[LANG-482] Enhance StrSubstitutor to support nested ${var-${subvr}} expansion

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0
• Component/s: lang.text.*
• Assignee: Unassigned
• Reporter: Rob Walker
• Created: 06/Feb/09 13:25
• Updated: 02/May/13 02:29
• Resolved: 08/Oct/10 19:24

Description

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.

Issue Links

• is depended upon by: CONFIGURATION-363 Consider enhancing to allow nested variable interpolation