Struts2 and multiple active wizards / workflows

I'm currently working on a Struts2 application that integrates a wizard / workflow in order to produce the desired results. To make it more clear, there is a business object that is changed on three different pages (mostly with AJAX calls). At the moment I'm using a ModelDriven action (that's extended by all the actions working with the same business object) coupled with the Scope interceptor. While this works okay if the user is handling data for only one business object at a time, if the user opens the wizard for different objects in multiple tabs (and we all do this when we want to finish things faster) everything will get messy, mostly due to the fact that I have only one business object stored in the session.

I have read a few articles about using a Conversation Scope Interceptor (main article) and about using the Scope plug-in (here). However, both approaches seem to have problems:

• the Conversation Scope Interceptor doesn't auto-expire the conversations, nor does it integrate properly with Struts2;
• the Scope plug-in lacks proper documentation and the last build was made in 2007 (and actually includes some of the ideas written by Mark Menard when he defines his Conversation Scope Interceptor, though it doesn't开发者_开发问答 use the same code).

Spring's WebFlow plug-in seems a bit too complex to be used at the moment. I'm currently looking for something that can be implemented in a few hours time, though I don't mind if you can suggest something that works as needed, even if it requires more time than I'd currently want to spend on this now.

So, seasoned Struts2 developers, what do you suggest? How should I implement this?

Okay this isn't a fully baked idea. But seeing as no else has provided anything, here is what I would start with.

1) See if you can move the whole flow into a single page. I'm a big believer in the less pages is better approach. It doesn't reduce complexity for the application at all, but the user generally finds the interface a lot more intuitive. One of the easiest ways to go about this is by using the json plugin and a lot of ajax calls to your json services.

2) If you must transition between pages (or simply think it is too much client side work to implement #1) then I'd look to the s:token tag. The very first page to kick off a flow will use this tag, which will create a unique value each invocation. You will store a map in your session of model objects. An action will need to be provided with a model by looking it up from the session.

There are a couple challenges with #2. One how do you keep the session from getting too many domain objects? a) Well it might not matter, if the session is set to say six hours you can be rather sure that over night they will get cleared up. b) provided a self management interface which can get/set/list objects in the session. It might be what you thought of at first but it would let a worker do a certain amount and then stop and work on another. If the unit of work has some meaningful name (an invoice number or whatever) it could be quite useful.

A little more sophistication would be to move the model objects out of the session and into the service layer. At which point when inserted you would set an insertion time. You would probably need a manager to hold each type of model object and each manager would have a daemon thread that would periodically scan the map of domain objects and clean out expired ones.

You can figure out more complicated system by kicking a flow off with a token and then using another token on each page. "flowId" and "currentPageId" respectively, then you can graph allowable transitions.

Mind you at this point spring web flow is starting to look pretty good.

There is now a conversation plugin for Struts2 that achieves all these goals with very little work required by the developer: http://code.google.com/p/struts2-conversation/

It has: -nested conversations -cleanup of dead conversations -convention over configuration with annotations and naming conventions -inherited conversations -fully integrated with Struts2 -the conversation scope can also be used by Spring IoC container-managed beans

Hope it helps somebody.