1 /*
2 * Copyright 2005-2007 The Kuali Foundation
3 *
4 *
5 * Licensed under the Educational Community License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.opensource.org/licenses/ecl2.php
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.kuali.rice.core.resourceloader;
18
19 import java.util.ArrayList;
20 import java.util.List;
21
22 /**
23 * Utility class that binds/unbinds the context ClassLoader of the current Thread
24 * using a ThreadLocal.
25 * This class supports re-entrancy by maintaining a stack of context classloaders.
26 * NOTE: maybe implement stricter checks, by matching some contextual object or original
27 * classloader on bind to the unbind so that they are always matched (within a given context)
28 *
29 * @author Kuali Rice Team (rice.collab@kuali.org)
30 */
31 public final class ContextClassLoaderBinder {
32
33 /**
34 * Stack of previous context classloaders that should be
35 * restored on unbind
36 */
37 private static final ThreadLocal<List<ClassLoader>> STACK = new ThreadLocal<List<ClassLoader>>() {
38 protected List<ClassLoader> initialValue() {
39 return new ArrayList<ClassLoader>(5);
40 }
41 };
42
43 private static List<ClassLoader> getStack() {
44 return STACK.get();
45 }
46
47 public static void bind(ClassLoader cl) {
48 List<ClassLoader> stack = getStack();
49 Thread current = Thread.currentThread();
50 //log.debug("[bind] Switching CCL from " + current.getContextClassLoader() + " to " + cl);
51 // push the current context classloader on the stack
52 stack.add(current.getContextClassLoader());
53 current.setContextClassLoader(cl);
54 }
55
56 public static void unbind() {
57 List<ClassLoader> stack = getStack();
58 if (stack.size() == 0) {
59 throw new IllegalStateException("No context classloader to unbind!");
60 }
61 // pop the last context classloader off the stack
62 ClassLoader lastClassLoader = stack.get(stack.size() - 1);
63 //log.debug("[unbind] Switching CCL from " + Thread.currentThread().getContextClassLoader() + " to " + lastClassLoader);
64 stack.remove(stack.size() - 1);
65 Thread.currentThread().setContextClassLoader(lastClassLoader);
66 }
67 }