Include defaults in interpolation

[ronaldvanrij]

We've had some situations in which we needed to specify defaults and be included in variable interpolation. For example a default could be a parametrized path to certain resources, while the loaded properties file would simply contain the referenced variables, i.e.:

default as hashmap:
[base_path: "/${application}/${environment}/${version}"]

loaded properties file

application=My Application
environment=DEV
version=1.0.0

Current workaround would be to serialize this hashmap into a string and provide this to the readProperties method, but this seems the be a convoluted approach. This tweaks allows you to use the defaults parameter and have those defaults be included into the string interpolation.

[rudolfwalter]

@rsandell This would be very useful for us as well, could you take a look at this? :)