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// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
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 static org.apache.juneau.common.internal.StringUtils.*;
016
017import org.apache.juneau.collections.*;
018import org.apache.juneau.svl.*;
019
020/**
021 * JVM args variable resolver.
022 *
023 * <p>
024 * The format for this var is <js>"$A{arg[,default]}"</js>.
025 *
026 * <p>
027 * This variable resolver requires that the command-line arguments be made available through any of the following:
028 * <ul class='spaced-list'>
029 *    <li><js>"sun.java.command"</js> system property.
030 *    <li><js>"juneau.args"</js> system property.
031 *    <li>{@link #init(Args)} has been called.
032 * </ul>
033 *
034 * <h5 class='section'>Example:</h5>
035 * <p class='bjava'>
036 *    <jc>// Create an args object from the main(String[]) method.</jc>
037 *    Args <jv>args</jv> = <jk>new</jk> Args(<jv>argv</jv>);
038 *
039 *    ArgsVar.<jsm>init</jsm>(<jv>args</jv>);
040 *
041 *    <jc>// Create a variable resolver that resolves JVM arguments (e.g. "$A{1}")</jc>
042 *    VarResolver <jv>varResolver</jv> = VarResolver.<jsm>create</jsm>().vars(ArgsVar.<jk>class</jk>).build();
043 *
044 *    <jc>// Use it!</jc>
045 *    System.<jsf>out</jsf>.println(<jv>varResolver</jv>.resolve(<js>"Arg #1 is set to $A{1}"</js>));
046 * </p>
047 *
048 * <p>
049 * Since this is a {@link SimpleVar}, any variables contained in the result will be recursively resolved.
050 * Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
051 *
052 * <h5 class='section'>See Also:</h5><ul>
053 *    <li class='link'><a class="doclink" href="../../../../../index.html#jm.SimpleVariableLanguage">Simple Variable Language</a>
054 * </ul>
055 */
056public class ArgsVar extends DefaultingVar {
057
058   /** The name of this variable. */
059   public static final String NAME = "A";
060
061   private static volatile Args ARGS;
062
063   /**
064    * Initialize the args for this variable.
065    *
066    * @param args The parsed command-line arguments.
067    */
068   public static void init(Args args) {
069      ARGS = args;
070   }
071
072   private final Args args;
073
074   /**
075    * Constructor.
076    */
077   public ArgsVar() {
078      super(NAME);
079      if (ARGS != null)
080         this.args = ARGS;
081      else {
082         String s = System.getProperty("sun.java.command");
083         if (isNotEmpty(s)) {
084            int i = s.indexOf(' ');
085            args = new Args(i == -1 ? "" : s.substring(i+1));
086         } else {
087            args = new Args(System.getProperty("juneau.args", ""));
088         }
089      }
090   }
091
092   @Override /* Var */
093   public String resolve(VarResolverSession session, String key) {
094      return args.getArg(key);
095   }
096}