Log4j: Difference between revisions
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==Logger== | ==Logger== | ||
Loggers are named entities. 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. | Loggers are named entities. 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: | The '''root logger''' resides at the top of the logger hierarchy. It is exceptional in two ways: | ||
#it always exists, | #it always exists, | ||
Revision as of 15:54, 29 January 2012
Concepts
Log4j has teh following fundamental objects:
- logger
- categories,
- priorities (levels),
- appenders and
- layouts.
Logger
Loggers are named entities. 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.
Category
A category is a like java named entity. There exists a special root category that simply is, but has no name.
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