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Item - Bid with a successfulBid association

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hbf

Post subject: Item - Bid with a successfulBid association

Posted: Wed Jun 10, 2009 10:11 am

Newbie

Joined: Wed Feb 25, 2009 8:48 am
Posts: 5

Hi,

I am trying to get the example from "Java Persistence with Hibernate" (2007 edition) to run: an Item can have zero, one, or more Bids and it can have a successfulBid.

Here's my approach:

Code:

package org.hbf.basics.hibernate;

import java.util.ArrayList;
import java.util.Collection;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.testng.AbstractTestNGSpringContextTests;
import org.testng.annotations.Test;

@ContextConfiguration
public class HibernateTest extends AbstractTestNGSpringContextTests
{
  @Test()
  public void bidsTest()
  {
    SessionFactory sessionFactory = (SessionFactory) applicationContext.getBean("sessionFactory");
    Session session = sessionFactory.openSession();
    Transaction transaction = session.beginTransaction();

    Item item = new Item();
    Bid bid = new Bid();

    bid.setItem(item);
    item.getBids().add(bid);
    item.setSuccessfulBid(bid);

    session.save(item);
    session.save(bid);

    transaction.commit();
    session.close();
  }

  @Entity
  public static class Item
  {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @OneToMany(mappedBy = "item")
    private final Collection<Bid> bids = new ArrayList<Bid>();

    @OneToOne(optional = true)
    @JoinColumn(unique = true, nullable = true, updatable = false)
    private Bid successfulBid;

    public void setSuccessfulBid(Bid successfulBid)
    {
      this.successfulBid = successfulBid;
    }

    public Collection<Bid> getBids()
    {
      return bids;
    }
  }

  @Entity
  public static class Bid
  {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @ManyToOne()
    @JoinColumn(name = "item", nullable = false)
    private Item item;

    public void setItem(Item item)
    {
      this.item = item;
    }
  }
}

This runs without exceptions but strangely, there the 'successfulBid_id' field contains NULL in the DB even though I call setSuccessfulBid(bid). Any ideas what the problem is?

Thanks a lot,
Hbf

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hbf

Post subject: Re: Item - Bid with a successfulBid association

Posted: Fri Jun 12, 2009 5:55 am

Newbie

Joined: Wed Feb 25, 2009 8:48 am
Posts: 5

I found code for this example (see Item.java and Bid.java) and have isolated the strange behaviour further.

To-0/1 works but To-1 does not
The following mapping in class Item,

Code:

    @OneToMany(mappedBy = "item")
    private final Collection<Bid> bids = new ArrayList<Bid>();

    @ManyToOne
    @JoinColumn(nullable = true)
    private Bid successfulBid;

makes the code work. However, I have a slightly different use case in which there always is and must be a successfulBid. So I set @JoinColumn(nullable = false) in the above. With this, I get an exception

not-null property references a null or transient value: org.hbf.basics.hibernate.HibernateTest$Item.successfulBid

Does anybody know why?

I also get this exception when I set @ManyToOne(optional=false).

Cascading does not work
Secondly, I want to use cascading and enable it on both (class Item):

Code:

    @OneToMany(mappedBy = "item", cascade = {
      CascadeType.ALL
    })
    private final Collection<Bid> bids = new ArrayList<Bid>();

    @ManyToOne(cascade = {
      CascadeType.ALL
    })
    @JoinColumn(nullable = true)
    private Bid successfulBid;

And in bidsTest() I disable the save of the child:

Code:

    session.save(item);
    //session.save(bid);

With this, I get

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: org.hbf.basics.hibernate.HibernateTest$Bid

Any hints much appreciated,
Hbf

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