001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019
020package org.apache.commons.jcs3.jcache.lang;
021
022public interface Subsitutor
023{
024    String substitute(String value);
025
026    class Helper {
027        public static final Subsitutor INSTANCE;
028        static {
029            Subsitutor value = null;
030            for (final String name : new String[]
031            { // ordered by features
032                    "org.apache.commons.jcs3.jcache.lang.Lang3Substitutor",
033                    "org.apache.commons.jcs3.jcache.lang.DefaultSubsitutor"
034            })
035            {
036                try
037                {
038                    value = (Subsitutor) Subsitutor.class.getClassLoader().loadClass(name).getDeclaredConstructor().newInstance();
039                    value.substitute("${java.version}"); // ensure it works
040                }
041                catch (final Throwable e) // not Exception otherwise NoClassDefFoundError
042                {
043                    // no-op: next
044                }
045            }
046            if (value == null) {
047                throw new IllegalStateException("Can't find a " + Subsitutor.class.getName());
048            }
049            INSTANCE = value;
050        }
051    }
052}