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https://issues.apache.org/jira/browse/HDFS-6464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14013705#comment-14013705
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Yi Liu commented on HDFS-6464:
------------------------------

Discussed with Uma about xattr.names parameter format:

*xattr.names=name1,name2,name3...*
Each name<1-n> is an xattr name, we are intended to use comma as delimiter. 
Because xattr name can be any string prefixed with 
(user\\.|trusted\\.|system\\.|security\\.), it may contain comma, we need to do 
some form of encoding for each xattr name.
To be convenient for user input, we choose URL encoding. If user knows the 
xattr name only contains [A-Za-z0-9._-], then he doesn't need to do URL 
encoding, because encoding result is the same.
For example, if the xattrs are user.a1, user.a2, user.a3, the parameter is 
{{xattr.names=user.a1,user.a2,user.a3}}

We need to document this and give an example.

> Add xattr.names parameter for WebHDFS getXAttrs.
> ------------------------------------------------
>
>                 Key: HDFS-6464
>                 URL: https://issues.apache.org/jira/browse/HDFS-6464
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: webhdfs
>    Affects Versions: 3.0.0
>            Reporter: Yi Liu
>            Assignee: Yi Liu
>             Fix For: 3.0.0
>
>
> For WebHDFS getXAttrs through names, right now the entire list is passed to 
> the client side and then filtered, which is not the best choice since it's 
> inefficient and precludes us from doing server-side smarts on par with the 
> Java APIs. 
> Furthermore, if some xattrs doesn't exist, server side should return error.



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