Hello Diego,

The special syntax originates from Bash, at least that's where I saw it fist.

http://www.faqs.org/docs/abs/HTML/parameter-substitution.html
http://tldp.org/LDP/abs/html/refcards.html#AEN20779
http://www.purinchu.net/wp/2005/06/11/advanced-parameter-substitution-with-bash/

Thus, "${varnname:-word}" means, if varname exists and isn't null, return its 
value, otherwise return 'word'.

If my memory serves me correctly, the special substitution syntax is needed 
because, we would like to have the name of the parameter to vary with the 
circumstances. More precisely, while most database drivers take expect the name 
of the "url" parameter to be "url", some database drivers expect that the value 
be passed using a different variable name.

Does this help?

Diego Louzán wrote:
> In chapter4 of the documentation the following example is shown:
> 
> <dataSource class="${dataSourceClass}">
>      <!-- Joran cannot substitute variables
>           that are not attribute values. Therefore, we cannot
>           declare the next parameter like the others.
>      -->
>      <param name="${url-key:-url}" value="${url_value}"/>
>      <serverName>${serverName}</serverName>
>      <databaseName>${databaseName}</databaseName>
> </dataSource>
> 
> I can't figure out that special syntax for Joran in "${url-key:-url}", 
> can anybody explain it to me? Why is it needed in that example?
> 
> Regards.
> Diego.
-- 
--
Ceki Gülcü
QOS.ch is looking to hire talented developers located in Switzerland.
If interested, please contact c e k i AT q o s . c h
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