Just wanted to point out a Java library which is actually reasonably well known anyway - TypeSafe’s config library.
This provides an API for loading configuration data from external files. Among other things, it allows properties files to:
- include references to variables (whose values can be defined as sysvars, in code, or in the config files)
- include the contents of other files
- define times with syntax such as “10 seconds” and memory-sizes such as “512k”
More interestingly it supports a superset of JSON called HOCON which allows comments, and which removes the verbosity and unforgiving punctuation requirements of JSON while retaining its powerful nested structure.