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.lookup;
018    
019    import org.apache.logging.log4j.Logger;
020    import org.apache.logging.log4j.Marker;
021    import org.apache.logging.log4j.MarkerManager;
022    import org.apache.logging.log4j.core.LogEvent;
023    import org.apache.logging.log4j.core.config.plugins.Plugin;
024    import org.apache.logging.log4j.status.StatusLogger;
025    
026    /**
027     * Looks up keys from system properties.
028     */
029    @Plugin(name = "sys", category = StrLookup.CATEGORY)
030    public class SystemPropertiesLookup extends AbstractLookup {
031    
032        private static final Logger LOGGER = StatusLogger.getLogger();
033        private static final Marker LOOKUP = MarkerManager.getMarker("LOOKUP");
034    
035        /**
036         * Looks up the value for the key using the data in the LogEvent.
037         * @param event The current LogEvent.
038         * @param key  the key to be looked up, may be null
039         * @return The value associated with the key.
040         */
041        @Override
042        public String lookup(final LogEvent event, final String key) {
043            try {
044                return System.getProperty(key);
045            } catch (final Exception ex) {
046                LOGGER.warn(LOOKUP, "Error while getting system property [{}].", key, ex);
047                return null;
048            }
049        }
050    }