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.Map;
020
021/**
022 * PropertySource implementation that uses environment variables as a source. All environment variables must begin
023 * with {@code LOG4J_} so as not to conflict with other variables. Normalized environment variables follow a scheme
024 * like this: {@code log4j2.fooBarProperty} would normalize to {@code LOG4J_FOO_BAR_PROPERTY}.
025 *
026 * @since 2.10.0
027 */
028public class EnvironmentPropertySource implements PropertySource {
029    @Override
030    public int getPriority() {
031        return -100;
032    }
033
034    @Override
035    public void forEach(final BiConsumer<String, String> action) {
036        for (final Map.Entry<String, String> entry : System.getenv().entrySet()) {
037            final String key = entry.getKey();
038            if (key.startsWith("LOG4J_")) {
039                action.accept(key.substring(6), entry.getValue());
040            }
041        }
042    }
043
044    @Override
045    public CharSequence getNormalForm(final Iterable<? extends CharSequence> tokens) {
046        final StringBuilder sb = new StringBuilder("LOG4J");
047        for (final CharSequence token : tokens) {
048            sb.append('_');
049            for (int i = 0; i < token.length(); i++) {
050                sb.append(Character.toUpperCase(token.charAt(i)));
051            }
052        }
053        return sb.toString();
054    }
055}