001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.configuration2.interpol;
018
019import org.apache.commons.text.lookup.StringLookupFactory;
020
021/**
022 * <p>
023 * A specialized implementation of the {@code Lookup} interface that allows access to system properties.
024 * </p>
025 * <p>
026 * This implementation relies on {@code StrLookup.systemPropertiesLookup()} from the Commons Lang project to resolve
027 * system properties. It can be used for referencing system properties in configuration files in an easy way, for
028 * instance:
029 * </p>
030 *
031 * <pre>
032 * current.user = ${sys:user.name}
033 * </pre>
034 *
035 * <p>
036 * {@code SystemPropertiesLookup} is one of the standard lookups that is registered per default for each configuration.
037 * </p>
038 *
039 * @since 2.0
040 * @deprecated Use {@link DefaultLookups#SYSTEM_PROPERTIES}.
041 */
042@Deprecated
043public class SystemPropertiesLookup implements Lookup {
044    @Override
045    public Object lookup(final String variable) {
046        return StringLookupFactory.INSTANCE.systemPropertyStringLookup().lookup(variable);
047    }
048}