    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    }