@IdClass cause identifier of an instance altered in em.find

tjunussov · **Posted:** Thu Sep 10, 2009 6:37 pm

This is probably a bug!
When i am trying to find my already persisted Entity (Membership with Composite Id ( @IdClass ))
after when my transaction commited it cause

Code:

4:00:20,593 WARN  [arjLoggerI18N] [com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator_2] TwoPhaseCoordinator.beforeCompletion - failed for com.arjuna.ats.internal.jta.resources.arjunacore.SynchronizationImple@1f5e42b
javax.persistence.PersistenceException: org.hibernate.HibernateException: identifier of an instance of kz.bee.wx.security.Membership was altered from kz.bee.wx.security.MembershipPk@1a532c to kz.bee.wx.security.MembershipPk@8a7ac2b
   at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:629)

i assume what after calling method em.find() it associates my MembershipPk with found Entity and at sync state it replaces with new MembershipPk.

Here is my sample code

Code:

User u=new User("myuser");
Role r=new Role("myrole");
Group g=new Group("mygroup");
            
Membership m = new Membership();
m.setUser(u);
m.setRole(r);
m.setGroup(g);
            
MembershipPk mk = new MembershipPk();
mk.setUser(u);
mk.setRole(r);
mk.setGroup(g);

System.out.println(em.find(m.getClass(), mk));

and my entity is

Code:

package kz.bee.wx.security;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.persistence.Transient;

@Entity
@Table(name = "WX_MEMBERSHIP")
@IdClass(MembershipPk.class)
public class Membership {

   private User user;
   private Role role;
   private Group group;
   private boolean enabled;
   
   @Id
   @ManyToOne
   @JoinColumn(name = "USER_NAME_")
   public User getUser() {
      return user;
   }

   public void setUser(User user) {
      this.user = user;
   }

   @Id
   @ManyToOne
   @JoinColumn(name = "ROLE_NAME_")
   public Role getRole() {
      return role;
   }

   public void setRole(Role role) {
      this.role = role;
   }

   @Id
   @ManyToOne
   @JoinColumn(name = "GROUP_NAME_")
   public Group getGroup() {
      return group;
   }

   public void setGroup(Group group) {
      this.group = group;
   }

   @Column(name = "ENABLED_")
   public boolean isEnabled() {
      return enabled;
   }

   public void setEnabled(boolean enabled) {
      this.enabled = enabled;
   }

   @Transient
   public boolean isActive() {
      return this.isEnabled() && this.getRole().isEnabled() && this.getGroup().isEnabled();
   }
   
   @Override
   public String toString() {
      return user+":"+role+":"+group;
   }
   
   @Override
    public boolean equals(Object arg0) {
        if (arg0 == this) {
            return true;
        }
        else if (arg0 instanceof Membership) {
            return user.getName().equals(((Membership)arg0).user.getName()) &&
            role.getName().equals(((Membership)arg0).role.getName()) &&
            group.getName().equals(((Membership)arg0).group.getName());
        }
        return false;
    }

   @Override
    public int hashCode() {
        return user.hashCode() ^ role.hashCode() ^ group.hashCode();
    }
}

and primary key

Code:

package kz.bee.wx.security;

import java.io.Serializable;

import javax.persistence.Embeddable;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Embeddable
public class MembershipPk implements Serializable {

   /**
    * 
    */
   private static final long serialVersionUID = 1L;
   
   private User user;
   private Role role;
   private Group group;
   

   @ManyToOne
   @JoinColumn(name = "USER_NAME_")
   public User getUser() {
      return user;
   }

   public void setUser(User user) {
      this.user = user;
   }

   @ManyToOne
   @JoinColumn(name = "ROLE_NAME_")
   public Role getRole() {
      return role;
   }

   public void setRole(Role role) {
      this.role = role;
   }

   @ManyToOne
   @JoinColumn(name = "GROUP_NAME_")
   public Group getGroup() {
      return group;
   }

   public void setGroup(Group group) {
      this.group = group;
   }
   
   @Override
    public boolean equals(Object arg0) {
        if (arg0 == this) {
            return true;
        }
        else if (arg0 instanceof MembershipPk) {
            return user.getName().equals(((MembershipPk)arg0).user.getName()) &&
            role.getName().equals(((MembershipPk)arg0).role.getName()) &&
            group.getName().equals(((MembershipPk)arg0).group.getName());
        }
        return false;
    }

    @Override
    public int hashCode() {
       return user.hashCode() ^ role.hashCode() ^ group.hashCode();
    }
}

p.s User, Role and Group are simple classes with name as @Id

dmarcosm · **Posted:** Thu Sep 17, 2009 5:10 pm

I have exactly the same error in my application.

How do you solve this? Has anyone any idea about solving this issue?

Thanks in advance!

tjunussov · **Posted:** Thu Sep 17, 2009 5:26 pm

hi! while i didn't get reply from hibernate guys,
i wrote own EntityIdentifier, it uses em.createQuery instead of em.find

maybe it looks ugly :(, but it works!

code smth like this,

Code:

String criteria = "FROM " + getClazz().getName() + " WHERE ";

            for (String field : identifierFields) {
               criteria += field + "=:" + field + " AND ";
            }

            criteria = criteria.substring(0, criteria.length() - 4);
            
            Query query = entityManager.createQuery(criteria);

            for (String field : identifierFields) {
               Method getter = Reflections.getGetterMethod(identifierIdClass, field);
               Object value = Reflections.invoke(getter, identifier);
               query.setParameter(field, value);
            }

            return query.getSingleResult();

i hope hibernate guys look into this problem in near future :)

dmarcosm · **Posted:** Thu Sep 17, 2009 5:35 pm

Thank for your reply. I'll test your "workaround". =]

I hope it too. It's too weird that hibernate do not support this.

Another solutions would be welcome.

Thanks.

tair.sabirgaliev · **Joined:** Fri Sep 18, 2009 12:43 am **Posts:** 1

The two "equal" MembershipPk's have different hashCodes (hex-number behind @ symbol) as shown in your stack trace:

Quote:

kz.bee.wx.security.MembershipPk@1a532c to kz.bee.wx.security.MembershipPk@8a7ac2b

so I suspect that MembershipPk.hashCode() is not implemented correctly :)
Perhaps it should be something like this:

Code:

   @Override
    public int hashCode() {
       return user.getName().hashCode() ^ role.getName().hashCode() ^ group.getName().hashCode();
    }

Any other ideas?

tjunussov · **Posted:** Fri Sep 18, 2009 4:16 am

it doesnt matter, i've tried it!
hibernate generates forcely new instance,
i spend whole day trying to solve it :(

dmarcosm · **Posted:** Fri Sep 18, 2009 4:03 pm

I've tried implementing both hashCode and equals methods, but it doesn't work.

Code:

identifier of an instance of Test was altered from TestPK@1 to TestPK@1

Even with the same hashCode the error persist.

dmarcosm · **Posted:** Fri Sep 18, 2009 5:07 pm

I've got the solution! (Maybe =])

In my case, I had to implement the "equals" method into the associated class. That is, if you have an A class that is associated with a B class that has a composite id, you must implement the "equals" method in the A class, and it works.

I hope it help someone.

See ya.

sureshvayugundla · **Joined:** Mon Aug 09, 2010 4:56 pm **Posts:** 4

It worked for me by implementing the hashCode() & equals() method.

Thank you all for supporting. I spent whole lot of time figuring out myself, finally I am glad found the solution here.

Thanks again.

sureshvayugundla · **Joined:** Mon Aug 09, 2010 4:56 pm **Posts:** 4

I am again running into the same problem. I thought it worked and posted the reply on to this thread. Here is the scenario:

I am creating a web application where author performs add/modify/delete on books. (Struts2 - Hibernate)
Example: Author - Books
1. When author goes on edit mode, he can see all of his books under children. When author adds some books and deletes one book and then save works perfectly fine.
2. If he does the same steps again for 2nd time from the same web page, I am getting the below error.

Exception in saveOrUpdateObject()... org.hibernate.HibernateException: identifier of an instance of Book was altered from 37 to 119.

Does any one has ideas?

Thanks,