in log4j-api-to-jul/src/main/java/org/apache/logging/log4j/tojul/JULLoggerContext.java [51:61]
public ExtendedLogger getLogger(final String name, final MessageFactory messageFactory) {
final MessageFactory effectiveMessageFactory =
messageFactory != null ? messageFactory : DEFAULT_MESSAGE_FACTORY;
final ExtendedLogger oldLogger = loggerRegistry.getLogger(name, effectiveMessageFactory);
if (oldLogger != null) {
return oldLogger;
}
final ExtendedLogger newLogger = createLogger(name, effectiveMessageFactory);
loggerRegistry.putIfAbsent(name, effectiveMessageFactory, newLogger);
return loggerRegistry.getLogger(name, effectiveMessageFactory);
}