Editing Log4j

=Concepts=
Log4j has teh following fundamental objects: 
* logger
* categories, 
* [[#Priority|priorities (levels)]], 
* appenders and 
* layouts. 

==Logger/Category==
Loggers are named entities and sub classes of category. Logger names are case-sensitive and they follow the hierarchical naming rule. A logger is said to be an ancestor of another logger if its name followed by a dot is a prefix of the descendant logger name. Eine Referenz auf die Instanz des Root-Loggers kann mit der statischen Funktion 
 Logger.getLooger("<NAME>");
geholt werden.

The '''root logger''' resides at the top of the logger hierarchy. It is exceptional in two ways:
#it always exists,
#it cannot be retrieved by name, but by Logger.getRootLogger().

==Priority==
Loggers may be assigned levels. The set of possible levels, that is:
* TRACE
* DEBUG
* INFO
* WARN
* ERROR
* FATAL
Priority objects have both a string name and an integer value. The name is simply a mnemonic label for the priority. The integer value defines a relative order amongst priorities. The Level class extends the Priority class to be conform with java.util.logging. For the standard levels, we have DEBUG < INFO < WARN < ERROR < FATAL.

==Layout==
The layout is defined in a pattern prefixed by % and a following letter code:

* c: category
* C: class name
* d{<Format>}: date e.g. %d{HH:mm:ss,SSS}
* E: exception stack
* F: file name
* l: location
* L: line number
* m: message
* M: method name
* p: log level (ERR, INFO, ...)
* s: message
* t: name of the thread

==Logging==
Das Loggen von Meldungen erfolgt über so genannte "Printing-Methods". Folgende Methoden sind verfügbar: 
 logger.[debug()|info()|warn()|error()fatal()|log()|trace()];

=Configuration=
Properties can be defined by a properties file or by an XML file. The xml configuration class offers more flexibility and the benefits, and drawbacks, of an XML based configuration.

Logging Level are:
* ALL
* DEBUG
* ERROR
* FATAL
* INFO
* OFF
* TRACE
* WARN