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.commons.svl;
018
019import static org.apache.juneau.commons.utils.Shorts.*;
020import static org.apache.juneau.commons.utils.StringUtils.*;
021
022/**
023 * Interface for the resolution of vars that can have one or more keys where the first non-null resolution is returned.
024 *
025 * <p>
026 * For example, to resolve the system property <js>"myProperty"</js> but then resolve <js>"myProperty2"</js> if the
027 * property doesn't exist: <js>"$S{myProperty1,myProperty2}"</js>
028 *
029 * <p>
030 * Subclasses must implement the following method:
031 * <ul class='javatree'>
032 *    <li class='jm'>{@link #resolve(VarResolverSession, String)}
033 * </ul>
034 *
035 * <h5 class='section'>See Also:</h5><ul>
036 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/MarshallSimpleVariableLanguage">Marshall Simple Variable Language</a>
037 * </ul>
038 */
039public abstract class MultipartResolvingVar extends SimpleVar {
040
041   /**
042    * Constructor.
043    *
044    * @param name The name of this variable.  Must not be <jk>null</jk>.
045    */
046   protected MultipartResolvingVar(String name) {
047      super(name);
048   }
049
050   @Override /* Overridden from Var */
051   public String doResolve(VarResolverSession session, String s) throws Exception {
052      var i = s.indexOf(',');
053      if (i == -1)
054         return resolve(session, s.trim());
055      for (var s2 : splita(s)) {
056         var v = resolve(session, s2);
057         if (nn(v))
058            return v;
059      }
060      return null;
061   }
062}