Question

I want to create a thread-local object (with interceptors) using DefaultAdvisorAutoProxyCreator. I know how to do that using ProxyFactoryObject:

<?xml version="1.0" encoding="utf-8"?>
<objects xmlns="http://www.springframework.net">
    <object id="ConsoleLoggingBeforeAdvisor" type="Spring.Aop.Support.DefaultPointcutAdvisor" singleton="false">
        <property name="Advice">
            <object type="Spring.Examples.AopQuickStart.ConsoleLoggingBeforeAdvice"/>
        </property>
    </object>
    <object id="ServiceCommandTargetSource" type="Spring.Aop.Target.ThreadLocalTargetSource">
        <property name="TargetObjectName" value="ServiceCommandTarget"/>
   </object>
    <object id="ServiceCommandTarget" type="Spring.Examples.AopQuickStart.ServiceCommand" singleton="false"/>
    <object name="ServiceCommand" type="Spring.Aop.Framework.ProxyFactoryObject">
        <property name="TargetSource" ref="ServiceCommandTargetSource"/>
        <property name="InterceptorNames">
            <list>
                <value>ConsoleLoggingBeforeAdvisor</value>
            </list>
        </property>
    </object>
</objects>

However, I don’t know how to get the same effect using DefaultAdvisorAopCreator. Here’s what I tried (but didn’t work):

<?xml version="1.0" encoding="utf-8"?>
<objects xmlns="http://www.springframework.net">
    <object id="ConsoleLoggingBeforeAdvisor" type="Spring.Aop.Support.DefaultPointcutAdvisor" singleton="false">
        <property name="Advice">
            <object type="Spring.Examples.AopQuickStart.ConsoleLoggingBeforeAdvice"/>
        </property>
    </object>
    <object id="ServiceCommand" type="Spring.Examples.AopQuickStart.ServiceCommand" singleton="false"/>
    <object type="Spring.Aop.Framework.AutoProxy.DefaultAdvisorAutoProxyCreator">
        <property name="CustomTargetSourceCreators">
            <list element-type="Spring.Aop.Framework.AutoProxy.ITargetSourceCreator">
                <object id="ThreadLocalTargetSourceCreator" type="Spring.Examples.AopQuickStart.ThreadLocalTargetSourceCreator"/>
            </list>
        </property>
    </object>
</objects>

ThreadLocalTargetSourceCreator is a custom class that unconditionally returns a ThreadLocalTargetSource instance:

namespace Spring.Examples.AopQuickStart {
    public class ThreadLocalTargetSourceCreator : AbstractPrototypeTargetSourceCreator {
        protected override AbstractPrototypeTargetSource CreatePrototypeTargetSource(Type objectType, string name, IObjectFactory factory) {
            return new ThreadLocalTargetSource();
        }
    }
}

So, in summary, when I request ServiceCommand from Spring.NET with the first config (using ProxyFactoryObject), I get only one instance of the object per thread (correct behavior). However, with the second config (DefaultAdvisorAutoProxyCreator), I get a new instance every time (incorrect behavior; expecting one instance per thread).

Any thoughts?

Answer 1

Ok, I found out why it was not working as expected. Silly as it seems, I was creating and returning a new instance of ThreadLocalTargetSource from AbstractPrototypeTargetSourceCreator.GetTargetSource(). Of course, each new instance of ThreadLocalTargetSource would have no clue of any existing target instances created by its “cousins” before, so it would create a new instance of its target every time an instance was requested.

The resolution was very simple. I just updated my implementation of ITargetSourceCreator to make sure it created a single instance of ThreadLocalTargetSource and returned that instance each time AbstractPrototypeTargetSourceCreator.GetTargetSource() was called:

namespace Spring.Examples.AopQuickStart {
    public class ThreadLocalTargetSourceCreator : AbstractPrototypeTargetSourceCreator {
        private readonly ThreadLocalTargetSource _threadLocalTargetSource;

        public ThreadLocalTargetSourceCreator() {
            _threadLocalTargetSource = new ThreadLocalTargetSource();
        }

        protected override AbstractPrototypeTargetSource CreatePrototypeTargetSource(Type objectType, string name, IObjectFactory factory) {
            return _threadLocalTargetSource;
        }
    }
}

With this code, it works perfectly for me and I get a thread-local life time for my proxied objects.