Help needed with Roo Polymorphism

[BlakkPhoenixx]

Dear Sirs et Madames,
I am creating an application which has polymorphism in its design. I have a class PersistentEntity, and another class called Attribute (abstract), and classes DateAttribute,StringAttribute and NumberAttribute which all are subclasses of Attribute.

A PersistentEntity object has a set of Attributes:

package com.testing.genericappcreator.domain;

import java.util.HashSet;
import java.util.Set;

import org.springframework.roo.addon.entity.RooEntity;
import org.springframework.roo.addon.javabean.RooJavaBean;
import org.springframework.roo.addon.tostring.RooToString;

import javax.persistence.CascadeType;
import javax.persistence.ManyToMany;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

@RooJavaBean
@RooToString
@RooEntity
public class PersistentEntity {

    @NotNull
    private String entityName;

    @NotNull
    @Size(max = 255)
    private String entityDescription;
    
    @ManyToMany(cascade = CascadeType.ALL)
    private Set<com.testing.genericappcreator.domain.Attribute> attributes = new HashSet<com.testing.genericappcreator.domain.Attribute>();
} 

Now when I create a web tier

controller all ~.web 

in roo, I can navigate to relevant page in application and create a few NumberAttribute and DateAttribute objects, etc. However when I got to the create PersistentEntity page, in the field for Attributes is the message "No attributes found"...why is it not finding the subclass objects of Attribute, does hibernate not support polymorphic queries?

Could anyone please advise?

Thanks in advance...