Re: [orion-dev] One more question about Server API / File API

[Maciej contractor Bendkowski <maciej.bendkowski@xxxxxxxxxx>]

Hi Vitaly,

The ETag is basically meant to be used
in HTTP cache, so it's quite natural why it's used in HTTP headers along
with the location.
In order to better understand why the
Location and ETag headers are duplicated in the JSON response, please consider
the following scenario.

You are implementing a custom file system
plugin for Orion, e. g. google drive. If you take a look at the File API,
you'll see why the Location property
is crucial there. You could use it for
whatever reason to access the whole file system and perform some operations.
Not only on the file which is actually 
created, updated or whatever. A more
intuitive example is a file system where there's actually no update operation,
but only create. How to implement
an update operation over such a file
system? You could manually check the file versions, and if it's new, delete
the old version using it's location property and save the
new one. 

Why duplicate the ETag? Again, imagine
a file system where all operations take a lot of time to finish. Why not
implement your own cache?
In order to accomplish that without
the ETag you'd probably create your own md5 sum or whatever and manually
check the versions.
That could be done, but it's error prone
and actually slow. So, in this situation the ETag is quite usefull.

I hope that answers your question.

Best regards,
Maciej Bendkowski



From:      
 "Kozyura, Vitaly"
<v.kozyura@xxxxxxx>
To:      
 "orion-dev@xxxxxxxxxxx"
<orion-dev@xxxxxxxxxxx>, 
Date:      
 2013-08-08 11:33
Subject:    
   [orion-dev]
One more question about Server API / File API
Sent by:    
   orion-dev-bounces@xxxxxxxxxxx

---

Hi all,
 
I have one more question about Orion File
API.
Below is the example response from the
wiki page  (http://wiki.eclipse.org/Orion/Server_API/File_API#Copying_a_file_or_directory).
 
Example Response 
HTTP/1.1 201 Created
Location: http://example.com/file/MyProj/destination.txt
ETag: "35fd43td3"
Content-Type: application/json
 
{
"Name" : "destination.txt",
"Location" : "http://example.com/file/MyProj/destination.txt",
"ETag" : "35fd43td3",
"LocalTimeStamp" : "01234345009837",
"Directory" : "true"
"Attributes" : {
"ReadOnly" : "false",
"Executable" : "true"
}
}
 
The ETag and the Location are duplicated
in the header and in the body.
Is there some reason behind ?
 
 
Thanks in advance,
Vitaly
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