EnvironmentLookup.java

  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.  * <p>
  20.  * A specialized lookup implementation that allows access to environment variables.
  21.  * </p>
  22.  * <p>
  23.  * This implementation relies on {@link System#getenv()} to resolve environment variables. It can be used for
  24.  * referencing environment variables in configuration files in an easy way, for instance:
  25.  * </p>
  26.  *
  27.  * <pre>
  28.  * java.home = ${env:JAVA_HOME}
  29.  * </pre>
  30.  *
  31.  * <p>
  32.  * {@code EnvironmentLookup} is one of the standard lookups that is registered per default for each configuration.
  33.  * </p>
  34.  *
  35.  * @since 1.7
  36.  * @deprecated Use {@link DefaultLookups#ENVIRONMENT}.
  37.  */
  38. @Deprecated
  39. public class EnvironmentLookup implements Lookup {
  40.     /**
  41.      * Performs a lookup for the specified variable. This implementation directly delegates to a {@code System.getenv()}.
  42.      *
  43.      * @param key the key to lookup
  44.      * @return the value of this key or <strong>null</strong> if it cannot be resolved
  45.      */
  46.     @Override
  47.     public String lookup(final String key) {
  48.         return System.getenv(key);
  49.     }
  50. }