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.core.LogEvent;
020import org.apache.logging.log4j.core.config.plugins.Plugin;
021
022/**
023 * Looks up keys from environment variables.
024 */
025@Plugin(name = "env", category = "Lookup")
026public class EnvironmentLookup implements StrLookup {
027
028    /**
029     * Looks up the value of the environment variable.
030     * @param key  the key to be looked up, may be null
031     * @return The value of the environment variable.
032     */
033    @Override
034    public String lookup(final String key) {
035        return System.getenv(key);
036    }
037
038    /**
039     * Looks up the value of the environment variable.
040     * @param event The current LogEvent (is ignored by this StrLookup).
041     * @param key  the key to be looked up, may be null
042     * @return The value of the environment variable.
043     */
044    @Override
045    public String lookup(final LogEvent event, final String key) {
046        return System.getenv(key);
047    }
048}