01: /*
02: * Copyright 2004-2007 the original author or authors.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
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.springframework.webflow.conversation.impl;
17:
18: import java.io.ObjectStreamException;
19: import java.io.Serializable;
20:
21: /**
22: * A singleton lock that doesn't do anything. For use when conversations don't
23: * require or choose not to implement locking.
24: *
25: * @author Keith Donald
26: */
27: class NoOpConversationLock implements ConversationLock, Serializable {
28:
29: /**
30: * The singleton instance.
31: */
32: public static final NoOpConversationLock INSTANCE = new NoOpConversationLock();
33:
34: /**
35: * Private constructor to avoid instantiation.
36: */
37: private NoOpConversationLock() {
38: }
39:
40: public void lock() {
41: // no-op
42: }
43:
44: public void unlock() {
45: // no-op
46: }
47:
48: // resolve the singleton instance
49: private Object readResolve() throws ObjectStreamException {
50: return INSTANCE;
51: }
52: }
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