[hibernate-issues] [Hibernate-JIRA] Updated: (HHH-2352) ClassCastException in Session.get()

[Gail Badner (JIRA)]

     [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2352?page=all ]

Gail Badner updated HHH-2352:
-----------------------------

    Attachment: testcase.tgz

I have attached a test case that reproduces this and several related issues.

In particular, it reproduces the following:

1) When using Session.load() to load an Item object with an ID that is the same as a Client object that is already in the current session, the Client object is returned. When Session.get() is used, null is (correctly) returned. The behavior is the same with and without using a second-level cache.

2) When using Session.get() to load an Item object with an ID that is the same as a Client object that was cached in a second-level cache in a previous session, the Client object is returned. A check using instanceof before assigning the returned object to an Item variable can be used to avert a ClassCastException.

3) When using Session.load() to load an Item object with an ID that is the same as a Client object that was cached in a second-level cache in a previous session, an Item proxy is returned. A ClassCastException is thrown when the proxy is initialized, since it is (incorrectly) a Client object. Checking the return value before initializing the proxy does not help since the the proxy is of type Item.

As mentioned earlier, using a Criteria or HQL query is a good workaround for this issue.

Gail Badner
SourceLabs - http://www.sourcelabs.com
Dependable Open Source Systems 

> ClassCastException in Session.get()
> -----------------------------------
>
>          Key: HHH-2352
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2352
>      Project: Hibernate3
>         Type: Bug

>   Components: core
>     Versions: 3.2.1
>  Environment: Hibernate 3.2.1
>     Reporter: Alexey Romanchuk
>     Priority: Critical
>  Attachments: testcase.tgz
>
>
> We have inheritance with joined-subclass mapping. Imagine that we have parent class - BaseObject and two subclasses - Client and Item. We enable second level cache on BaseObject. 
> try to load Client in first session 
> Client client = ( Client ) s1.get( Client.class, 1851727l );
> after this we have this client in second level cache.
> Next - load another subclass with same id:
> Item item = ( Item ) s2.get( Item.class, 1851727l );
> and here we have ClassCastException because hibernate found BaseObject (Client) and return it instead of null.
> The solution is class check in org.hibernate.event.def.DefaultLoadEventListener.loadFromSecondLevelCache() function. This is crititcal bug that violates Session API.

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