UIContextService


1   /*
2    * Copyright (C) 2005 Alfresco, Inc.
3    *
4    * Licensed under the Mozilla Public License version 1.1 
5    * with a permitted attribution clause. You may obtain a
6    * copy of the License at
7    *
8    *   http://www.alfresco.org/legal/license.txt
9    *
10   * Unless required by applicable law or agreed to in writing,
11   * software distributed under the License is distributed on an
12   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
13   * either express or implied. See the License for the specific
14   * language governing permissions and limitations under the
15   * License.
16   */
17  package org.alfresco.web.app.context;
18  
19  import java.util.HashMap  ;
20  import java.util.Map  ;
21  
22  import javax.faces.context.FacesContext;
23  
24  /**
25   * Beans supporting the IContextListener interface are registered against this class. Then Beans
26   * which wish to indicate that the UI should refresh itself i.e. dump all cached data and settings,
27   * call the UIContextService.notifyBeans() to inform all registered instances of the change. 
28   * 
29   * @author Kevin Roast
30   */
31  public final class UIContextService
32  {
33     /**
34      * Private constructor
35      */
36     private UIContextService()
37     {
38     }
39     
40     /**
41      * Returns a Session local instance of the UIContextService
42      * 
43      * @return UIContextService for this Thread
44      */
45     public static UIContextService getInstance(FacesContext fc)
46     {
47        Map   session = fc.getExternalContext().getSessionMap();
48        UIContextService service = (UIContextService)session.get(CONTEXT_KEY);
49        if (service == null)
50        {
51           service = new UIContextService();
52           session.put(CONTEXT_KEY, service);
53        }
54        
55        return service;
56     }
57     
58     /**
59      * Register a bean to be informed of context events
60      * 
61      * @param bean    Conforming to the IContextListener interface
62      */
63     public void registerBean(IContextListener bean)
64     {
65        if (bean == null)
66        {
67           throw new IllegalArgumentException  ("Bean reference specified cannot be null!");
68        }
69        
70        this.registeredBeans.put(bean.getClass(), bean);
71     }
72     
73     /**
74      * Remove a bean reference from those notified of changes
75      * 
76      * @param bean    Conforming to the IContextListener interface
77      */
78     public void unregisterBean(IContextListener bean)
79     {
80        if (bean == null)
81        {
82           throw new IllegalArgumentException  ("Bean reference specified cannot be null!");
83        }
84        
85        this.registeredBeans.remove(bean);
86     }
87     
88     /**
89      * Call to notify all register beans that the UI context has changed and they should
90      * refresh themselves as appropriate.
91      */
92     public void notifyBeans()
93     {
94        for (IContextListener listener: this.registeredBeans.values())
95        {
96           listener.contextUpdated();
97        }
98     }
99     
100    
101    /** key for the UI context service in the session */
102    private final static String   CONTEXT_KEY = "__uiContextService";
103    
104    /** Map of bean registered against the context service */
105    private Map  <Class  , IContextListener> registeredBeans = new HashMap  <Class  , IContextListener>(7, 1.0f);
106 }
107
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