    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    }