NameService


1   /*
2    * Copyright 2005 The Apache Software Foundation.
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   * $Header:$
17   */
18  package org.apache.beehive.netui.pageflow.requeststate;
19  
20  import javax.servlet.http.HttpSession  ;
21  import java.lang.ref.WeakReference  ;
22  import java.util.HashMap  ;
23  
24  /**
25   *
26   */
27  public class NameService
28  {
29      private static final String   NAME_SERVICE = "netui.nameService";
30  
31      private HashMap  /*<String,WeakReference>*/ _nameMap;
32      private int _nextValue;
33  
34      /**
35       * private constructor allowing for a factory method to access NameService objects.
36       */
37      private NameService() {
38          _nameMap = new HashMap  /*<String,WeakReference>*/();
39          _nextValue = 0;
40      }
41  
42      /**
43       * This will return the session specific instance of a NameService.  There
44       * will only be a single NameService per session.
45       * @param session the HttpSession that contains the NameService
46       * @return the NameService associated with the session.
47       */
48      public static NameService instance(HttpSession   session)
49      {
50          // synchronize on the session so we only create a single NameService
51          // within the session.
52          synchronized (session) {
53              NameService nameService = (NameService) session.getAttribute(NAME_SERVICE);
54              if (nameService == null) {
55                  nameService = new NameService();
56                  session.setAttribute(NAME_SERVICE,nameService);
57              }
58              assert(nameService != null) : "Found invalid null name service";
59              return nameService;
60          }
61      }
62  
63      /**
64       * This method will create a unique name for an INameable object.  The name
65       * will be unque within the session.  This will throw an IllegalStateException
66       * if INameable.setObjectName has previously been called on object.
67       * @param namePrefix The prefix of the generated name.
68       * @param object the INameable object.
69       * @throws IllegalStateException if this method is called more than once for an object
70       */
71      public synchronized void nameObject(String   namePrefix, INameable object)
72      {
73          String   name = namePrefix + Integer.toString(_nextValue++);
74          object.setObjectName(name);
75      }
76  
77      /**
78       * This is a debug method that will set the next integer value.  This is used
79       * so tests can force the name.
80       * @param val
81       */
82      public void debugSetNameIntValue(int val) {
83          _nextValue = val;
84      }
85  
86      /**
87       *
88       * @param object
89       */
90      public void put(INameable object) {
91          if (object == null)
92              throw new IllegalStateException  ("object must not be null");
93          String   name = object.getObjectName();
94          if (name == null)
95              throw new IllegalStateException  ("object has not been named");
96  
97          _nameMap.put(name,new WeakReference  (object));
98      }
99  
100     /**
101      *
102      * @param name
103      * @return INameable
104      */
105     public INameable get(String   name) {
106         if (name == null)
107             throw new IllegalStateException  ("name must not be null");
108         WeakReference   wr = (WeakReference  ) _nameMap.get(name);
109         if (wr == null)
110             return null;
111         INameable object = (INameable) wr.get();
112         if (object == null) {
113             _nameMap.remove(name);
114         }
115         return object;
116     }
117 }
118
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