The set of active user conversations are managed by a ConversationService implementation, which this repository delegates to.

This repository is responsible for:

• Beginning a new conversation when a new flow execution is made persistent. Each conversation is assigned a unique conversartion id which forms one part of the flow execution key.
• Associating a flow execution with that conversation by adding a FlowExecutionContinuation to the FlowExecutionContinuationGroup . When a flow execution is placed in this repository a new continuation snapshot is created, assigned an id, and added to the group. Each continuation logically represents a state of the conversation at a point in time that can be restored and continued. These continuations can be restored to support users going back in their browser to continue a conversation from a previous point.
• Ending existing conversations when persistent flow executions end, as part of a repository removal operation.

It is important to note use of this repository allows for duplicate submission in conjunction with browser navigational buttons (such as the back button). Specifically, if you attempt to "go back" and resubmit, the continuation id stored on the page in your browser history will match the continuation id of the FlowExecutionContinuation object and access to the conversation will allowed.

This repository implementation also provides support for conversation invalidation after completion, where once a logical conversation completes (by one of its FlowExecution's reaching an end state), the entire conversation (including all continuations) is invalidated. This prevents the possibility of duplicate submission after completion.

This repository implementation should be considered when you do have to support browser navigational button use, e.g. you cannot lock down the browser and require that all navigational events to be routed explicitly through Spring Web Flow.