[jira] Updated: (SLING-1391) Make JcrModifiablePropertyMap write changes directly

["Justin Edelson (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SLING-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Justin Edelson updated SLING-1391:
----------------------------------

    Fix Version/s:     (was: JCR Resource 2.0.8)

descheduling from current release

> Make JcrModifiablePropertyMap write changes directly
> ----------------------------------------------------
>
>                 Key: SLING-1391
>                 URL: https://issues.apache.org/jira/browse/SLING-1391
>             Project: Sling
>          Issue Type: Improvement
>          Components: JCR
>    Affects Versions: JCR Resource 2.0.6
>            Reporter: Vidar S. Ramdal
>
> As discussed on http://markmail.org/thread/io2dnkykjnayydwz, the current JcrModifiablePropertyMap implementation of the PersistableValueMap interface uses a cached map to store changed values. The cached values are not written to the underlying node until a PVM.save() is called - at which point JMPM calles Node.save() to persist the changes. Thus, reverting changes made in a session is impossible.
> This makes atomic operations such as this difficult to implement:
> try {
>    // Modify a property through PersistableValueMap
>    PersistableValueMap props = resource.adaptTo(PersistableValueMap.class);
>    props.put("prop", value);
>    props.save();
>    // Do some other, unrelated changes
>    Node sibling = resource.adaptTo(Node.class).getParent().addNode("child");
>    sibling.doSomeChange(); // This may throw an exception
>    session.save();
> } catch(Exception e) {
>    session.refresh(false); // Cancel the pending changes of this session
> } 
> Felix suggests (http://markmail.org/message/5fae3cwsshbnemrf):
> * Enable the PersistableValueMap to write through to the JCR
>    transient space on put().
>  * Write-through is configurable on a global level (in the
>    JcrResourceResolver providing the PersistableValueMap
>    instances upon adapt()). By default it is switched off
>    (backwards compatiblity).
>  * Write-through can also be switched on/off on a per-instance
>    level of the PersistableValueMap object (setWriteThrough(boolean))
>  * PersistableValueMap.save() first writes back local changes
>    not already stored using write-through and then calls node.save()
>  * PersistableValueMap.reset() drops local changes not already stored
>    using write-through and then calls node.refresh(false)
>  * When we finally do full CRUD in the ResourceResolver, we should
>    add save/reset methods, which would call Session.save() or
>    refresh(false), resp. For now the Session methods must be called
>    directly.
> This task is about implementing Felix' suggestions.

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