[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2466) cglib proxy doesn't ensure java identity within a session

[Stephen Haberman (JIRA)]

cglib proxy doesn't ensure java identity within a session
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         Key: HHH-2466
         URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2466
     Project: Hibernate3
        Type: Bug

  Components: core  
    Versions: 3.2.2    
    Reporter: Stephen Haberman


Because CGLIBLazyInitializer uses composition instead of inheritance, there are two object instances (one for the proxy, one for the real instance) for the same row in the same session. Documentation section 4.3 says otherwise, but it is wrong.

Example:

fooProxy = ...getFoo() returns a Foo proxy...
bar = fooProxy.makeNewBar()
// makeNewBar() = { bar = new Bar(); bar.setFoo(this); return bar }
fooClean = bar.getFoo()
assert fooProxy == fooClean // fails

When "makeNewBar" does "setFoo" the parameter "this" is the non-proxied Foo instance. We have effectively leaked the non-proxied instance.

CGLIBLazyInitializer:155 contains a cute hack to try to avoid this--if "makeNewBar()" returns the non-proxied Foo instance, it switches out and returns the Foo proxy instead. However, this only solves the trivial case where the instance method returns the instance itself.

Basically this means equals/hashCode have to be implemented all the time because the "hibernate ensures java identity within a session" assertion is wrong.

The best fix seems like changing the cglib proxy to not proxy to a separate instance but to proxy to its parent class. That way when "bar.setFoo(this)" was called, "this" would still be the proxy. And then there really would be "1 instance per database row".



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