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     */
017    package org.apache.logging.log4j.core.appender.rewrite;
018    
019    import java.util.Map;
020    import java.util.concurrent.ConcurrentHashMap;
021    import java.util.concurrent.ConcurrentMap;
022    
023    import org.apache.logging.log4j.core.Appender;
024    import org.apache.logging.log4j.core.Filter;
025    import org.apache.logging.log4j.core.LogEvent;
026    import org.apache.logging.log4j.core.appender.AbstractAppender;
027    import org.apache.logging.log4j.core.config.AppenderControl;
028    import org.apache.logging.log4j.core.config.AppenderRef;
029    import org.apache.logging.log4j.core.config.Configuration;
030    import org.apache.logging.log4j.core.config.plugins.Plugin;
031    import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
032    import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
033    import org.apache.logging.log4j.core.config.plugins.PluginElement;
034    import org.apache.logging.log4j.core.config.plugins.PluginFactory;
035    import org.apache.logging.log4j.core.util.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)
041    public 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            for (final AppenderRef ref : appenderRefs) {
059                final String name = ref.getRef();
060                final Appender appender = config.getAppender(name);
061                if (appender != null) {
062                    final Filter filter = appender instanceof AbstractAppender ?
063                        ((AbstractAppender) appender).getFilter() : null;
064                    appenders.put(name, new AppenderControl(appender, ref.getLevel(), filter));
065                } else {
066                    LOGGER.error("Appender " + ref + " cannot be located. Reference ignored");
067                }
068            }
069            super.start();
070        }
071    
072        @Override
073        public void stop() {
074            super.stop();
075        }
076    
077        /**
078         * Modify the event and pass to the subordinate Appenders.
079         * @param event The LogEvent.
080         */
081        @Override
082        public void append(LogEvent event) {
083            if (rewritePolicy != null) {
084                event = rewritePolicy.rewrite(event);
085            }
086            for (final AppenderControl control : appenders.values()) {
087                control.callAppender(event);
088            }
089        }
090    
091        /**
092         * Create a RewriteAppender.
093         * @param name The name of the Appender.
094         * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
095         *               they are propagated to the caller.
096         * @param appenderRefs An array of Appender names to call.
097         * @param config The Configuration.
098         * @param rewritePolicy The policy to use to modify the event.
099         * @param filter A Filter to filter events.
100         * @return The created RewriteAppender.
101         */
102        @PluginFactory
103        public static RewriteAppender createAppender(
104                @PluginAttribute("name") final String name,
105                @PluginAttribute("ignoreExceptions") final String ignore,
106                @PluginElement("AppenderRef") final AppenderRef[] appenderRefs,
107                @PluginConfiguration final Configuration config,
108                @PluginElement("RewritePolicy") final RewritePolicy rewritePolicy,
109                @PluginElement("Filter") final Filter filter) {
110    
111            final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
112            if (name == null) {
113                LOGGER.error("No name provided for RewriteAppender");
114                return null;
115            }
116            if (appenderRefs == null) {
117                LOGGER.error("No appender references defined for RewriteAppender");
118                return null;
119            }
120            return new RewriteAppender(name, filter, ignoreExceptions, appenderRefs, rewritePolicy, config);
121        }
122    }