Hi,
If the File or URL is writable, will writing to the location cause issues
for Oak ?
IIRC some Oak DS implementations use a digest of the content to determine
the location in the DS, so changing the content via Oak will change the
location, but changing the content via the File or URL wont. If I didn't
remember correctly, then ignore the concern. Fully supportive of the
approach, as a consumer of Oak. The locations will certainly probably leak
outside the context of an Oak session so the API contract should make it
clear that the code using a direct location needs to behave responsibly.
Best Regards
Ian
On 3 May 2016 at 15:36, Chetan Mehrotra <chetan.mehro...@gmail.com> wrote:
> Hi Team,
>
> For OAK-1963 we need to allow access to actaul Blob location say in form
> File instance or S3 object id etc. This access is need to perform optimized
> IO operation around binary object e.g.
>
> 1. The File object can be used to spool the file content with zero copy
> using NIO by accessing the File Channel directly [1]
>
> 2. Client code can efficiently replicate a binary stored in S3 by having
> direct access to S3 object using copy operation
>
> To allow such access we would need a new API in the form of
> AdaptableBinary.
>
> API
> ===
>
> public interface AdaptableBinary {
>
> /**
> * Adapts the binary to another type like File, URL etc
> *
> * @param <AdapterType> The generic type to which this binary is
> adapted
> * to
> * @param type The Class object of the target type, such as
> * <code>File.class</code>
> * @return The adapter target or <code>null</code> if the binary cannot
> * adapt to the requested type
> */
> <AdapterType> AdapterType adaptTo(Class<AdapterType> type);
> }
>
> Usage
> =====
>
> Binary binProp = node.getProperty("jcr:data").getBinary();
>
> //Check if Binary is of type AdaptableBinary
> if (binProp instanceof AdaptableBinary){
> AdaptableBinary adaptableBinary = (AdaptableBinary) binProp;
>
> //Adapt it to File instance
> File file = adaptableBinary.adaptTo(File.class);
> }
>
>
>
> The Binary instance returned by Oak
> i.e. org.apache.jackrabbit.oak.plugins.value.BinaryImpl would then
> implement this interface and calling code can then check the type and cast
> it and then adapt it
>
> Key Points
> ========
>
> 1. Depending on backing BlobStore the binary can be adapted to various
> types. For FileDataStore it can be adapted to File. For S3DataStore it can
> either be adapted to URL or some S3DataStore specific type.
>
> 2. Security - Thomas suggested that for better security the ability to
> adapt should be restricted based on session permissions. So if the user has
> required permission then only adaptation would work otherwise null would be
> returned.
>
> 3. Adaptation proposal is based on Sling Adaptable [2]
>
> 4. This API is for now exposed only at JCR level. Not sure should we do it
> at Oak level as Blob instance are currently not bound to any session. So
> proposal is to place this in 'org.apache.jackrabbit.oak.api' package
>
> Kindly provide your feedback! Also any suggestion/guidance around how the
> access control be implemented
>
> Chetan Mehrotra
> [1] http://www.ibm.com/developerworks/library/j-zerocopy/
> [2]
>
> https://sling.apache.org/apidocs/sling5/org/apache/sling/api/adapter/Adaptable.html
>
