org.apache.log4j.spi: abstract public class: Filter

org.apache.log4j.spi
abstract public class: Filter [javadoc | source]

java.lang.Object
   org.apache.log4j.spi.Filter

All Implemented Interfaces:
OptionHandler

Direct Known Subclasses:
LevelMatchFilter, DenyAllFilter, LevelRangeFilter, StringMatchFilter

Users should extend this class to implement customized logging event filtering. Note that org.apache.log4j.Category and 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 decide(LoggingEvent) method of each filter is called sequentially, in the order of their addition to the chain.

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

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 log4j filters is largely inspired from the Linux ipchains.

Note that filtering is only supported by the DOMConfigurator . The PropertyConfigurator does not support filters.

author: Ceki - Gülcü

since: 0.9.0 -

Field 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.

Method from org.apache.log4j.spi.Filter Summary:
activateOptions, decide, getNext, setNext

Methods from java.lang.Object:
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from org.apache.log4j.spi.Filter Detail:
public void activateOptions() { } Usually filters options become active when set. We provide a default do-nothing implementation for convenience.
abstract public int decide(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.
public Filter getNext() { return next; } Return the pointer to the next filter;
public void setNext(Filter next) { this.next = next; } Set the next filter pointer.

Method from org.apache.log4j.spi.Filter Detail:

 public  void activateOptions() {

}

Usually filters options become active when set. We provide a default do-nothing implementation for convenience.

 abstract public int decide(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.

 public Filter getNext() {
        return next;
}

Return the pointer to the next filter;

 public  void setNext(Filter next) {
    this.next = next;
}

Set the next filter pointer.