RE: [Springframework-developer] Intercepting a Prototype Bean

[MacMahon, M. <M.M...@em...>]

Hi Rod, all,

Thanks very much for the prompt and detailed replies.

I have tried to apply your suggested solution to my problem but am still
encountering the same issues
I.E the same TestTarget instance is being re-used for each invocation!

Have I misunderstood?

I have defined the following in applicationContext.xml


<!-- TestTarget implements the ITestTarget interface - one method foo() -->
<bean id="TestTarget" class="test.TestTarget" singleton="false">    
</bean>	

<!-- Transaction Interceptor Chain-->

<!-- Specified as a prototype (for mixin behaviour) -->
<bean id="MixinTransactionInterceptor"
class="org.springframework.transaction.interceptor.TransactionInterceptor"
singleton="false">
	<property name="transactionManager"><ref
local="transactionManager"/></property>	
	<property name="transactionAttributeSource">
        <value>test.ITestTarget.foo=PROPAGATION_REQUIRED</value>
    </property>
</bean>


<!--Applies MixinTransactionInterceptor to TestTarget -->
<bean id="TestInterceptor"
class="org.springframework.aop.framework.ProxyFactoryBean" singleton="true">
	 <property
name="interceptorNames"><value>MixinTransactionInterceptor,TestTarget</value
></property>
	 <property name="singleton"><value>false</value></property>
</bean>



My test is as simple as it can get ;-)

public class TestTarget implements ITestTarget
{	
 private int invocationCount = 0;
    
 public void foo()
 {
 	System.err.println
	(
		"<<TestTarget:foo>> "+toString()+" Invocation Count is
"+(++invocationCount)
	);
 }
}

ITestTarget testInterceptor1 =
(ITestTarget)context.getBean("TestInterceptor");
ITestTarget testInterceptor2 =
(ITestTarget)context.getBean("TestInterceptor");			
testInterceptor1.foo();
testInterceptor2.foo();

Output is 

[java] <<TestTarget:foo>> test.TestTarget@e183e9 Invocation Count is 1
[java] <<TestTarget:foo>> test.TestTarget@e183e9 Invocation Count is 2



On a related note, I think it would be _nice_ to be able to define the
transaction behaviour in the same manner 
adopted by TransactionProxyFactoryBean.

Also, is it possible to apply my MixinTransactionInterceptor to multiple
target classes

	<property name="transactionAttributeSource">
        <value>
		test.ITestTarget.foo=PROPAGATION_REQUIRED		
		test.IOtherObject.bar=PROPAGATION_REQUIRED	  
		</value>
    </property>



Thanks again,

Mark

-----Original Message-----
From: Rod Johnson [mailto:rod...@in...]
Sent: 20 November 2003 17:29
To: spr...@li...
Subject: Re: [Springframework-developer] Intercepting a Prototype Bean


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




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