1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19
20 package org.apache.commons.jcs.jcache.lang;
21
22 public interface Subsitutor
23 {
24 String substitute(String value);
25
26 public static class Helper {
27 public static final Subsitutor INSTANCE;
28 static {
29 Subsitutor value = null;
30 for (final String name : new String[]
31 { // ordered by features
32 "org.apache.commons.jcs.jcache.lang.Lang3Substitutor",
33 "org.apache.commons.jcs.jcache.lang.DefaultSubsitutor"
34 })
35 {
36 try
37 {
38 value = Subsitutor.class.cast(
39 Subsitutor.class.getClassLoader().loadClass(name).newInstance());
40 value.substitute("${java.version}"); // ensure it works
41 }
42 catch (final Throwable e) // not Exception otherwise NoClassDefFoundError
43 {
44 // no-op: next
45 }
46 }
47 if (value == null) {
48 throw new IllegalStateException("Can't find a " + Subsitutor.class.getName());
49 }
50 INSTANCE = value;
51 }
52 }
53 }