Log4j Version 1.2.7: Package org.apache.log4j.spi org.apache.log4j.spi
Interfaces 
AppenderAttachable
Configurator
ErrorCode
ErrorHandler
HierarchyEventListener
LoggerFactory
LoggerRepository
OptionHandler
RendererSupport
RepositorySelector
TriggeringEventEvaluator
Classes 
DefaultRepositorySelector
Filter
LocationInfo
LoggingEvent
RootCategory
ThrowableInformation