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https://issues.apache.org/jira/browse/JCR-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13651138#comment-13651138
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Alexander Klimetschek commented on JCR-3534:
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The main point is actually that the signature MUST be created inside the
repository implementation, I can't see how client code would have access to the
data store secret which is required to create the signature.
This leads to changing JackrabbitValue#getContentIdentity(): I did not find a
use of getContentIdentity() in our proprietary code; jackrabbit itself only
provides it, but there is no utility etc. making use of it. I wonder what you
could actually do with it so far other than checking for equality to a content
id fetched from somewhere else? But if the hmac signature is expected to change
every time, this would break the api contract afaics, which clearly states "If
two values have the same identifier, the content of the value is guaranteed to
be the same". This forces to add a new API that gives this signed message, no
way around that afaics.
That would be my proposal:
- BinaryReferenceMessage just a data object holding a "token/message" string
(passed via constructor and read via getter)
- other Binary methods empty/no-op
- message format creation including signature done inside new API (e.g.
JackrabbitValue#getSecureContentIdentity())
- message format parsing and signature validation all happening inside
createValue(Binary) when it sees a BinaryReferenceMessage
> 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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