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.juneau.svl.vars;
018
019import org.apache.juneau.svl.*;
020
021/**
022 * System property variable resolver.
023 *
024 * <p>
025 * The format for this var is <js>"$S{systemProperty[,defaultValue]}"</js></js>
026 *
027 * <h5 class='section'>Example:</h5>
028 * <p class='bjava'>
029 *    <jc>// Create a variable resolver that resolves system properties (e.g. "$S{java.home}")</jc>
030 *    VarResolver <jv>varResolver</jv> = VarResolver.<jsm>create</jsm>().vars(SystemPropertiesVar.<jk>class</jk>).build();
031 *
032 *    <jc>// Use it!</jc>
033 *    System.<jsf>out</jsf>.println(<jv>varResolver</jv>.resolve(<js>"java.home is set to $S{java.home}"</js>));
034 * </p>
035 *
036 * <p>
037 * Since this is a {@link SimpleVar}, any variables contained in the result will be recursively resolved.
038 * <br>Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
039 *
040 * <h5 class='section'>See Also:</h5><ul>
041 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/SimpleVariableLanguageBasics">Simple Variable Language Basics</a>
042 * </ul>
043 */
044public class SystemPropertiesVar extends MapVar {
045
046   /** The name of this variable. */
047   public static final String NAME = "S";
048
049   /**
050    * Constructor.
051    */
052   public SystemPropertiesVar() {
053      super(NAME, System.getProperties());
054   }
055}