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https://issues.apache.org/struts/browse/WW-1514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_42511
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Tom Schneider commented on WW-1514:
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I already started a googlecode project for this:
http://code.google.com/p/struts2scopeplugin/ Instead of implementing Mark's
code directly, I've added Seam's Begin and End annotations so the conversation
demarcation can be added. I also want to look into whether we can do the
'autoflash' stuff that Seam does, so conversation scoped parameters can survive
a redirect. I also plan on beefing up the documentation. I think I would
prefer to work on my changes in the googlecode project, then if it gets to a
point where we like it, we can move it back at that point. (At that point it
should be ready as a normal plugin) I really want to follow Seam as much as
possible--and then the web beans spec once it's available.
> Conversation Scope
> ------------------
>
> Key: WW-1514
> URL: https://issues.apache.org/struts/browse/WW-1514
> Project: Struts 2
> Issue Type: New Feature
> Components: Core Interceptors
> Reporter: Mark Menard
> Priority: Minor
> Fix For: 2.1.1
>
> Attachments: ConversationModelDriven.java,
> ConversationModelInterceptor.java, ConversationScopeAware.java,
> ConversationScopeInterceptor.java
>
>
> Problem: A user may need to, or be able to use, multiple tabs on the same
> work flow process, using different data, that would usually be stored in the
> user's session. The problem is if you use the Session scope you can only have
> one version of the users data in memory. This can result in a "crossing of
> the streams" between their two (or more) independent work flows. Ad-hoc
> solutions on a per action basis could be implemented, but this is awkward at
> best.
> Example: User opens two processes of the same type, using the same action(s),
> in separate tabs in their browser, working on independent data sets. Each
> data model must be stored separately in their session.
> Solution: Implement a "Conversation Scope" using an Interceptor and a marker
> interface for Actions to implement that will transparently manage multiple
> independent conversations of the same type on independent data sets.
> ConversationScopeInterceptor: This interceptor does the hard lifting. It
> maintains a conversationMap in each users session that allows for the storage
> of multiple converstaionModels. The conversationModels are keyed using an
> incrementing int, and the current time in milliseconds when the conversation
> began. The incrementing of the conversation counter is synchronized.
> Additionally the interceptor pushes the conversationModel onto the ValueStack
> much the same way as ModelDriven pushes the model onto the ValueStack.
> ConversationScopeAware: This is a marker interface for Actions to implement.
> It includes methods to set/get the conersationId, set/get/prepare the
> conversationModel. prepareConversationModel() is called at the start of a
> conversation and allows the action to prepare the data model the user will be
> working with over the conversation.
> Motivation: The major motivation for this was work that we did in Struts 1 to
> work around the pervasive use of session forms. We realized that users could
> cross the streams with multiple forms in memory. To work around this we
> created a deep Action hierarchy that handled swapping the "conversation" data
> into and out of a Map backed form. Although Struts 2 does not suffer from the
> same pervasive need to use session forms there are times when a conversation
> is needed and with modern browsers and the wide usage of tabs, it is just a
> matter of time before a user opens two tabs on the same type of conversation.
> View requirements: In order to track the conversation the HTML form must
> contain:
> <input type="hidden" name="S2_CONVERSATION_ID" value="<the_current
> conversation_id">
> The current conversation id is available as a property of any Action that
> implements ConversationScopeAware and can be included with the following:
> <s:hidden name="S2_CONVERSATION_ID" value="%{conversationId}" />
> Possible Improvements: Slip stream this right into ModelAware, and just use
> getModel() from the ModelAware interface and supplement it with set and
> prepare methods. I didn't want to do that initially because I'm not sure it
> would be appropriate, nor do I like non-explicit things. It would make moving
> a model aware action to a conversation model scope easier, but using
> coversationModel just means changing getModel() to getConversationModel() in
> your action.
> Additionally this could be improved by setting the conversatonId onto the
> ValueStack, and retrieving it off the stack in the view. This would allow for
> the removal of the get/setConversationId() from the ConversationScopeAware
> interface. I just couldn't figure out how to do that.
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