org.apache.log4j.spi
Interfaces 
AppenderAttachable
Configurator
ErrorCode
ErrorHandler
HierarchyEventListener
LoggerFactory
LoggerRepository
OptionHandler
RendererSupport
RepositorySelector
ThrowableRenderer
ThrowableRendererSupport
TriggeringEventEvaluator
Classes 
DefaultRepositorySelector
Filter
LocationInfo
LoggingEvent
NOPLogger
NOPLoggerRepository
RootCategory
RootLogger
ThrowableInformation