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 java.util.Map;
020
021import org.apache.logging.log4j.core.LogEvent;
022import org.apache.logging.log4j.core.config.plugins.Plugin;
023import org.apache.logging.log4j.message.MapMessage;
024
025/**
026 * The basis for a lookup based on a Map.
027 */
028@Plugin(name = "map", category = "Lookup")
029public class MapLookup implements StrLookup {
030    /**
031     * Map keys are variable names and value.
032     */
033    private final Map<String, String> map;
034
035    /**
036     * Creates a new instance backed by a Map. Used by the default lookup.
037     *
038     * @param map the map of keys to values, may be null
039     */
040    public MapLookup(final Map<String, String> map) {
041        this.map = map;
042    }
043
044    /**
045     * Constructor when used directly as a plugin.
046     */
047    public MapLookup() {
048        this.map = null;
049    }
050
051    /**
052     * Looks up a String key to a String value using the map.
053     * <p/>
054     * If the map is null, then null is returned.
055     * The map result object is converted to a string using toString().
056     *
057     * @param key the key to be looked up, may be null
058     * @return the matching value, null if no match
059     */
060    @Override
061    public String lookup(final String key) {
062        if (map == null) {
063            return null;
064        }
065        final String obj = map.get(key);
066        if (obj == null) {
067            return null;
068        }
069        return obj;
070    }
071
072    @Override
073    public String lookup(final LogEvent event, final String key) {
074        if (map == null && !(event.getMessage() instanceof MapMessage)) {
075            return null;
076        }
077        if (map != null && map.containsKey(key)) {
078            final String obj = map.get(key);
079            if (obj != null) {
080                return obj;
081            }
082        }
083        if (event.getMessage() instanceof MapMessage) {
084            return ((MapMessage) event.getMessage()).get(key);
085        }
086        return null;
087    }
088}