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From "Michiel Kalkman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CONFIGURATION-215) Using relative URLs
Date Fri, 16 Jun 2006 11:08:30 GMT
    [ http://issues.apache.org/jira/browse/CONFIGURATION-215?page=comments#action_12416477
] 

Michiel Kalkman commented on CONFIGURATION-215:
-----------------------------------------------

Knowing in which location a certain configuration item was specificied, would help in implementing
a getURL() method on the configuration interface. Maybe it would also be useful for debugging
purposes, e.g. when a configuration item is specified in multiple locations, it could be used
to determine which one was chosen.

I think it's important to keep the configuration files as simple and intuitive as possible
in order to make usage and specification of configurations as easy. In particular, you don't
want a programmer to know how the configuration is structured; except for the location of
the root configuration, and the names / types of the configuration items, he should know nothing
more.

So, option 1 is still my favorite solution. Maybe that for some options this can not be implemented
(JNDI comes to mind - but I never used that in combination with commons configuration).

> Using relative URLs
> -------------------
>
>          Key: CONFIGURATION-215
>          URL: http://issues.apache.org/jira/browse/CONFIGURATION-215
>      Project: Commons Configuration
>         Type: Improvement

>     Reporter: Michiel Kalkman
>     Priority: Minor

>
> It would be useful to be able to specify URLs in configuration item values that are relative
to the configuration.
> A sample. I have the following files.
> A/config.xml   which refers to    
> B/specificConfigForB.xml   which refers to
> B/somefile
> Now specifying the location of somefile in specificConfigForB.xml should be possible
using a relative URL, such that it is possible to retrieve the absolute URL of somefile through:
> a) the absolute URL of A/config.xml (e.g.: file:/c:/A/config.xml or http://A/config.xml)
> b) the relative URL of somefile specified in B/specificConfigForB.xml (like <somefile>somefile</somefile>)
> (1) One solution is to make it possible to find the location of the configuration file
that specifies the relative URL. Or more general, commons config should know where a given
configuration item is stored.
> In this case it might be an idea to implement a getURL() on the Configuration interface
which uses:
> 1. the absolute URL of the composite configuration file, (A/config.xml)
> 2. the relative URL to the specfying configuration file, (B/specificConfigForB.xml)
> 3. the relative URL specified (in B/specificConfigForB.xml)
> (2) Another solution is to specify a special meta variable (like ${url}) that can be
used to specify the location of the specifying configuration file wrt the composite configuration
file. E.g. <somefile>${url}/somefile</somefile> would result in ../B/somefile.
> (3) Another solution would be to specify a special attribute to indicate that the value
specified is an URL. Like <somefile type="URL">somefile</somefile>.
> The advantage of solution (1) is that no extra semantics are introduced to the configuration
files. Furthermore, it might possibly be useful in debugging situations. The advantages of
solution (2) is that in this manner other meta variables might be introduced. The disadvantage
of solution (3) is that this one cannot be applied to property files.
> See also http://mail-archives.apache.org/mod_mbox/jakarta-commons-user/200606.mbox/%3c448AE9A8.2030003@oliver-heger.de%3e

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