How to wire proxy objects in spring?

I am using proxy beans with property-selectable transport protocol. My problem is that bean properties cannot be converted, but I really don't know why. This is the situation:

My property: service.protocol=rmi

<!-- This is the 'multiplexing' factory bean (using this because properties
cannot be used in bean names and aliases -->

   <bean name="dbFormGenWindowComponent" 
  class="org.springframework.beans.factory.config.BeanReferenceFactoryBean">
  <property name="targetBeanName" value="dbFormGenWindowComponent-${service.protocol}invoker" />
 </bean>

<!-- Here are the service invoker beans with two protocols: -->

  <bean name="dbFormGenWindowComponent-rmiinvoker" class="org.springframework.remoting.rmi.RmiProxyFactoryBean">
 <property name="serviceUrl" value="${ringwindow.serviceURL.rmi}/${ringwindow.service.name}-dbFormGenWindowComponent"/>
 <property name="serviceInterface" value="foo.bar.service.formgen.windows.FormGenWindowComponent" />
 <property name="lookupStubOnStartup" value="false"/>
  </bean>

The exception on startup is:

org.springframework.beans.TypeMismatchException: Failed to convert property value of type [$Proxy541] to required type [foo.bar.service.formgen.windows.FormGenWindowComponent] for property 'formGenWindowComponent'; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [$Proxy541] to required type [foo.bar.service.formgen.windows.FormGenWindowComponent] for property 'formGenWindowComponent': no matching editors or conversion strategy found

I think nested factory beans should work fine. Do you have any idea how to get this work?

Solution

This usually happens when you have defined your injection point types to be concrete classes, rather than interfaces, but you are proxying based on interface. For example:

public interface Foo { .. }
public class FooImpl { .. } // this is declared as bean

public class Bar {
    private FooImpl foo; // this fails
    private Foo foo; // correct way
}

In the case of factory beans this may be due to the factory bean's return type being defined as a concrete class. If you can't change anything in the classes, you can configure spring to use cglib-proxying, by:

<aop:scoped-proxy> - inside a bean definition - this will configure proxies of the bean
<aop:aspectj-autoproxy proxy-target-class="true"> - changes this globally