1 /*
2 * Copyright 2007-2013 smartics, Kronseder & Reiner GmbH
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package de.smartics.exceptions.runtime;
17
18 import de.smartics.util.lang.Arg;
19
20 /**
21 * Allows to provide a fallback, secondary class loader to be consulted, if the
22 * primary class loader cannot provide a resource.
23 */
24 public final class FallbackClassLoader extends ClassLoader
25 {
26 // ********************************* Fields *********************************
27
28 // --- constants ------------------------------------------------------------
29
30 // --- members --------------------------------------------------------------
31
32 /**
33 * The class loader consulted first.
34 */
35 private final ClassLoader primaryClassLoader;
36
37 // ****************************** Initializer *******************************
38
39 // ****************************** Constructors ******************************
40
41 /**
42 * Default constructor.
43 *
44 * @param primaryClassLoader the class loader consulted first.
45 * @param secondaryClassLoader the class loader consulted, if resource cannot
46 * be found by primary class loader.
47 */
48 public FallbackClassLoader(final ClassLoader primaryClassLoader,
49 final ClassLoader secondaryClassLoader)
50 {
51 super(secondaryClassLoader);
52 this.primaryClassLoader =
53 Arg.checkNotNull("primaryClassLoader", primaryClassLoader);
54 }
55
56 // ****************************** Inner Classes *****************************
57
58 // ********************************* Methods ********************************
59
60 // --- init -----------------------------------------------------------------
61
62 // --- get&set --------------------------------------------------------------
63
64 // --- business -------------------------------------------------------------
65
66 @Override
67 protected Class<?> findClass(final String name) throws ClassNotFoundException
68 {
69 if (primaryClassLoader != null)
70 {
71 return primaryClassLoader.loadClass(name);
72 }
73 else
74 {
75 return super.findClass(name);
76 }
77 }
78
79 // --- object basics --------------------------------------------------------
80
81 }