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Java > Open Source Codes > org > directwebremoting > guice > AbstractMapContextScope


1 /*
2  * Copyright 2007 Tim Peierls
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 org.directwebremoting.guice;
17
18 import com.google.inject.Key;
19
20 import java.util.Collection JavaDoc;
21 import java.util.concurrent.ConcurrentHashMap JavaDoc;
22 import java.util.concurrent.ConcurrentMap JavaDoc;
23
24 /**
25  * A specialization of {@link AbstractContextScope} using a concurrent map
26  * to hold registered instance providers. Concrete implementations must
27  * define {@code get()} to return the current context, and they must call
28  * {@code super(C.class)} in constructors.
29  * @author Tim Peierls [tim at peierls dot net]
30  */
31 public abstract class AbstractMapContextScope<C>
32     extends AbstractContextScope<C, ConcurrentMap JavaDoc>
33 {
34     protected AbstractMapContextScope(Class JavaDoc<C> type, String JavaDoc scopeName)
35     {
36         super(type, scopeName);
37     }
38     
39     public abstract C get();
40     
41     
42     //
43 // ContextRegistry methods
44 //
45
46     public ConcurrentMap JavaDoc registryFor(C context)
47     {
48         ConcurrentMap JavaDoc instanceMap = map.get(context);
49
50         if (instanceMap == null)
51         {
52             ConcurrentMap JavaDoc emptyMap = new ConcurrentHashMap JavaDoc();
53             instanceMap = map.putIfAbsent(context, emptyMap);
54             if (instanceMap == null)
55             {
56                 instanceMap = emptyMap;
57             }
58         }
59
60         return instanceMap;
61     }
62
63     public <T> InstanceProvider<T> get(ConcurrentMap JavaDoc registry, Key<T> key, String JavaDoc keyString)
64     {
65         @SuppressWarnings JavaDoc("unchecked")
66         ConcurrentMap JavaDoc<Key<T>, InstanceProvider<T>> instanceMap =
67             (ConcurrentMap JavaDoc<Key<T>, InstanceProvider<T>>) registry;
68         return instanceMap.get(key);
69     }
70     
71     public <T> InstanceProvider<T> putIfAbsent(ConcurrentMap JavaDoc registry,
72                                                Key<T> key, String JavaDoc keyString,
73                                                InstanceProvider<T> creator)
74     {
75         @SuppressWarnings JavaDoc("unchecked")
76         ConcurrentMap JavaDoc<Key<T>, InstanceProvider<T>> instanceMap =
77             (ConcurrentMap JavaDoc<Key<T>, InstanceProvider<T>>) registry;
78         
79         return instanceMap.putIfAbsent(key, creator);
80     }
81     
82     public <T> boolean remove(ConcurrentMap JavaDoc registry, Key<T> key, String JavaDoc keyString,
83                               InstanceProvider<T> creator)
84     {
85         @SuppressWarnings JavaDoc("unchecked")
86         ConcurrentMap JavaDoc<Key<T>, InstanceProvider<T>> instanceMap =
87             (ConcurrentMap JavaDoc<Key<T>, InstanceProvider<T>>) registry;
88         
89         return instanceMap.remove(key, creator);
90     }
91
92     private final ConcurrentMap JavaDoc<C, ConcurrentMap JavaDoc> map =
93           new ConcurrentHashMap JavaDoc<C, ConcurrentMap JavaDoc>();
94 }
95
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