Spring webflow 2 concurrency issue

[John Utting]

Hi,

Can someone please explain to me why flowScope.cart is null in the following code in Spring Webflow when 2 threads are hitting the flow at exactly the same time

<var name="handsetModel" class="com.***.***.binding.HandsetModel"/>
<on-start>
	<set name="flowScope.cart" value="externalContext.sessionMap.cart" type="com.***.***.cart.ShoppingCart"/>
</on-start>
<action-state id="decideOnActivityType">
	<evaluate expression="handsetActions.isContractHandset(flowScope.cart)"/>
	<transition on="yes" to="decideOnStartState"/>
	<transition on="no" to="addPaygHandset"/>
</action-state>

here is the isContracthandset method that is called in the 'decideOnActivityType' action state:

public boolean isContractHandset(ShoppingCart cart) {
	if(cart == null){
	    log.info("cart is null");
	}
	log.info("Method call - isContractHandset(): cart "+cart);
	boolean isContractHandset = false;
	if("contractHandset".equals(cart.getActivityTypeString())){
	    isContractHandset = true;
	}
	return isContractHandset;
}

and here is the output from the log:

INFO  Session created ID: 212DFC605416E21C90791898EAD32A1C
INFO  Object added to sssion: Session ID: 212DFC605416E21C90791898EAD32A1C cart com.***.***.cart.ShoppingCart@14c7cd
INFO  Session created ID: 30C4695F2D1737D06B02F5E5B992258E
INFO  Object added to sssion: Session ID: 30C4695F2D1737D06B02F5E5B992258E cart com.***.***.cart.ShoppingCart@497536
INFO  Refreshing org.springframework.web.context.support.GenericWebApplicationContext@b4ac5c: display name [Flow ApplicationContext [contractHandsetSale]]; startup date [Wed Aug 19 09:41:12 GMT 2009]; parent: org.springframework.web.context.support.XmlWebApplicationContext@1bb60ad
INFO  Bean factory for application context [org.springframework.web.context.support.GenericWebApplicationContext@b4ac5c]: org.springframework.beans.factory.support.DefaultListableBeanFactory@70856b
INFO  Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@70856b: defining beans [org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,messageSource]; parent: org.springframework.beans.factory.support.DefaultListableBeanFactory@270fc4
INFO  cart is null
INFO  Method call - isContractHandset(): cart com.***.***.cart.ShoppingCart@14c7cd
INFO  Method call - isContractHandset(): cart null

I have a implemented an HttpSessionAttributeListener so I can confim that there are two shopping carts in separate sessions, but either externalContext.sessionMap.cart is returning null or the value being returned is not being assigned to flowScope.cart. I am usnig webflow 2 spring 2.5.6 and ognl2.6.9. In a single threaded environment i never get any problems.

Thanks John

[Hong Anderson]

Have you proved that the second call use session id 30C4695F2D1737D06B02F5E5B992258E?

[John Utting]

yes i can confirm that once inside the method the method the second call matches has the session id you wouild expect

[Hong Anderson]

I have no idea. You should debug to see why the session is null.

[Trilochan Bharadwaj]

How's the flow being hit? is this JSF External context? can you show snippets of external code hitting web flow?


Trilochan