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 */
017package org.apache.logging.log4j.core.lookup;
018
019import org.apache.logging.log4j.Logger;
020import org.apache.logging.log4j.Marker;
021import org.apache.logging.log4j.MarkerManager;
022import org.apache.logging.log4j.core.LogEvent;
023import org.apache.logging.log4j.core.config.plugins.Plugin;
024import org.apache.logging.log4j.status.StatusLogger;
025
026/**
027 * Looks up keys from system properties.
028 */
029@Plugin(name = "sys", category = StrLookup.CATEGORY)
030public 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}