Lookup order:
TODO rethink whole default PropertySources and ordering:
TODO introduce default values or constants for ordinals
System properties (ordinal 400)
Environment properties (ordinal 300)
JNDI values (ordinal 200)
Properties file values (/META-INF/applicationConfiguration.properties) (ordinal 100)
Important Hints for custom implementations:
If a custom implementation should be invoked
before the default implementations, use a value > 400
If a custom implementation should be invoked
after the default implementations, use a value < 100
Reordering of the default order of the config-sources:
Example: If the properties file/s should be used
before the other implementations,
you have to configure an ordinal > 400.