Contains part of the System Programming Interface (SPI) needed to extend log4j.


AppenderAttachable Interface for attaching appenders to objects. 
Configurator Implemented by classes capable of configuring log4j using a URL. 
ErrorCode This interface defines commonly encoutered error codes. 
ErrorHandler Appenders may delegate their error handling to ErrorHandlers
HierarchyEventListener Listen to events occuring within a Hierarchy
LoggerFactory Implement this interface to create new instances of Logger or a sub-class of Logger. 
LoggerRepository A LoggerRepository is used to create and retrieve Loggers
OptionHandler A string based interface to configure package components. 
RepositorySelector The LogManager uses one (and only one) RepositorySelector implementation to select the LoggerRepository for a particular application context. 
ThrowableRenderer Implemented by classes that render instances of java.lang.Throwable (exceptions and errors) into a string representation. 
ThrowableRendererSupport Implemented by logger repositories that support configurable rendering of Throwables. 
TriggeringEventEvaluator Implementions of this interface allow certain appenders to decide when to perform an appender specific action. 


Filter Users should extend this class to implement customized logging event filtering. 
LocationInfo The internal representation of caller location information. 
LoggingEvent The internal representation of logging events. 
NOPLogger No-operation implementation of Logger used by NOPLoggerRepository. 
NOPLoggerRepository No-operation implementation of LoggerRepository which is used when LogManager.repositorySelector is erroneously nulled during class reloading. 
RootCategory This class is deprecated. Replaced by RootLogger.  
RootLogger RootLogger sits at the top of the logger hierachy. 
ThrowableInformation ThrowableInformation is log4j's internal representation of throwables.