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1   package org.codehaus.plexus.interpolation.fixed;
2   
3   /*
4    * Copyright 2014 The 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  
20  import java.util.Properties;
21  
22  /**
23   * {@link org.codehaus.plexus.interpolation.fixed.FixedValueSource} implementation that wraps a {@link java.util.Properties} instance,
24   * and does a simple lookup of the entire expression string as the parameter for
25   * {@link java.util.Properties#getProperty(String)}, returning the result as the resolved
26   * value.
27   *
28   * @author jdcasey
29   * @version $Id$
30   */
31  public class PropertiesBasedValueSource
32      implements FixedValueSource
33  {
34  
35      private final Properties properties;
36  
37      /**
38       * Wrap the specified {@link java.util.Properties} object for use as a value source.
39       * Nulls are allowed.
40       *
41       * @param properties The properties instance to wrap.
42       */
43      public PropertiesBasedValueSource( Properties properties )
44      {
45          this.properties = properties;
46      }
47  
48      /**
49       * @return the result of {@link java.util.Properties#getProperty(String)}, using the
50       * entire expression as the key to lookup. If the wrapped properties instance
51       * is null, simply return null.
52       */
53  
54      public Object getValue( String expression, InterpolationState interpolationState )
55      {
56          return properties == null ? null : properties.getProperty( expression );
57      }
58  
59  }