HashCodeCacheKeyGenerator doesn't make 2 different cache keys on method invocations on 2 different subclasses of same superclass.

HashCodeCacheKeyGenerator creates same CacheKeys for method invocations on different objects if:
1. those objects have a common interface and,
2. those objects invoke the same method, defined in the superinterface and,
3. the make the invocation with equal arguments

I tested this with a piece of code like this:

Dao daoA = (Dao) ctx.getBean("daoA");
Dao daoB = (Dao) ctx.getBean("daoB");

BusObject busA = daoA.loadById(new Integer(0));
BusObject busB = daoB.loadById(new Integer(0));

System.out.println("busA = " + busA.toString());
System.out.println("busB = " + busB.toString());

And the output was:

[java] busA = BusObjectA[id=0]
[java] busB = BusObjectA[id=0]

(Bean "daoB.loadById" produces objects of type BusObjectB)

Cache returned BusObjectA as a cache result for daoBloadById invocation - that is wrong, because daoB.loadById never returns BusObjectA objects

The problem is in the HashCodeCacheKeyGenerator - and i think that using methodInvocation.getThis().getClass() in creating the hashCode would fix this problem (for non-static invocations). For static invocations methodInvocation.getThis() is null - in that cases methodInvocation.getMethod() would probably be suficent.

I'll try to upload the program i used for reproducing the bug (if Jira lets me).