[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3102) Cascading ManyToOne collections do not eagerly set identifiers on saveOrUpdate()

[Gail Badner (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=44383#comment-44383 ] 

Gail Badner commented on HHH-3102:
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This is expected behavior. Calling Session.saveOrUpdate( entity ) on an entity already associated with the session does nothing.

> Cascading ManyToOne collections do not eagerly set identifiers on saveOrUpdate()
> --------------------------------------------------------------------------------
>
>                 Key: HHH-3102
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3102
>             Project: Hibernate Core
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.2.4.sp1
>            Reporter: Paul Cowan
>            Priority: Minor
>         Attachments: HibernateKeyPoolTest.java
>
>
> Hi all,
> Not 100% sure if you'd call this a 'bug' as I'm not sure if the correct behaviour is actually specified anywhere. It's certainly oddly inconsistent though.
> Please find attached a standalone test case (requires HSQLDB on the classpath; amend setUp() if you need to use something else) which models a parent-child mapping between 'Mouth' (1) and 'Teeth' (many). The Mouth -> Teeth relationship is bidirectional, with CascadeType.ALL on the single-valued end. Both Mouth and Tooth use a @GenericGenerator, which simply allocates integers from a static keypool.
> A mouth with one tooth is created, saveOrUpdate()d, session is flushed, a new tooth is added, mouth is saveOrUpdate()d again, and session is again flushed. The debug output is as follows:
> *** After creation
> Mouth (id=null) has teeth [canine(id=null)]
> *** Save
> Mouth (id=1) has teeth [canine(id=2)]
> *** Flush
> Hibernate: insert into Mouth (id) values (?)
> Hibernate: insert into Tooth (mouthId, name, id) values (?, ?, ?)
> Mouth (id=1) has teeth [canine(id=2)]
> *** Add new
> Mouth (id=1) has teeth [canine(id=2), molar(id=null)]
> *** Save again
> Mouth (id=1) has teeth [canine(id=2), molar(id=null)]
> *** Flush again
> Hibernate: insert into Tooth (mouthId, name, id) values (?, ?, ?)
> Mouth (id=1) has teeth [canine(id=2), molar(id=3)]
> As you can see, when initially created the IDs for the mouth and tooth are both null (obviously correct). The saveOrUpdate() on the Mouth object then generates identifier values, even though no DB write has been done yet (the .flush()). So far, so good.
> However, when a NEW transient Tooth instance ("molar") is added to the Mouth, and saveOrUpdate() is called once more, the id generator is not invoked, UNTIL such time as the session is flushed. 
> While I guess it's fine  for an object in the 'persistent' state not to actually have an identifier until flush-time (e.g. when using DB-side IDENTITY-type generation), it just seems inconsistent that with a @GenericGenerator the behaviour would vary depending on whether the PARENT object was already persistent or not.
> There are some obvious workarounds (e.g. flush the session upon saving, or save the child entity first independently) but I thought I'd clarify if this behaviour is by design or not and suggest that this be made consistent.

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