The retrieval and local caching of the map tiles, as well as the supported viewing options, are all configured in a simple Java properties file. This is the file being handled by this FileHandler.

The contained properties are grouped into general settings, part of which can be manipulated through the GUI, and the setup of map services with their respective local caching strategies.

The properties for general settings all have a "Setting." prefix and these are being used for all setups. Then there is a comma separated list of setup names in the "SetupNames" property of which the "SetupName" property denotes which of them is the active one. The configuration of each setup is then in the properties with a prefix of "Setups.[setupName].".

In each of those property groups for a specific setup, the "Provider" property denotes the service which is being accessed for tile retrieval. The possible provider types are:

The two caching provider types are special, however: they both have a "Provider" sub-property and thus support building provider chains. An example would be a CacheMemory provider which caches tiles in memory that were retrieved from a CacheFile provider that looks up tiles in a local directory first, before ultimately resolving to one of the URL-based providers (GoogleMaps, etc.) to retrieve a missing local tile from the corresponding internet service:

  MapViewerGUI <= CacheMemory <= CacheFile <= GoogleMaps

Another example might be the same caching providers but with an Offline provider at the end of the chain. This could be used to provide access to a local tile repository without any network traffic:

  MapViewerGUI <= CacheMemory <= CacheFile <= Offline

In case there is a "Provider" property without a setup prefix, this will take precedence over the configured setups. It will then behave as if no setup names were configured and thus no further prefix will be used for resolving the provider properties.