package com.foo.persist;

import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Version;

@Entity
@Table(name="RPR_ROOT_PARENT")
public class RootParent {
   
   private Long internalId;
   
   private String rootParentId;
   
   private Integer version;
   
   private Set<Association> associationSet;
   
   @OneToMany(mappedBy="rootParent", cascade={CascadeType.PERSIST, CascadeType.MERGE})
   public Set<Association> getAssociationSet() {
      return associationSet;
   }

   public void setAssociationSet(Set<Association> associationSet) {
      this.associationSet = associationSet;
   }

   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   @Column(name="RPR_UID")
   public Long getInternalId() {
      return internalId;
   }

   public void setInternalId(Long internalId) {
      this.internalId = internalId;
   }

   @Column(name="RPR_ID")
   public String getRootParentId() {
      return rootParentId;
   }

   public void setRootParentId(String rootParentId) {
      this.rootParentId = rootParentId;
   }

   @Version
   @Column(name="RPR_VERSION")
   public Integer getVersion() {
      return version;
   }

   public void setVersion(Integer version) {
      this.version = version;
   }

   @Override
   public int hashCode() {
      final int PRIME = 31;
      int result = 1;
      result = PRIME * result + ((rootParentId == null) ? 0 : rootParentId.hashCode());
      return result;
   }

   @Override
   public boolean equals(Object obj) {
      if (this == obj)
         return true;
      if (obj == null)
         return false;
      if (getClass() != obj.getClass())
         return false;
      final RootParent other = (RootParent) obj;
      if (rootParentId == null) {
         if (other.rootParentId != null)
            return false;
      } else if (!rootParentId.equals(other.rootParentId))
         return false;
      return true;
   }
}

package com.foo.persist;

import java.io.Serializable;

import javax.persistence.CascadeType;
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.Version;

@Entity
@IdClass(AssociationPK.class)
@Table(name="ASC_ASSOCIATION")
public class Association implements Serializable {
   
   /**
    *
    */
   private static final long serialVersionUID = -3746181614360357763L;
   
   private long rootParentUid;
   
   private RootParent rootParent;
   
   private long leafParentUid;
   
   private LeafParent leafParent;
   
   private Integer version;
   
   @Id
   @Column(name="ASC_LPR_UID", updatable=false, insertable=false)
   public long getLeafParentUid() {
      return leafParentUid;
   }

   public void setLeafParentUid(long leafParentUid) {
      this.leafParentUid = leafParentUid;
   }

   @Id
   @Column(name="ASC_RPR_UID", updatable=false, insertable=false)
   public long getRootParentUid() {
      return rootParentUid;
   }

   public void setRootParentUid(long rootParentUid) {
      this.rootParentUid = rootParentUid;
   }
   
   @ManyToOne(cascade={CascadeType.PERSIST, CascadeType.MERGE})
   @JoinColumn(name="ASC_LPR_UID")
   public LeafParent getLeafParent() {
      return leafParent;
   }

   public void setLeafParent(LeafParent leafParent) {
      this.leafParent = leafParent;
   }

   @ManyToOne(cascade={CascadeType.PERSIST, CascadeType.MERGE})
   @JoinColumn(name="ASC_RPR_UID")
   public RootParent getRootParent() {
      return rootParent;
   }

   public void setRootParent(RootParent rootParent) {
      this.rootParent = rootParent;
   }
   
   @Version
   @Column(name="ASC_VERSION")
   public Integer getVersion() {
      return version;
   }

   public void setVersion(Integer version) {
      this.version = version;
   }

   @Override
   public int hashCode() {
      final int PRIME = 31;
      int result = 1;
      result = PRIME * result + ((leafParent == null) ? 0 : leafParent.hashCode());
      result = PRIME * result + ((rootParent == null) ? 0 : rootParent.hashCode());
      return result;
   }

   @Override
   public boolean equals(Object obj) {
      if (this == obj)
         return true;
      if (obj == null)
         return false;
      if (getClass() != obj.getClass())
         return false;
      final Association other = (Association) obj;
      if (leafParent == null) {
         if (other.leafParent != null)
            return false;
      } else if (!leafParent.equals(other.leafParent))
         return false;
      if (rootParent == null) {
         if (other.rootParent != null)
            return false;
      } else if (!rootParent.equals(other.rootParent))
         return false;
      return true;
   }

   
}

package com.foo.persist;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Id;

@SuppressWarnings("unused")
public class AssociationPK implements Serializable {

   /**
    *
    */
   private static final long serialVersionUID = 1L;

   private long leafParentUid;
   
   private long rootParentUid;
   
   public AssociationPK() {}
   
   public AssociationPK(long leafParentUid, long rootParentUid) {
      this.leafParentUid = leafParentUid;
      this.rootParentUid = rootParentUid;
   }

   public long getLeafParentUid() {
      return leafParentUid;
   }

   public void setLeafParentUid(long leafParentUid) {
      this.leafParentUid = leafParentUid;
   }

   public long getRootParentUid() {
      return rootParentUid;
   }

   public void setRootParentUid(long rootParentUid) {
      this.rootParentUid = rootParentUid;
   }
}

package com.foo.persist;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Version;

@Entity
@Table(name="LPR_LEAF_PARENT")
public class LeafParent {
   
   private Long internalId;
   
   private String leafParentId;
   
   private Integer version;
   
   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   @Column(name="LPR_UID")
   public Long getInternalId() {
      return internalId;
   }

   public void setInternalId(Long internalId) {
      this.internalId = internalId;
   }

   @Column(name="LPR_ID")
   public String getLeafParentId() {
      return leafParentId;
   }

   public void setLeafParentId(String leafParentId) {
      this.leafParentId = leafParentId;
   }

   @Version
   @Column(name="LPR_VERSION")
   public Integer getVersion() {
      return version;
   }

   public void setVersion(Integer version) {
      this.version = version;
   }

   @Override
   public int hashCode() {
      final int PRIME = 31;
      int result = 1;
      result = PRIME * result + ((leafParentId == null) ? 0 : leafParentId.hashCode());
      return result;
   }

   @Override
   public boolean equals(Object obj) {
      if (this == obj)
         return true;
      if (obj == null)
         return false;
      if (getClass() != obj.getClass())
         return false;
      final LeafParent other = (LeafParent) obj;
      if (leafParentId == null) {
         if (other.leafParentId != null)
            return false;
      } else if (!leafParentId.equals(other.leafParentId))
         return false;
      return true;
   }

   
}

package com.foo.test;

import java.util.HashSet;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import junit.framework.TestCase;

import com.foo.persist.Association;
import com.foo.persist.LeafParent;
import com.foo.persist.RootParent;

public class JpaTest extends TestCase {
   
   private static EntityManagerFactory emf;
    private static EntityManager em;
   
    private static boolean init = false;
   
    @Override
   protected void setUp() throws Exception {
       if (!init) {
          // Create EntityManagerFactory for persistent unit named "pu1"
            // to be used in this test
            emf = Persistence.createEntityManagerFactory("pu1");
           
            // Create a new EntityManager
            em = emf.createEntityManager();
           
            init = true;
       }
   }

    private void doMerge(Object pObj) {
      em.getTransaction().begin();
      em.merge(pObj);
      em.getTransaction().commit();
   }
   
    private void doPersist(Object pObj) {
       em.getTransaction().begin();
       em.persist(pObj);
       em.getTransaction().commit();
    }
   
    public void testUpdateRootParentWithTransientLeafParent() throws Exception {
      Query q = em.createQuery("select r from RootParent r where r.rootParentId = 'RPR1'");
      RootParent r = (RootParent)q.getSingleResult();
      LeafParent l = new LeafParent();
      l.setLeafParentId("TRANSIENTLEAF");
      Association a = new Association();
      a.setLeafParent(l);
      a.setRootParent(r);
      r.getAssociationSet().add(a);
      doMerge(r);
    }
}

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
   version="1.0">
   <persistence-unit name="pu1">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>
      <class>com.foo.persist.Association</class>
      <class>com.foo.persist.AssociationPK</class>
      <class>com.foo.persist.LeafParent</class>
      <class>com.foo.persist.RootParent</class>
      <properties>
      
         <property name="hibernate.hbm2ddl.auto" value="create" />
         <property name="hibernate.dialect"
            value="org.hibernate.dialect.DerbyDialect" />
         <property name="hibernate.connection.driver_class"
            value="org.apache.derby.jdbc.EmbeddedDriver" />
         <property name="hibernate.connection.username" value="" />
         <property name="hibernate.connection.password" value="" />
         <property name="hibernate.connection.url"
            value="jdbc:derby:data\testdb;create=true" />
         <property name="hibernate.max_fetch_depth" value="3" />
         <property name="hibernate.show_sql" value="false" />
         
      </properties>
   </persistence-unit>
</persistence>