log4j.rootLogger 與log4j.rootCategory 有什麼區別

下面是在log4j官方的API中寫的，足以能解釋logger與category的區別。。。

public class Category

extends java.lang.Object

implements AppenderAttachable

This class has been deprecated and
replaced by the Logger subclass. It
will be kept around to preserve backward compatibility until mid
2003.

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 short manual for an
introduction on this class.

See the document entitled preparing
for log4j 1.3 for a more detailed discussion.

Author:

Ceki Gülcü, Anders Kristensen