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.io.Serializable;
20 import java.util.ArrayList;
21 import java.util.List;
22 import java.util.Map;
23 import java.util.Objects;
24 import java.util.concurrent.ConcurrentHashMap;
25 import java.util.regex.Matcher;
26 import java.util.regex.Pattern;
27
28 /**
29 * A source for global configuration properties.
30 *
31 * @since 2.10.0
32 */
33 public interface PropertySource {
34
35 /**
36 * Returns the order in which this PropertySource has priority. A higher value means that the source will be
37 * applied later so as to take precedence over other property sources.
38 *
39 * @return priority value
40 */
41 int getPriority();
42
43 /**
44 * Iterates over all properties and performs an action for each key/value pair.
45 *
46 * @param action action to perform on each key/value pair
47 */
48 void forEach(BiConsumer<String, String> action);
49
50 /**
51 * Converts a list of property name tokens into a normal form. For example, a list of tokens such as
52 * "foo", "bar", "baz", might be normalized into the property name "log4j2.fooBarBaz".
53 *
54 * @param tokens list of property name tokens
55 * @return a normalized property name using the given tokens
56 */
57 CharSequence getNormalForm(Iterable<? extends CharSequence> tokens);
58
59 /**
60 * Comparator for ordering PropertySource instances by priority.
61 *
62 * @since 2.10.0
63 */
64 class Comparator implements java.util.Comparator<PropertySource>, Serializable {
65 private static final long serialVersionUID = 1L;
66
67 @Override
68 public int compare(final PropertySource o1, final PropertySource o2) {
69 return Integer.compare(Objects.requireNonNull(o1).getPriority(), Objects.requireNonNull(o2).getPriority());
70 }
71 }
72
73 /**
74 * Utility methods useful for PropertySource implementations.
75 *
76 * @since 2.10.0
77 */
78 final class Util {
79 private static final String PREFIXES = "(?i:^log4j2?[-._/]?|^org\\.apache\\.logging\\.log4j\\.)?";
80 private static final Pattern PROPERTY_TOKENIZER = Pattern.compile(PREFIXES + "([A-Z]*[a-z0-9]+|[A-Z0-9]+)[-._/]?");
81 private static final Map<CharSequence, List<CharSequence>> CACHE = new ConcurrentHashMap<>();
82
83 /**
84 * Converts a property name string into a list of tokens. This will strip a prefix of {@code log4j},
85 * {@code log4j2}, {@code Log4j}, or {@code org.apache.logging.log4j}, along with separators of
86 * dash {@code -}, dot {@code .}, underscore {@code _}, and slash {@code /}. Tokens can also be separated
87 * by camel case conventions without needing a separator character in between.
88 *
89 * @param value property name
90 * @return the property broken into lower case tokens
91 */
92 public static List<CharSequence> tokenize(final CharSequence value) {
93 if (CACHE.containsKey(value)) {
94 return CACHE.get(value);
95 }
96 final List<CharSequence> tokens = new ArrayList<>();
97 final Matcher matcher = PROPERTY_TOKENIZER.matcher(value);
98 while (matcher.find()) {
99 tokens.add(matcher.group(1).toLowerCase());
100 }
101 CACHE.put(value, tokens);
102 return tokens;
103 }
104
105 /**
106 * Joins a list of strings using camelCaseConventions.
107 *
108 * @param tokens tokens to convert
109 * @return tokensAsCamelCase
110 */
111 public static CharSequence joinAsCamelCase(final Iterable<? extends CharSequence> tokens) {
112 final StringBuilder sb = new StringBuilder();
113 boolean first = true;
114 for (final CharSequence token : tokens) {
115 if (first) {
116 sb.append(token);
117 } else {
118 sb.append(Character.toUpperCase(token.charAt(0)));
119 if (token.length() > 1) {
120 sb.append(token.subSequence(1, token.length()));
121 }
122 }
123 first = false;
124 }
125 return sb.toString();
126 }
127
128 private Util() {
129 }
130 }
131 }