What are the features of log4j?

Michael Canzoneri

  • log4j is optimized for speed.
  • log4j is based on a named logger hierarchy.
  • log4j is fail-stop but not reliable.
  • log4j is thread-safe.
  • log4j is not restricted to a predefined set of facilities.
  • Logging behavior can be set at runtime using a configuration file. Configuration files can be property files or in XML format.
  • log4j is designed to handle Java Exceptions from the start.
  • log4j can direct its output to a file, the console, an java.io.OutputStream, java.io.Writer, a remote server using TCP, a remote Unix Syslog daemon, to a remote listener using JMS, to the NT EventLog or even send e-mail.
  • log4j uses 5 levels, namely DEBUG, INFO, WARN, ERROR and FATAL.
  • The format of the log output can be easily changed by extending the Layout class.
  • The target of the log output as well as the writing strategy can be altered by implementations of the Appender interface.
  • log4j supports multiple output appenders per logger.
  • log4j supports internationalization.