log4j.rootLogger 与log4j.rootCategory 有什么区别

下面是在log4j官方的API中写的，足以能解释logger与category的区别。。。

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