26 Oct 2017

Right Way To Declare Java Log

/*
 * which is better?
 * log1 private is better, because so that no other class can hijack your logger
 */
private Logger log1 = LoggerFactory.getLogger(getClass());
public Logger log2 = LoggerFactory.getLogger(getClass());

/*
 * which is better?
 * log4 static is better, because it means we create one Logger per class, not one logger per instance of your class.  
 * Generally, this is what you want - as the loggers tend to vary solely based on class.
 */
private Logger log3 = LoggerFactory.getLogger(getClass());
private static Logger LOG4 = LoggerFactory.getLogger(HowToLog.class); //usually final use uppercase

/*
 * which is better?
 * log6 final make more sense, final means that you're not going to change the value of the logger variable.
 * Which is true, since you almost always throw all log messages (from one class) to the same logger. 
 */
private static Logger LOG5 = LoggerFactory.getLogger(HowToLog.class);
private final static Logger LOG6 = LoggerFactory.getLogger(HowToLog.class);

/*
 * which is better?
 * dependents on how you want your extends class log print:
 * log7 way allows you to use the same logger name (name of the actual class) in all classes 
 * throughout the inheritance hierarchy. So if Bar extends Foo, both will log to Bar logger. Some find it more intuitive.
 *
 * also, want to mentioned is protected not work for the extends class when using the static methods,
 * in that situation, we need to create construct another logger in the child class.
 */
protected final Logger log7 = LoggerFactory.getLogger(getClass());
private static final Logger LOG8 = LoggerFactory.getLogger(HowToLog.class);

/*
 * which is better?
 * I don't know
 * after Java7, we can use 
 * Logger lgr = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());instead of static logger.
 */
private static final Logger LOG9 = LoggerFactory.getLogger(HowToLog.class);
Logger log10 = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

/* you can't really use this.getClass() because this doesn't actually exists (you're running in a static context */
//	private static final Logger logger = LoggerFactory.getLogger(this.getClass().getName());