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 default void forEach(BiConsumer<String, String> action) {
49 }
50
51 /**
52 * Converts a list of property name tokens into a normal form. For example, a list of tokens such as
53 * "foo", "bar", "baz", might be normalized into the property name "log4j2.fooBarBaz".
54 *
55 * @param tokens list of property name tokens
56 * @return a normalized property name using the given tokens
57 */
58 default CharSequence getNormalForm(Iterable<? extends CharSequence> tokens) {
59 return null;
60 }
61
62 /**
63 * For PropertySources that cannot iterate over all the potential properties this provides a direct lookup.
64 * @param key The key to search for.
65 * @return The value or null;
66 * @since 2.13.0
67 */
68 default String getProperty(String key) {
69 return null;
70 }
71
72
73 /**
74 * For PropertySources that cannot iterate over all the potential properties this provides a direct lookup.
75 * @param key The key to search for.
76 * @return The value or null;
77 * @since 2.13.0
78 */
79 default boolean containsProperty(String key) {
80 return false;
81 }
82
83 /**
84 * Comparator for ordering PropertySource instances by priority.
85 *
86 * @since 2.10.0
87 */
88 class Comparator implements java.util.Comparator<PropertySource>, Serializable {
89 private static final long serialVersionUID = 1L;
90
91 @Override
92 public int compare(final PropertySource o1, final PropertySource o2) {
93 return Integer.compare(Objects.requireNonNull(o1).getPriority(), Objects.requireNonNull(o2).getPriority());
94 }
95 }
96
97 /**
98 * Utility methods useful for PropertySource implementations.
99 *
100 * @since 2.10.0
101 */
102 final class Util {
103 private static final String PREFIXES = "(?i:^log4j2?[-._/]?|^org\\.apache\\.logging\\.log4j\\.)?";
104 private static final Pattern PROPERTY_TOKENIZER = Pattern.compile(PREFIXES + "([A-Z]*[a-z0-9]+|[A-Z0-9]+)[-._/]?");
105 private static final Map<CharSequence, List<CharSequence>> CACHE = new ConcurrentHashMap<>();
106
107 /**
108 * Converts a property name string into a list of tokens. This will strip a prefix of {@code log4j},
109 * {@code log4j2}, {@code Log4j}, or {@code org.apache.logging.log4j}, along with separators of
110 * dash {@code -}, dot {@code .}, underscore {@code _}, and slash {@code /}. Tokens can also be separated
111 * by camel case conventions without needing a separator character in between.
112 *
113 * @param value property name
114 * @return the property broken into lower case tokens
115 */
116 public static List<CharSequence> tokenize(final CharSequence value) {
117 if (CACHE.containsKey(value)) {
118 return CACHE.get(value);
119 }
120 final List<CharSequence> tokens = new ArrayList<>();
121 final Matcher matcher = PROPERTY_TOKENIZER.matcher(value);
122 while (matcher.find()) {
123 tokens.add(matcher.group(1).toLowerCase());
124 }
125 CACHE.put(value, tokens);
126 return tokens;
127 }
128
129 /**
130 * Joins a list of strings using camelCaseConventions.
131 *
132 * @param tokens tokens to convert
133 * @return tokensAsCamelCase
134 */
135 public static CharSequence joinAsCamelCase(final Iterable<? extends CharSequence> tokens) {
136 final StringBuilder sb = new StringBuilder();
137 boolean first = true;
138 for (final CharSequence token : tokens) {
139 if (first) {
140 sb.append(token);
141 } else {
142 sb.append(Character.toUpperCase(token.charAt(0)));
143 if (token.length() > 1) {
144 sb.append(token.subSequence(1, token.length()));
145 }
146 }
147 first = false;
148 }
149 return sb.toString();
150 }
151
152 private Util() {
153 }
154 }
155 }