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.concurrent.ConcurrentHashMap;
020    import java.util.concurrent.ConcurrentMap;
021    
022    import org.apache.logging.log4j.core.Appender;
023    import org.apache.logging.log4j.core.Filter;
024    import org.apache.logging.log4j.core.LogEvent;
025    import org.apache.logging.log4j.core.appender.AbstractAppender;
026    import org.apache.logging.log4j.core.config.AppenderControl;
027    import org.apache.logging.log4j.core.config.AppenderRef;
028    import org.apache.logging.log4j.core.config.Configuration;
029    import org.apache.logging.log4j.core.config.plugins.Plugin;
030    import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
031    import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
032    import org.apache.logging.log4j.core.config.plugins.PluginElement;
033    import org.apache.logging.log4j.core.config.plugins.PluginFactory;
034    import 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)
040    public 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<String, AppenderControl>();
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         * Modify 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         * Create 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    }