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