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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  import java.util.Properties;
20  
21  /**
22   * {@link org.codehaus.plexus.interpolation.fixed.FixedValueSource} implementation that wraps a {@link java.util.Properties} instance,
23   * and does a simple lookup of the entire expression string as the parameter for
24   * {@link java.util.Properties#getProperty(String)}, returning the result as the resolved
25   * value.
26   *
27   * @author jdcasey
28   */
29  public class PropertiesBasedValueSource implements FixedValueSource {
30  
31      private final Properties properties;
32  
33      /**
34       * Wrap the specified {@link java.util.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          this.properties = properties;
41      }
42  
43      /**
44       * @return the result of {@link java.util.Properties#getProperty(String)}, using the
45       * entire expression as the key to lookup. If the wrapped properties instance
46       * is null, simply return null.
47       */
48      public Object getValue(String expression, InterpolationState interpolationState) {
49          return properties == null ? null : properties.getProperty(expression);
50      }
51  }