[jira] Resolved: (JCR-65) ChainedPersistenceManager

["Jukka Zitting (JIRA)" <ji...@apache.org>]

     [ http://issues.apache.org/jira/browse/JCR-65?page=all ]
     
Jukka Zitting resolved JCR-65:
------------------------------

    Resolution: Won't Fix

Resolving this issue as "Won't fix" to clean up the open issues list.

As Edgar already mentioned, there is little support for the idea of adding complexity to the persistence manager layer. I think that we should try to find other solutions to the mentioned needs. Until such a solution is found we can direct people who have needs like this to this issue as an unsupported interim solution.

Please reopen this issue if there is a design change that would favor this kind of an approach.

For reference, see the original discussion thread at:
http://thread.gmane.org/gmane.comp.apache.jackrabbit.devel/911


> ChainedPersistenceManager
> -------------------------
>
>          Key: JCR-65
>          URL: http://issues.apache.org/jira/browse/JCR-65
>      Project: Jackrabbit
>         Type: New Feature
>     Reporter: Edgar Poce
>     Assignee: Jukka Zitting
>     Priority: Minor
>  Attachments: 05-03-15-chained-persistence.zip, uml-class.gif
>
> Overview
> The package contains the classes that provide chaining of Persistence Managers support through an implementation of the chain of responsibility pattern.
> The ChainedPersistenceManager class is the chain's external controller.
> The current implementation uses composition instead of inheritance. The concrete handlers (PersistenceManager) are private members instead of subclasses.
> For reading commands no evaluation is performed, the ChainedPersistenceManager returns the response of the first handler that finds the object.
> For writing commands, the PersistenceManagerHandler class delegates conditionally the persistence calls to the concrete implementation based on a custom evaluation.
> Custom PersistenceManagerEvaluator implementations can be set through configuration.
> Custom listeners can be added to the ChainedPersistenceManager class. It allows to perform custom operations on "after init" and "before close" events. 
> Warning
> This package should be used only in a couple of cases and none of them is the best practice.
>     * Sharing jcr data with others systems through a custom PersistenceManager
>     * Integrating a legacy system
> Reliability, integrity and performance of the PersistenceManager are *crucial* to the overall stability & performance of the repository. if e.g. the data that a PersistenceManager is based upon is allowed to change through external means the integrity of the repository would be at risk (think of referential integrity/ node references e.g.).

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