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.util;
018
019import java.util.Objects;
020import java.util.Properties;
021
022/**
023 * PropertySource backed by the current system properties. Other than having a
024 * higher priority over normal properties, this follows the same rules as
025 * {@link PropertiesPropertySource}.
026 *
027 * @since 2.10.0
028 */
029public class SystemPropertiesPropertySource implements PropertySource {
030
031        private static final int DEFAULT_PRIORITY = 100;
032        private static final String PREFIX = "log4j2.";
033
034        @Override
035        public int getPriority() {
036                return DEFAULT_PRIORITY;
037        }
038
039        @Override
040        public void forEach(final BiConsumer<String, String> action) {
041                Properties properties;
042                try {
043                        properties = System.getProperties();
044                } catch (final SecurityException e) {
045                        // (1) There is no status logger.
046                        // (2) LowLevelLogUtil also consults system properties ("line.separator") to
047                        // open a BufferedWriter, so this may fail as well. Just having a hard reference
048                        // in this code to LowLevelLogUtil would cause a problem.
049                        // (3) We could log to System.err (nah) or just be quiet as we do now.
050                        return;
051                }
052                // Lock properties only long enough to get a thread-safe SAFE snapshot of its
053                // current keys, an array.
054                final Object[] keySet;
055                synchronized (properties) {
056                        keySet = properties.keySet().toArray();
057                }
058                // Then traverse for an unknown amount of time.
059                // Some keys may now be absent, in which case, the value is null.
060                for (final Object key : keySet) {
061                        final String keyStr = Objects.toString(key, null);
062                        action.accept(keyStr, properties.getProperty(keyStr));
063                }
064        }
065
066        @Override
067        public CharSequence getNormalForm(final Iterable<? extends CharSequence> tokens) {
068                return PREFIX + Util.joinAsCamelCase(tokens);
069        }
070
071}