On Mon, Jun 22, 2020 at 10:52 AM Андрей Троицкий
<[email protected]> wrote:
>
> Hi everybody,
> I have a question regarding the functionality of Jackrabbit WebDAV server.
>
> We have run a standard server and uploaded some files in it. When we upload a
> new file with the same name we need to check if the file on the server is up
> to date and shouldn't be replaced. The initial idea was to use ETags but we
> found it's weak and is not suitable for the application. So now the idea is
> to check the checksum (hash) of the incoming and existing files. As files can
> be pretty big and downloading everytime can be a time-consuming operation,
> it's better to have an option to easily obtain checksum for already uploaded
> files.
>
> So my question: are there any options to get a checksum for files uploaded to
> the server? Maybe there are some other options or features that will help in
> such file handling?
I don't think there's a built-in feature to retrieve the hash of the
file content in WebDAV or Jackrabbit WebDAV.
If it is feasible to use JCR API and add a custom code (e.g, servlet)
in addition to the default JR WebDAV servlet for example, then the
following info might be helpful:
- JR WebDAV is just a WebDAV binding for JCR, and Jackrabbit JCR uses
DataStore to save binary (file) content which exceeds the threshold
size setting. [1]
- And DataStores calculates and uses hash values for each binary data
item. The identifier, the hash value, can be retrieved using
Jackrabbit API. [2] For example,
import org.apache.jackrabbit.api.JackrabbitValue;
//...
String binaryId = ((JackrabbitValue)
node.getProperty("jcr:data").getValue()).getContentIdentity();
So, it is technically possible to let a custom code read and respond
with the hash value on existing file item's binary data even though it
will require time/effort looking into the JCR node structure/API in
detail.
Regards,
Woonsan
[1] http://jackrabbit.apache.org/archive/wiki/JCR/DataStore_115513387.html
[2]
http://jackrabbit.apache.org/archive/wiki/JCR/DataStore_115513387.html#DataStore-RetrievetheIdentifier
>
> Thanks in advance for your reply!
> Regards
> Andrey
