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From "Felix Meschberger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-2640) Internal repository context
Date Thu, 27 May 2010 13:34:29 GMT

    [ https://issues.apache.org/jira/browse/JCR-2640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12872216#action_12872216
] 

Felix Meschberger commented on JCR-2640:
----------------------------------------

> The point is to avoid public getters of internal components in RepositoryImpl. 

I think this is not enough of an argument.

If we go modularized and we have properly exported API and poperly shielded implementation
classes (as is possible e.g. with OSGi Export-Package specs) we don't have to worry about
public methods of implementation classes which are used by the public by means of API.

The only way for the user to access such publich methods is by using Reflection... But by
using Reflection you can do anything you want, and non-public methods are not protected from
being used at all.

Thus I agree with Tobias, that defining an interface is sufficient.

I also agree with Thomas, that trying to prevent publich methods to help modularize stuff
is completely wrong and makes things way too complex and in the end probably prevents proper
modularization.

> Increased modularity comes with increased complexity. Unneeded complexity will make our
lives harder, not
> easier. I'm afraid we bloat the code unnecessarily.

To a certain extent yes. But modularization is about separation of concerns, is about hiding
implementation from the users. If we don't go that route, we can just as well keep the *Impl
casts ;-)

> Internal repository context
> ---------------------------
>
>                 Key: JCR-2640
>                 URL: https://issues.apache.org/jira/browse/JCR-2640
>             Project: Jackrabbit Content Repository
>          Issue Type: Improvement
>          Components: jackrabbit-core
>            Reporter: Jukka Zitting
>            Assignee: Jukka Zitting
>         Attachments: repository-context-v1.patch, repository-context.png
>
>
> As discussed in JCR-890, the current approach of using protected or package-private getters
on key classes like RepositoryImpl to access other internal components and resources is a
bit troublesome. The attached patch (repository-context-v1.patch) introduces a RepositoryContext
object that can be used to get rid of such getters. This first version replaces the getNamespaceRegistry(),
getNodeTypeRegistry(), getVersionManager() and getRootNodeId() methods from RepositoryImpl.
> The idea behind this component context idea is to separate the JCR API implementation
classes from the task of keeping track of the internal implementation components. This way
none of the instances returned by JCR API methods would have methods through which Jackrabbit
internals can be directly accessed. See the attached UML diagram for how this layered access
would work.
> Assuming people think this is a good idea, I'd like to extend this mechanism to cover
also the rest of the internal Repository components like the data store and the security managers,
etc. I'm also thinking about using a similar context objects for tracking internal components
associated with workspaces (WorkspaceInfo, SharedItemStateManager, etc.) and sessions (LocalItemStateManager,
etc.).
> PS. Yes, we'd get much of the same functionality (and more) from OSGi or an IoC container.
For now I'm hoping to keep things simple without extra external dependencies.

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