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https://issues.apache.org/jira/browse/JCR-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13650878#comment-13650878
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Alexander Klimetschek commented on JCR-3534:
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Looks good. But some more comments ;-)
Since the BinaryReferenceMessage is API, I would keep it as minimal as possible:
- Any key generation should come from the repository itself. Currently it's
mixed - generating is done by the client (needs to know the right format) and
later reading & validating is done by the repository in createValue(). It
should all be done by the repository, the client code should not have to know
the format of the signature. I was thinking that we change the
JackrabbitValue#getContentIdentity() [0] to return the final secure/signed
token format. Should be possible to detect old and new IDs IMHO. This requires
that other code (where?) that uses the content identity can work with the new
format as well.
- BinaryReferenceMessage should go into jackrabbit-api instead of
jackrabbit-jcr-commons since it's a specific Jackrabbit API and jcr-commons is
more about utilities around both JCR API users and JCR implementors, which
makes it hard to find actual jackrabbit specific features
- BinaryReferenceMessage also implements getStream(), read() and getSize() by
providing the message token - IMHO that is misleading if it is used as special
interface only. These should probably return null. The repository itself would
never return such a Binary itself.
[0]
http://jackrabbit.apache.org/api/2.4/org/apache/jackrabbit/api/JackrabbitValue.html#getContentIdentity()
> Efficient copying of binaries across repositories with the same data store
> --------------------------------------------------------------------------
>
> Key: JCR-3534
> URL: https://issues.apache.org/jira/browse/JCR-3534
> Project: Jackrabbit Content Repository
> Issue Type: New Feature
> Components: jackrabbit-api, jackrabbit-core
> Affects Versions: 2.6
> Reporter: Felix Meschberger
> Assignee: Tommaso Teofili
> Attachments: JCR-3534.2.patch, JCR-3534.3.patch, JCR-3534.patch,
> JCR-3534.patch
>
>
> we have a couple of use cases, where we would like to leverage the global
> data store to prevent sending around and copying around large binary data
> unnecessarily: We have two separate Jackrabbit instances configured to use
> the same DataStore (for the sake of this discussion assume we have the
> problems of concurrent access and garbage collection under control). When
> sending content from one instance to the other instance we don't want to send
> potentially large binary data (e.g. video files) if not needed.
> The idea is for the sender to just send the content identity from
> JackrabbitValue.getContentIdentity(). The receiver would then check whether
> the such content already exists and would reuse if so:
> String ci = contentIdentity_from_sender;
> try {
> Value v = session.getValueByContentIdentity(ci);
> Property p = targetNode.setProperty(propName, v);
> } catch (ItemNotFoundException ie) {
> // unknown or invalid content Identity
> } catch (RepositoryException re) {
> // some other exception
> }
> Thus the proposed JackrabbitSession.getValueByContentIdentity(String) method
> would allow for round tripping the JackrabbitValue.getContentIdentity()
> preventing superfluous binary data copying and moving.
> See also the dev@ thread
> http://jackrabbit.markmail.org/thread/gedk5jsrp6offkhi
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