Spring Transaction - Proxy confusion

Question

 <tx:advice id="txAdvice" transaction-manager="jtaTxManager">
  <tx:attributes>
   <tx:method name="*" />
  </tx:attributes>
 </tx:advice>

 <aop:config proxy-target-class="true">
  <aop:pointcut id="fooServiceOperation"
   expression="execution(* x.y.SampClass.save(..))" />
  <aop:advisor advice-ref="txAdvice" pointcut-ref="fooServiceOperation" />
 </aop:config>

 <bean id="Samp1" class=" x.y.SampClass"></bean>

        <bean id="SearchDispatchRpcGwtServlet" class="x.y.server.SearchDispatchRpcGwtServlet">
  <constructor-arg>
       <list>
         <ref bean="webServiceClient"/>                          
       </list>
  </constructor-arg>      
 </bean>

 <!-- Service Clients --> 
 <bean id="webServiceClient" class="x.y.KSBClientProxyFactoryBean">
  <property name="serviceEndpointInterface" value="x.y.service.WebService" />
  <property name="serviceQName" value="{http://x.y.org/wsdl/organization}WebService" />
 </bean>

This is the part of sample spring context file. I am trying to create a transaction advice for SampClass to execute on the save method.

So from my understanding it should create a proxy for SampClass only.

I have a SearchDispatchRpcGwtServlet which takes as an argument a webservice Client which is also a proxy in itself. This bean is also getting proxied for some reason where it fails because it cannot create a proxy of a proxy.

I must add that SearchDispatchRpcGwtServlet creates an instance of SampClass and calls the save method.

I get the following exception:

java.lang.IllegalArgumentException: Cannot subclass final class class $Proxy118 at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer .java:446) at net.sf.cglib.transform.TransformingClassGenerator. generateClass(TransformingClassGenerator.java:33)

I dont understand why SearchDispatchRpcGwtServlet proxy is getting created. Can someone explain.

Addition Stack Trace

Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class $Proxy117]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Cannot subclass final class class $Proxy117
    at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:213)
    at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:110)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.createProxy(AbstractAutoProxyCreator.java:473)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:348)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:309)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:361)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.postProcessObjectFromFactoryBean(AbstractAutowireCapableBeanFactory.java:1427)
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport$1.run(FactoryBeanRegistrySupport.java:139)
    ... 85 more
Caused by: java.lang.IllegalArgumentException: Cannot subclass final class class $Proxy117
    at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer.java:446)
    at net.sf.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33)
    at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
    at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216)
    at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
    at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:285)
    at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:201)