public static ApplicationConfiguration readConfiguration(final String... resources) {
if (resources == null) return new ApplicationConfiguration(ImmutableMap.of());
final HashMap<String, String> result = new HashMap<>();
for (String resource : resources) {
if (StringTools.isNullOrEmpty(resource)) continue;
// Read anything from an external config file or resource
if (FileTools.fileExistsAndCanRead(resource)) {
mergeConfigMaps(readConfigFileLines(resource), result);
} else {
mergeConfigMaps(ResourceTools.readResourceTextFileAsMap(resource), result);
}
}
// Check for system properties/envs for overrides
// for the known configuration options and apply them
// as overrides
final Map<String, String> environmentMatches =
MapTools.intersectKeysCaseInsensitive(result, System.getenv());
for (Map.Entry<String, String> matchEntry : environmentMatches.entrySet()) {
final String envOverride = System.getenv().get(matchEntry.getValue());
if (!StringTools.isNullOrEmpty(envOverride)) {
result.put(matchEntry.getKey(), envOverride);
}
}
// Ultimately - command-line properties override everything
final Map<String, Object> propertiesMatches =
MapTools.intersectKeys(
result,
System.getProperties(),
String::toLowerCase,
key -> {
if (key instanceof String) {
return ((String) key).toLowerCase();
} else {
// Do not support non-string matching
return UUID.randomUUID().toString();
}
});
for (Map.Entry<String, Object> matchEntry : propertiesMatches.entrySet()) {
final Object propertiesOverride = System.getProperties().get(matchEntry.getValue());
if (propertiesOverride instanceof String
&& !StringTools.isNullOrEmpty((String) propertiesOverride)) {
result.put(matchEntry.getKey(), (String) propertiesOverride);
}
}
return new ApplicationConfiguration(ImmutableMap.copyOf(result));
}