Class Filter

java.lang.Object
org.apache.log4j.spi.Filter
All Implemented Interfaces:
OptionHandler
Direct Known Subclasses:
DenyAllFilter, LevelMatchFilter, LevelRangeFilter, StringMatchFilter

public abstract class Filter extends Object implements OptionHandler
Users should extend this class to implement customized logging event filtering. Note that Category and 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.

Since:
0.9.0
Author:
Ceki Gülcü
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    The log event must be logged immediately without consulting with the remaining filters, if any, in the chain.
    static final int
    The log event must be dropped immediately without consulting with the remaining filters, if any, in the chain.
    static final int
    This filter is neutral with respect to the log event.
    Deprecated.
    As of 1.2.12, use getNext() and setNext(org.apache.log4j.spi.Filter) instead
  • Constructor Summary

    Constructors
    Constructor
    Description
     
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Usually filters options become active when set.
    abstract int
    If the decision is DENY, then the event will be dropped.
    Return the pointer to the next filter;
    void
    Set the next filter pointer.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • next

      public Filter next
      Deprecated.
      As of 1.2.12, use getNext() and setNext(org.apache.log4j.spi.Filter) instead
      Points to the next filter in the filter chain.
    • DENY

      public static final int DENY
      The log event must be dropped immediately without consulting with the remaining filters, if any, in the chain.
      See Also:
    • NEUTRAL

      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.
      See Also:
    • ACCEPT

      public static final int ACCEPT
      The log event must be logged immediately without consulting with the remaining filters, if any, in the chain.
      See Also:
  • Constructor Details

    • Filter

      public Filter()
  • Method Details

    • activateOptions

      public void activateOptions()
      Usually filters options become active when set. We provide a default do-nothing implementation for convenience.
      Specified by:
      activateOptions in interface OptionHandler
    • decide

      public abstract 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.

      Parameters:
      event - The LoggingEvent to decide upon.
      Returns:
      decision The decision of the filter.
    • setNext

      public void setNext(Filter next)
      Set the next filter pointer.
    • getNext

      public Filter getNext()
      Return the pointer to the next filter;