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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.commons.configuration2.interpol;
18  
19  import org.apache.commons.text.lookup.StringLookupFactory;
20  
21  /**
22   * <p>
23   * A specialized implementation of the {@code Lookup} interface that allows access to system properties.
24   * </p>
25   * <p>
26   * This implementation relies on {@code StrLookup.systemPropertiesLookup()} from the Commons Lang project to resolve
27   * system properties. It can be used for referencing system properties in configuration files in an easy way, for
28   * instance:
29   * </p>
30   *
31   * <pre>
32   * current.user = ${sys:user.name}
33   * </pre>
34   *
35   * <p>
36   * {@code SystemPropertiesLookup} is one of the standard lookups that is registered per default for each configuration.
37   * </p>
38   *
39   * @since 2.0
40   * @deprecated Use {@link DefaultLookups#SYSTEM_PROPERTIES}.
41   */
42  @Deprecated
43  public class SystemPropertiesLookup implements Lookup {
44      @Override
45      public Object lookup(final String variable) {
46          return StringLookupFactory.INSTANCE.systemPropertyStringLookup().lookup(variable);
47      }
48  }