001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.log4j.spi;
018
019/**
020 * @since 0.9.0
021 */
022public abstract class Filter {
023
024    /**
025     * The log event must be dropped immediately without consulting
026     * with the remaining filters, if any, in the chain.
027     */
028    public static final int DENY = -1;
029
030    /**
031     * This filter is neutral with respect to the log event. The
032     * remaining filters, if any, should be consulted for a final decision.
033     */
034    public static final int NEUTRAL = 0;
035
036    /**
037     * The log event must be logged immediately without consulting with
038     * the remaining filters, if any, in the chain.
039     */
040    public static final int ACCEPT = 1;
041
042    /**
043     * Points to the next filter in the filter chain.
044     *
045     * @deprecated As of 1.2.12, use {@link #getNext} and {@link #setNext} instead
046     */
047    @Deprecated
048    public Filter next;
049
050    /**
051     * Usually filters options become active when set. We provide a
052     * default do-nothing implementation for convenience.
053     */
054    public void activateOptions() {
055    }
056
057
058    /**
059     * <p>If the decision is <code>DENY</code>, then the event will be
060     * dropped. If the decision is <code>NEUTRAL</code>, then the next
061     * filter, if any, will be invoked. If the decision is ACCEPT then
062     * the event will be logged without consulting with other filters in
063     * the chain.
064     *
065     * @param event The LoggingEvent to decide upon.
066     * @return decision The decision of the filter.
067     */
068    public abstract int decide(LoggingEvent event);
069
070    /**
071     * Set the next filter pointer.
072     * @param next The next Filter.
073     */
074    public void setNext(final Filter next) {
075        this.next = next;
076    }
077
078    /**
079     * Return the pointer to the next filter.
080     * @return The next Filter.
081     */
082    public Filter getNext() {
083        return next;
084    }
085
086}