Log4j

Concepts

Log4j has four fundamental objects: categories, priorities (levels), appenders and layouts.

Category

A category is a like java named entity. There exists a special root category that simply is, but has no name.

Priority

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.

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