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Java > Open Source Codes > org > apache > servicemix > beanflow > DefaultState


1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements. See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License. You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
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.apache.servicemix.beanflow;
18
19 import org.apache.servicemix.beanflow.support.Notifier;
20 import org.apache.servicemix.beanflow.support.SynchronousNotifier;
21
22 /**
23  * A default implementation where the state changes are thread safe and the
24  * notifications are made outside of the synchronized block to be reentrant.
25  *
26  * @version $Revision: $
27  */
28 public class DefaultState<T> implements State<T> {
29
30     private T value;
31     private Object JavaDoc lock = new Object JavaDoc();
32     private Notifier notifier;
33
34     public DefaultState() {
35         notifier = new SynchronousNotifier();
36     }
37
38     public DefaultState(T value) {
39         this();
40         this.value = value;
41     }
42
43     public DefaultState(Notifier notifier) {
44         this.notifier = notifier;
45     }
46
47     public DefaultState(T value, Notifier notifier) {
48         this.value = value;
49         this.notifier = notifier;
50     }
51
52     public T get() {
53         synchronized (lock) {
54             return value;
55         }
56     }
57
58     public T getAndSet(T value) {
59         T answer = null;
60         synchronized (lock) {
61             answer = this.value;
62             this.value = value;
63         }
64
65         notifier.run();
66         return answer;
67     }
68
69     public void set(T value) {
70         synchronized (lock) {
71             this.value = value;
72         }
73
74         notifier.run();
75     }
76
77     public boolean compareAndSet(T expected, T newValue) {
78         synchronized (lock) {
79             if (equals(value, expected)) {
80                 this.value = newValue;
81                 return true;
82             }
83         }
84         return false;
85     }
86
87     public void addRunnable(Runnable JavaDoc listener) {
88         notifier.addRunnable(listener);
89     }
90
91     public void removeRunnable(Runnable JavaDoc listener) {
92         notifier.removeRunnable(listener);
93     }
94
95     public String JavaDoc toString() {
96         T currentValue = get();
97         if (currentValue == null) {
98             return "null";
99         }
100         else {
101             return currentValue.toString();
102         }
103     }
104
105     /**
106      * Returns true if the current value is equal to the given value
107      */
108     public boolean is(T that) {
109         T currentValue = get();
110         return equals(that, currentValue);
111     }
112
113     public boolean isAny(T... values) {
114         T currentValue = get();
115         for (T value : values) {
116             if (equals(currentValue, value)) {
117                 return true;
118             }
119         }
120         return false;
121     }
122
123     /**
124      * Returns true if the two values are equal, handling null pointers
125      * gracefully
126      */
127     public static boolean equals(Object JavaDoc value1, Object JavaDoc value2) {
128         if (value1 == value2) {
129             return true;
130         }
131         if (value1 == null || value2 == null) {
132             return false;
133         }
134         return value1.equals(value2);
135     }
136 }
137
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