Java Doc for Log.java in  » Ajax » zk » org » zkoss » util » logging » Java Source Code / Java DocumentationJava Source Code and Java Documentation

private static final Log log = Log.lookup(MyClass.class);
...
if (log.debugable()) log.debug("the information to log:"+some);

Log is designed to minimize the memory usage by avoiding unnecessary allocation of java.util.logging.Logger. In additions, it is possible to use different logger, e.g., log4j, without affecting the client codes.

Since this object is very light-weight, it is OK to have the following statement without using it.
private static final Log log = Log.lookup(MyClass.class);

To log error or warning, simple use the error and warning method.

To log info, depending on the complexity you might want to test infoable first.

log.info("a simple info");
 if (log.infoable())
 log.info(a + complex + string + operation);

To log debug information, we usually also test with D.

log.debug("a simple info");
 if (D.ON && log.debugable())
 log.debug(a + complex + string + operation);

There is a special level called FINER whose priority is lower than DEBUG. It is generally used to log massive debug message under certain situation. In other words, it is suggested to use the debug methods to log messages as follows:

if (log.finerable()) {
 ... do massive testing and/or printing (use finer)
 }

Since debug messages are rarely disabled, there is no method like infoable or debuggable.

Since error messages hardly happens and are rarely disabled, there is no method like infoable or debuggable.

Since info messages are rarely disabled, there is no method like infoable or debuggable.

On the other hand, if the loggers don't support hierarchy, all Log instances are actually mapped to the same Logger called "org.zkoss". The performance is better in this mode.

Default: false.

Note: Once LogService is initialized, Log.setHierarchy is called automatically to turn on the hierarchy support.

All log methods eventaully invokes this method to log messages.
Parameters:
  t - the throwable object; null to ignore

Since warning messages are rarely disabled, there is no method like infoable or debuggable.