1 package org.codehaus.plexus.interpolation;
2
3 /*
4 * Copyright 2001-2008 Codehaus Foundation.
5 *
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18
19 import java.util.Properties;
20
21 /**
22 * {@link ValueSource} implementation that wraps a {@link Properties} instance,
23 * and does a simple lookup of the entire expression string as the parameter for
24 * {@link Properties#getProperty(String)}, returning the result as the resolved
25 * value.
26 *
27 * @author jdcasey
28 */
29 public class PropertiesBasedValueSource extends AbstractValueSource {
30
31 private final Properties properties;
32
33 /**
34 * Wrap the specified {@link Properties} object for use as a value source.
35 * Nulls are allowed.
36 *
37 * @param properties The properties instance to wrap.
38 */
39 public PropertiesBasedValueSource(Properties properties) {
40 super(false);
41 this.properties = properties;
42 }
43
44 /**
45 * @return the result of {@link Properties#getProperty(String)}, using the
46 * entire expression as the key to lookup. If the wrapped properties instance
47 * is null, simply return null.
48 */
49 public Object getValue(String expression) {
50 return properties == null ? null : properties.getProperty(expression);
51 }
52 }