserFriend(String userName){
//this retrieves the current user
YFUser user = (YFUser)getSession().getAttribute(SESSION_USER);
Session session = com.example.server.HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
YFUser friend = (YFUser) session.createQuery("select u FROM YFUser u where u.username = :username").setParameter("username", userName).uniqueResult();
System.out.println("user " + friend.getUsername() + " Found");
user.getFriends().add(friend);
friend.getBefriended().add(user);
session.update(user);
session.update(friend);
session.getTransaction().commit();
}
A scenario:
user1 adds user2 as a friend. This works fine, Then user3 adds user2 and the exception is thrown.
Any ideas why and where my logic is going wrong?
Update: Ok, so I have changed my code, and I have removed all the getCurrentASession() calls and replaced with openSession() calls which are closed at the appropriate point, now the error I am getting is:
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract void com.example.client.TestService.addYFUserFriend(java.lang.String)' threw an unexpected exception: org.hibernate.NonUniqueResultException: query did not return a unique result: 3
It looks to me like you have 3 users with the same user name. As you are using uniqueResult(), you are telling Hibernate that you are expecting only a single value.
Check your database or replace uniqueResult() with List() to see what you get back.