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https://issues.apache.org/jira/browse/LANG-482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12675777#action_12675777
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Rob Walker commented on LANG-482:
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Thanks - I'll need to take a look at these. The changes are working nicely to 
great benefit in our usage with a Felix based App here, but clearly they trip 
out some of the standard tests.
 - Rob

> Enhance StrSubstitutor to support nested ${var-${subvr}} expansion
> ------------------------------------------------------------------
>
>                 Key: LANG-482
>                 URL: https://issues.apache.org/jira/browse/LANG-482
>             Project: Commons Lang
>          Issue Type: Improvement
>            Reporter: Rob Walker
>            Priority: Minor
>         Attachments: StrSubstitutor.java.nested.patch
>
>
> t would be really handy of StrSubstitutor could support nested variable 
> interpolation:
> org.osgi.framework.system.packages=org.osgi.framework; version=1.4.0, \
> org.osgi.service.packageadmin; version=1.2.0, \
> org.osgi.service.startlevel; version=1.1.0, \
> org.osgi.service.url; version=1.0.0, \
> org.osgi.util.tracker; version=1.3.3 \
> ${jre-${java.specification.version}}
> The process being to expand innermost variable references first and work 
> outwards - this allows for very advance config, such as the above, which can 
> dynamically detect the Java version and expand a JRE version specific 
> property into the property being defined.
> Looking at the implementation, it seems it might be a fairly straightforward 
> enhancement to:
> private int substitute(StrBuilder buf, int offset, int length, List 
> priorVariables)
> The code already has the cyclic map in place.
> I already have code that achieves this within Apache Felix, so I will see if 
> I can retro-fit a similar model to the above and if so submit a patch. 

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