001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
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010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.svl.vars;
014
015import org.apache.juneau.svl.*;
016
017/**
018 * System property variable resolver.
019 *
020 * <p>
021 * The format for this var is <js>"$S{systemProperty[,defaultValue]}"</js></js>
022 *
023 * <h5 class='section'>Example:</h5>
024 * <p class='bjava'>
025 *    <jc>// Create a variable resolver that resolves system properties (e.g. "$S{java.home}")</jc>
026 *    VarResolver <jv>varResolver</jv> = VarResolver.<jsm>create</jsm>().vars(SystemPropertiesVar.<jk>class</jk>).build();
027 *
028 *    <jc>// Use it!</jc>
029 *    System.<jsf>out</jsf>.println(<jv>varResolver</jv>.resolve(<js>"java.home is set to $S{java.home}"</js>));
030 * </p>
031 *
032 * <p>
033 * Since this is a {@link SimpleVar}, any variables contained in the result will be recursively resolved.
034 * <br>Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
035 *
036 * <h5 class='section'>See Also:</h5><ul>
037 *    <li class='link'><a class="doclink" href="../../../../../index.html#jm.SimpleVariableLanguage">Simple Variable Language</a>
038 * </ul>
039 */
040public class SystemPropertiesVar extends MapVar {
041
042   /** The name of this variable. */
043   public static final String NAME = "S";
044
045   /**
046    * Constructor.
047    */
048   public SystemPropertiesVar() {
049      super(NAME, System.getProperties());
050   }
051}