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From "Simon Kitching (JIRA)" <...@myfaces.apache.org>
Subject [jira] Created: (ORCHESTRA-12) Could not generate CGLIB subclass of class [class $Proxy0]
Date Wed, 05 Dec 2007 09:03:43 GMT
Could not generate CGLIB subclass of class [class $Proxy0]
----------------------------------------------------------

                 Key: ORCHESTRA-12
                 URL: https://issues.apache.org/jira/browse/ORCHESTRA-12
             Project: MyFaces Orchestra
          Issue Type: Bug
          Components: Conversation
    Affects Versions: 1.0
            Reporter: Simon Kitching
            Assignee: Simon Kitching
             Fix For: 1.1


Orchestra generates a proxy for every orchestra-scoped bean in order to apply CurrentConversationAdvice,
plus any other advices configured for the conversation. But this fails if something else has
already proxied the bean using java.lang.reflect.Proxy, as that generates a final class that
cglib cannot subclass.

This only happens in the following circumstances:
* aop:scoped-proxy is not being used,
* the bean has one or more spring advices on it (eg it has the @Transactional annotation on
a method in the class), and
* the bean implements one or more interfaces.

The workaround for orchestra-1.0 users is just to attach aop:scoped-proxy to the bean definition.

The cause of the problem is that there can be the following chain of objects:
(1) the real bean
(2) a spring-generated proxy to hold advices to support things like transactional support.
(3) the orchestra-generated proxy to hold CurrentConversationAdvice and others
(4) the scoped proxy object

If (2) is created using java.lang.reflect.Proxy then (3) fails., because cglib tries to subclass
the concrete type of (2), but that is a final type.

Object (2) only exists if there are advices that spring needs to attach. If there are none,
then there is no problem as (3) proxies (1) directly.
Object (2) is always a CGLIB proxy if (4) is an aop:scoped-proxy object, as in that case the
spring code that handles that pokes a magic value into the bean-definition for (1) that forces
cglib to be used.
Object (2) is always a CGLIB proxy if bean (1) implements no interfaces.

But otherwise the problem occurs, and an exception occurs. Unfortunately it is quite common
for a bean to implement interfaces and also have @Transactional, so this does occur frequently.
For orchestra-1.0, using aop:scoped-proxy is recommended, though, so this isn't critical.

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