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# log4cplus::spi::Filter Class Reference

Users should extend this class to implement customized logging event filtering. More...

`#include <filter.h>`

Inheritance diagram for log4cplus::spi::Filter:

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Collaboration diagram for log4cplus::spi::Filter:

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List of all members.

## Public Member Functions
| Filter ()
virtual | ~Filter ()
void | appendFilter (FilterPtr filter)
| Appends `filter` to the end of this filter chain.
virtual FilterResult | decide (const InternalLoggingEvent &event) const=0
## Public Attributes
FilterPtr | next
| Points to the next filter in the filter chain.

## Detailed Description

Users should extend this class to implement customized logging event filtering.

Note that the Logger and Appender classes 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.

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 log4cplus filters is largely inspired from the Linux ipchains.

Definition at line 84 of file filter.h.

## Constructor & Destructor Documentation

log4cplus::spi::Filter::Filter | ( |  | ) |

virtual log4cplus::spi::Filter::~Filter | ( |  | ) | `[virtual]`

## Member Function Documentation

void log4cplus::spi::Filter::appendFilter | ( | FilterPtr | filter | ) |

| Appends `filter` to the end of this filter chain.

virtual FilterResult log4cplus::spi::Filter::decide | ( | const InternalLoggingEvent & | event | ) | const`[pure virtual]`

  | If the decision is `DENY`, then the event will be dropped. If the decision is `NEUTRAL`, then the next filter, if any, will be invoked. If the decision is ACCEPT then the event will be logged without consulting with other filters in the chain. Parameters:
  event | The LoggingEvent to decide upon.
  decision | The decision of the filter.
Implemented in log4cplus::spi::DenyAllFilter, log4cplus::spi::LogLevelMatchFilter, log4cplus::spi::LogLevelRangeFilter, and log4cplus::spi::StringMatchFilter.

## Member Data Documentation

FilterPtr log4cplus::spi::Filter::next

| Points to the next filter in the filter chain. Definition at line 112 of file filter.h.

The documentation for this class was generated from the following file:

- filter.h