Users should extend this class to implement customized logging event filtering. Note that log4cpp::Category and lof4cpp::Appender have built-in filtering rules. It is suggested that you first use and understand the built-in rules before rushing to write your own custom filters.
This abstract class assumes and also imposes that filters be organized in a linear chain. The
decide(LoggingEvent) method of each filter is called sequentially, in the order of their addition to the chain.
decide(LoggingEvent) method must return a Decision value, either DENY, NEUTRAL or ACCCEPT.
If the value DENY is returned, then the log event is dropped immediately without consulting with the remaining filters.
If the value NEUTRAL is returned, then the next filter in the chain is consulted. If there are no more filters in the chain, then the log event is logged. Thus, in the presence of no filters, the default behaviour is to log all logging events.
If the value ACCEPT is returned, then the log event is logged without consulting the remaining filters.
The philosophy of log4cpp filters is largely inspired from the Linux ipchains.
Definition at line 49 of file Filter.hh.