Log4j Concepts

Internal

• log4j

Logger

Logger is a subclass of Category and extends it. Category has been deprecated.

Category

This class has been deprecated and replaced with the Logger subclass.

*

Logger is a subclass of Category, i.e. it extends * Category. In other words, a logger is a category. Thus, * all operations that can be performed on a category can be * performed on a logger. Internally, whenever log4j is asked to * produce a Category object, it will instead produce a Logger * object. Log4j 1.2 will never produce Category objects but * only Logger instances. In order to preserve backward * compatibility, methods that previously accepted category objects * still continue to accept category objects. * *

For example, the following are all legal and will work as * expected. *

       // Deprecated form:
       Category cat = Category.getInstance("foo.bar")
   
       // Preferred form for retrieving loggers:
       Logger logger = Logger.getLogger("foo.bar")
   

*

The first form is deprecated and should be avoided. * *

There is absolutely no need for new client code to use or * refer to the Category class. Whenever possible, * please avoid referring to it or using it. * *

See the <a href="../../../../manual.html">short manual</a> for an * introduction on this class. *

* See the document entitled <a href="http://www.qos.ch/logging/preparingFor13.html">preparing * for log4j 1.3</a> for a more detailed discussion. *