1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2024 the original author or authors.
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ///////////////////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle;
21
22 import java.util.Map;
23 import java.util.Properties;
24 import java.util.function.Function;
25 import java.util.stream.Collectors;
26
27 /**
28 * Resolves external properties from an
29 * underlying {@code Properties} object.
30 *
31 */
32 public final class PropertiesExpander
33 implements PropertyResolver {
34
35 /** The underlying values. */
36 private final Map<String, String> values;
37
38 /**
39 * Creates a new PropertiesExpander.
40 *
41 * @param properties the underlying properties to use for
42 * property resolution.
43 * @throws IllegalArgumentException when properties argument is null
44 */
45 public PropertiesExpander(Properties properties) {
46 if (properties == null) {
47 throw new IllegalArgumentException("cannot pass null");
48 }
49 values = properties.stringPropertyNames()
50 .stream()
51 .collect(
52 Collectors.toUnmodifiableMap(Function.identity(), properties::getProperty));
53 }
54
55 @Override
56 public String resolve(String name) {
57 return values.get(name);
58 }
59
60 }