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Filter.java API Doc Apache log4j 1.2.15 4181 Sat Aug 25 00:09:40 BST 2007 org.apache.log4j.spi

Filter

java.lang.Object

public abstract class Filter extends Object implements OptionHandler

Users should extend this class to implement customized logging event filtering. Note that {@link org.apache.log4j.Category} and {@link org.apache.log4j.AppenderSkeleton}, the parent class of all standard appenders, 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 {@link #decide decide(LoggingEvent)} method of each filter is called sequentially, in the order of their addition to the chain.

The {@link #decide decide(LoggingEvent)} method must return one of the integer constants {@link #DENY}, {@link #NEUTRAL} or {@link #ACCEPT}.

If the value {@link #DENY} is returned, then the log event is dropped immediately without consulting with the remaining filters.

If the value {@link #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 {@link #ACCEPT} is returned, then the log event is logged without consulting the remaining filters.

The philosophy of log4j filters is largely inspired from the Linux ipchains.

Note that filtering is only supported by the {@link org.apache.log4j.xml.DOMConfigurator DOMConfigurator}. The {@link org.apache.log4j.PropertyConfigurator PropertyConfigurator} does not support filters.

author: Ceki Gülcü
since: 0.9.0

Fields Summary
public Filter
next
Points to the next filter in the filter chain.
public static final int
DENY
The log event must be dropped immediately without consulting with the remaining filters, if any, in the chain.
public static final int
NEUTRAL
This filter is neutral with respect to the log event. The remaining filters, if any, should be consulted for a final decision.
public static final int
ACCEPT
The log event must be logged immediately without consulting with the remaining filters, if any, in the chain.
Constructors Summary
Methods Summary
public void activateOptions()
Usually filters options become active when set. We provide a default do-nothing implementation for convenience.
public abstract int decide(org.apache.log4j.spi.LoggingEvent event)
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.
param
event The LoggingEvent to decide upon.
return
decision The decision of the filter.
public org.apache.log4j.spi.Filter getNext()
Return the pointer to the next filter;
return next;
public void setNext(org.apache.log4j.spi.Filter next)
Set the next filter pointer.
this.next = next;