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