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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  package org.apache.logging.log4j.util;
18  
19  import java.util.Map;
20  
21  /**
22   * PropertySource implementation that uses environment variables as a source. All environment variables must begin
23   * with {@code LOG4J_} so as not to conflict with other variables. Normalized environment variables follow a scheme
24   * like this: {@code log4j2.fooBarProperty} would normalize to {@code LOG4J_FOO_BAR_PROPERTY}.
25   *
26   * @since 2.10.0
27   */
28  public class EnvironmentPropertySource implements PropertySource {
29      @Override
30      public int getPriority() {
31          return -100;
32      }
33  
34      @Override
35      public void forEach(final BiConsumer<String, String> action) {
36          for (final Map.Entry<String, String> entry : System.getenv().entrySet()) {
37              final String key = entry.getKey();
38              if (key.startsWith("LOG4J_")) {
39                  action.accept(key.substring(6), entry.getValue());
40              }
41          }
42      }
43  
44      @Override
45      public CharSequence getNormalForm(final Iterable<? extends CharSequence> tokens) {
46          final StringBuilder sb = new StringBuilder("LOG4J");
47          for (final CharSequence token : tokens) {
48              sb.append('_');
49              for (int i = 0; i < token.length(); i++) {
50                  sb.append(Character.toUpperCase(token.charAt(i)));
51              }
52          }
53          return sb.toString();
54      }
55  }