Re: [Springframework-developer] Intercepting a Prototype Bean

[Rod J. <rod...@in...>]

Mark,

> Is it possible to apply an interceptor to a prototype bean?
Yes.

> The prototype is stateful - i.e one per user
Yes, Spring supports mixins, ie one interceptor per mixin instance.

> I have defined the following in applicationContext.xml
>
>
> <bean id="TestTarget" class="test.MyTarget" singleton="false">
> </bean>
>
>
> <bean id="TestInterceptor"
>
class="org.springframework.transaction.interceptor.TransactionProxyFactoryBe
> an" singleton="false">
> <property name="transactionManager"><ref
> local="transactionManager"/></property>
>
> <property name="target"><ref local="TestTarget"/></property>
>
>
> <property name="transactionAttributes">
> <props>
> <prop key="foo">PROPAGATION_REQUIRED</prop>
> </props>
> </property>
> </bean>
>
>
>
> When I invoke the method foo I get a ClassCastException

Not sure why this is happening but you may need to create the interceptor
chain manually to use a prototype, as TransactionProxyFactoryBean propably
assumes it's dealing with a singleton. So you need to create a chain that
includes:
- the name of your prototype
- the interceptor names, which may be singletons or prototypes as you
require. Use a prototype for mixin support.

The following example comes from the test suite, with minor changes to make
it more obvious:


<bean id="prototypeTarget"
class="org.springframework.aop.interceptor.SideEffectBean"
 singleton="false">
 <property name="count"><value>10</value></property>
</bean>

<!-- This can be a singleton or a prototype (for mixin behaviour) -->
<bean id="debugInterceptor"
class="org.springframework.aop.interceptor.DebugInterceptor">
</bean>


<bean id="prototype"
 class="org.springframework.aop.framework.ProxyFactoryBean">
 <!-- will automatically create invoker interceptor for the prototype -->
 <property
name="interceptorNames"><value>debugInterceptor,prototypeTarget</value></pro
perty>

<!-- Note this -->
 <property name="singleton"><value>false</value></property>
</bean>

There is a bug in M2 to do with prototype AOP handling, which is fixed in
the forthcoming M3. However I don't think it should affect you in such a
simple usage.


Regards,
Rod