Question

Is it possible to create a factory or proxy that can decide if thread is running in (Web)Request or background-process (ie. scheduler) and then depending on that information, it creates a session bean or a prototype bean?

Example (pseudo Spring config 🙂

<bean id="userInfoSession" scope="session" />
<bean id="userInfoStatic" scope="prototype" />

<bean id="currentUserInfoFactory" />

<bean id="someService" class="...">
    <property name="userInfo" ref="currentUserInfoFactory.getCurrentUserInfo()" />
</bean>

I hope this makes my question easier to understand…

---

My Solution

It’s never to late to update own questions ;). I solved it with two different instances of client session, one SessionScoped client session and one SingletonScoped session. Both are normal beans.

<bean id="sessionScopedClientSession" class="com.company.product.session.SessionScopedClientSession" scope="session">
    <aop:scoped-proxy />
</bean>

<bean id="singletonScopedClientSession" class="com.company.product.session.SingletonScopedClientSession" />

<bean id="clientSession" class="com.company.product.session.ClientSession">
    <property name="sessionScopedClientSessionBeanName" value="sessionScopedClientSession" />
    <property name="singletonScopedClientSessionBeanName" value="singletonScopedClientSession" />
</bean>

The ClientSession will then decide if singleton or session scope:

private IClientSession getSessionAwareClientData() {
    String beanName = (isInSessionContext() ? sessionScopedClientSessionBeanName : singletonScopedClientSessionBeanName);
    return (IClientSession) ApplicationContextProvider.getApplicationContext().getBean(beanName);
}

Where session type could be gathered through this:

private boolean isInSessionContext() {
    return RequestContextHolder.getRequestAttributes() != null;
}

All the classes implement a interface called IClientSession. Both singletonScoped and sessionScoped beans extends from a BaseClientSession where the implementation is found.

Every service then can use the client session ie:

@Resource
private ClientSession clientSession;

    ...

public void doSomething() {
    Long orgId = clientSession.getSomethingFromSession();
}

Now if we go one step further we can write something like a Emulator for the session. This could be done by initializing the clientSession (which is in no context of a request) the singleton session. Now all services can use the same clientSession and we still can “emulate” a user ie:

        clientSessionEmulator.startEmulateUser( testUser );
        try {
            service.doSomething();
        } finally {
            clientSessionEmulator.stopEmulation();
        }

One more advice: take care about threading in SingletonScoped clientSession instance! Wouw, I thought I could do it with less lines 😉 If you like to know more about this approach feel free to contact me.

Answer 1

Your rephrase is indeed considerably simpler 🙂

Your currentUserInfoFactory could make use of RequestContextHolder.getRequestAttributes(). If a session is present and associated with the calling thread, then this will return a non-null object, and you can then safely retrieve the session-scoped bean from the context. If it returns a null, then you should fetch the prototype-scoped bean instead.

It’s not very neat, but it’s simple, and should work.