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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Commented] (OAK-144) Implement observation
Date Thu, 21 Jun 2012 16:21:43 GMT

    [ https://issues.apache.org/jira/browse/OAK-144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13398525#comment-13398525

Michael Dürig commented on OAK-144:

At revision 1352593 I committed another draft implementation for observation which covers
some middle ground of what we [discussed | http://markmail.org/message/osxupy3twc3pyild] on

* No queueing of events to be delivered
* Pull events from oak-core and calculate them on the fly
* No background thread in oak-core

In oak-core the implementation hooks into refresh and remembers a limit (revision) up to which
events should be generated. No additional state is kept for observation in oak-core. Clients
of oak-core use an instance of {{ChangeExtractor}} which can be obtained from {{Root}} and
which allows to extract changes by passing a {{NodeStateDiff}} instance to its 
{{getChanges}} method. Each call to {{getChanges}} carries on where the previous call has

In oak-jcr each observation listener is associated with a {{ChangeExtractor}} and a timer
on a background thread is used to call the {{getChanges}} methods regularly. This is the place
where JCR events should be created, filtered and sent to the {{EventListener}}. This is currently
work in progress and not yet implemented. 
> Implement observation
> ---------------------
>                 Key: OAK-144
>                 URL: https://issues.apache.org/jira/browse/OAK-144
>             Project: Jackrabbit Oak
>          Issue Type: Task
>          Components: core, jcr
>            Reporter: Michael Dürig
>            Assignee: Michael Dürig

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