in spring/src/main/java/org/apache/logging/log4j/boot/spring/Log4jLoggingSystem.java [137:143]
protected void loadConfiguration(final LoggingInitializationContext context, final String location,
final LogFile ignored) {
// log file name is available via ${sys:LOG_FILE} (see log4j2-file.xml default config)
final URI configLocation = NetUtils.toURI(location);
loggerContext = (LoggerContext) LogManager.getContext(
getClassLoader(), false, this, configLocation);
}