How about change `switch ... case` to the Enum methods?
Something like this:
```java
private enum Level {
		FATAL {
			boolean enabled() {
				return LoggingHandler.this.messageLogger.isFatalEnabled();
			}

			void log(Object message) {
				LoggingHandler.this.messageLogger.fatal(message);
			}
		},
.....
protected void handleMessageInternal(Message<?> message) throws Exception {
   if (this.level.enabled()) {
       this.level.log(this.toLogMessage(message));
    }
```