OpenJPA + DB2 + WebSphere

Hi, I'm working on my school project where I need to create SessionBeans Entity Classes corresponding to database which is in this case DB2. Right now I'm living my worst programming nightmare, because I have been trying to figure out how to persist simple Entity with single attribute (generated ID), with no effect for 5 days. I'm able to persist Entity with two or more attributes, but I can't crack this one. After persist of following Entity I'm getting as it's ID null instead of generated value from DB2. Can somebody help me please? Thx

Entity class:

Code:

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package entity;

import java.io.Serializable;
import javax.persistence.*;

@Entity
@Table(name = "BINDING")
public class Binding implements Serializable {
        private static final long serialVersionUID = 1L;
        private Long bindingId;

        public Binding() {
        }

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        @Column(name = "BINDING_ID", unique = true, nullable = false)
        public Long getBindingId() {
                return this.bindingId;
        }

        public void setBindingId(Long bindingId) {
                this.bindingId = bindingId;
        }       
}

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persistence.xml:

Code:

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<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
        xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
        <persistence-unit name="AppEJB" transaction-type="JTA">
<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
                <jta-data-source>jdbc/datasource</jta-data-source>
                <class>entity.Binding</class>
                <properties>                       
                        <property name="openjpa.jdbc.Schema" value="BOOKSTORE" />
                        <property name="openjpa.jdbc.DBDictionary" value="db2" />
                </properties>
        </persistence-unit>
</persistence>

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Manage for entity:

Code:

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package manager;

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import entity.Binding;

@Stateless(name = "bookManager", mappedName = "bookManager")
public class BookManager implements BookManagerRemote {
        @PersistenceContext(unitName = "AppEJB")
        private EntityManager em;

        protected EntityManager getEntityManager() {
                return em;
        }

        public BookManager() {
        }

        @Override
        public Binding create(Binding binding) {
                em.persist(binding);
                return binding;
        }
}

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I think the problem is that this generates SQL:

Code:

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INSERT INTO Binding VALUES ()

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instead of

Code:

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INSERT INTO Binding VALUES (DEFAULT)

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