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.logging.log4j.core.appender.rewrite;
018
019import java.util.concurrent.ConcurrentHashMap;
020import java.util.concurrent.ConcurrentMap;
021
022import org.apache.logging.log4j.core.Appender;
023import org.apache.logging.log4j.core.Filter;
024import org.apache.logging.log4j.core.LogEvent;
025import org.apache.logging.log4j.core.appender.AbstractAppender;
026import org.apache.logging.log4j.core.config.AppenderControl;
027import org.apache.logging.log4j.core.config.AppenderRef;
028import org.apache.logging.log4j.core.config.Configuration;
029import org.apache.logging.log4j.core.config.plugins.Plugin;
030import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
031import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
032import org.apache.logging.log4j.core.config.plugins.PluginElement;
033import org.apache.logging.log4j.core.config.plugins.PluginFactory;
034import org.apache.logging.log4j.core.util.Booleans;
035
036/**
037 * This Appender allows the logging event to be manipulated before it is processed by other Appenders.
038 */
039@Plugin(name = "Rewrite", category = "Core", elementType = "appender", printObject = true)
040public final class RewriteAppender extends AbstractAppender {
041    
042    private static final long serialVersionUID = 1L;
043
044    private final Configuration config;
045    private final ConcurrentMap<String, AppenderControl> appenders = new ConcurrentHashMap<>();
046    private final RewritePolicy rewritePolicy;
047    private final AppenderRef[] appenderRefs;
048
049    private RewriteAppender(final String name, final Filter filter, final boolean ignoreExceptions,
050                            final AppenderRef[] appenderRefs, final RewritePolicy rewritePolicy,
051                            final Configuration config) {
052        super(name, filter, null, ignoreExceptions);
053        this.config = config;
054        this.rewritePolicy = rewritePolicy;
055        this.appenderRefs = appenderRefs;
056    }
057
058    @Override
059    public void start() {
060        for (final AppenderRef ref : appenderRefs) {
061            final String name = ref.getRef();
062            final Appender appender = config.getAppender(name);
063            if (appender != null) {
064                final Filter filter = appender instanceof AbstractAppender ?
065                    ((AbstractAppender) appender).getFilter() : null;
066                appenders.put(name, new AppenderControl(appender, ref.getLevel(), filter));
067            } else {
068                LOGGER.error("Appender " + ref + " cannot be located. Reference ignored");
069            }
070        }
071        super.start();
072    }
073
074    @Override
075    public void stop() {
076        super.stop();
077    }
078
079    /**
080     * Modifies the event and pass to the subordinate Appenders.
081     * @param event The LogEvent.
082     */
083    @Override
084    public void append(LogEvent event) {
085        if (rewritePolicy != null) {
086            event = rewritePolicy.rewrite(event);
087        }
088        for (final AppenderControl control : appenders.values()) {
089            control.callAppender(event);
090        }
091    }
092
093    /**
094     * Creates a RewriteAppender.
095     * @param name The name of the Appender.
096     * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
097     *               they are propagated to the caller.
098     * @param appenderRefs An array of Appender names to call.
099     * @param config The Configuration.
100     * @param rewritePolicy The policy to use to modify the event.
101     * @param filter A Filter to filter events.
102     * @return The created RewriteAppender.
103     */
104    @PluginFactory
105    public static RewriteAppender createAppender(
106            @PluginAttribute("name") final String name,
107            @PluginAttribute("ignoreExceptions") final String ignore,
108            @PluginElement("AppenderRef") final AppenderRef[] appenderRefs,
109            @PluginConfiguration final Configuration config,
110            @PluginElement("RewritePolicy") final RewritePolicy rewritePolicy,
111            @PluginElement("Filter") final Filter filter) {
112
113        final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
114        if (name == null) {
115            LOGGER.error("No name provided for RewriteAppender");
116            return null;
117        }
118        if (appenderRefs == null) {
119            LOGGER.error("No appender references defined for RewriteAppender");
120            return null;
121        }
122        return new RewriteAppender(name, filter, ignoreExceptions, appenderRefs, rewritePolicy, config);
123    }
124}