1 /**
2 * Copyright 2005-2011 The Kuali Foundation
3 *
4 * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
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 org.kuali.rice.core.api.util;
17
18 import java.util.ArrayList;
19 import java.util.List;
20
21 /**
22 * Utility class that binds/unbinds the context ClassLoader of the current Thread
23 * using a ThreadLocal.
24 * This class supports re-entrancy by maintaining a stack of context classloaders.
25 * NOTE: maybe implement stricter checks, by matching some contextual object or original
26 * classloader on bind to the unbind so that they are always matched (within a given context)
27 *
28 * @author Kuali Rice Team (rice.collab@kuali.org)
29 */
30 public final class ContextClassLoaderBinder {
31
32 /**
33 * Stack of previous context classloaders that should be
34 * restored on unbind
35 */
36 private static final ThreadLocal<List<ClassLoader>> STACK = new ThreadLocal<List<ClassLoader>>() {
37 protected List<ClassLoader> initialValue() {
38 return new ArrayList<ClassLoader>(5);
39 }
40 };
41
42 private static List<ClassLoader> getStack() {
43 return STACK.get();
44 }
45
46 public static void bind(ClassLoader cl) {
47 List<ClassLoader> stack = getStack();
48 Thread current = Thread.currentThread();
49 //log.debug("[bind] Switching CCL from " + current.getContextClassLoader() + " to " + cl);
50 // push the current context classloader on the stack
51 stack.add(current.getContextClassLoader());
52 current.setContextClassLoader(cl);
53 }
54
55 public static void unbind() {
56 List<ClassLoader> stack = getStack();
57 if (stack.size() == 0) {
58 throw new IllegalStateException("No context classloader to unbind!");
59 }
60 // pop the last context classloader off the stack
61 ClassLoader lastClassLoader = stack.get(stack.size() - 1);
62 //log.debug("[unbind] Switching CCL from " + Thread.currentThread().getContextClassLoader() + " to " + lastClassLoader);
63 stack.remove(stack.size() - 1);
64 Thread.currentThread().setContextClassLoader(lastClassLoader);
65 }
66 }