ResolverFactory


1   package de.webman.acl.resolver;
2   
3   import java.util.Enumeration  ;
4   import java.util.Hashtable  ;
5   import com.teamkonzept.lib.ConfigurationManager;
6   import com.teamkonzept.lib.TKException;
7   import de.webman.acl.Login;
8   
9   /**
10   * Simple factory for resolver objects. The resolver object is created
11   * and cached the first time it is requested. Thus, subsequent requests
12   * are served by the cache.
13   * <P>
14   * The factory is free to choose the <CODE>Resolver</CODE> implementation.
15   * At this time, only <CODE>SequentialResolver</CODE> is used.
16   *
17   * @version 1.0
18   * @since 1.0
19   * @author &copy; 2001 Webman AG
20   */
21  public class ResolverFactory
22  {
23  
24      // $Header: /cvsroot/webman-cms/source/webman/de/webman/acl/resolver/ResolverFactory.java,v 1.1 2001/08/20 08:25:09 mischa Exp $
25  
26      // Constants
27  
28      /**
29       * Singleton instance.
30       */
31      private static ResolverFactory SINGLETON = null;
32  
33  
34      // Attributes
35  
36      /**
37       * Internal sequential resolver cache.
38       */
39      private Hashtable   sequentials = null;
40  
41      /**
42       * Internal sequential resolver cache.
43       */
44      private Hashtable   generics = null;
45  
46  
47      // Constructors
48  
49      /**
50       * Inhibits instantiation from outside.
51       */
52      private ResolverFactory ()
53      {
54          // Create different caches for both kinds of resolvers.
55          this.sequentials = new Hashtable  ();
56          this.generics = new Hashtable  ();
57      }
58  
59  
60      // Instance
61  
62      /**
63       * Returns the singleton instance of the factory.
64       *
65       * @return the singleton instance of the factory.
66       */
67      public static synchronized final ResolverFactory getInstance ()
68      {
69          if (SINGLETON == null)
70          {
71              SINGLETON = new ResolverFactory();
72          }
73  
74          return SINGLETON;
75      }
76  
77  
78      // Resolver and Checker access
79  
80      /**
81       * Returns a resolver for the given login object.
82       *
83       * @param login the login object.
84       * @return a resolver for the given login object.
85       * @exception com.teamkonzept.lib.TKException if an error occured during resolver creation.
86       */
87      public final Resolver getResolver (Login login)
88          throws TKException
89      {
90          // Cache lookup.
91          Resolver resolver = (Resolver) sequentials.get(login.getID());
92  
93          if (resolver == null)
94          {
95              // Create sequential resolver.
96              resolver = new SequentialResolver(login);
97  
98              // Configure sequential resolver.
99              resolver.configurationChanged();
100 
101             // Register sequential resolver.
102             register(resolver);
103 
104             // Cache sequential resolver.
105             sequentials.put(login.getID(), resolver);
106         }
107 
108         return resolver;
109     }
110 
111 // Cascading resolver access
112 
113     /**
114      * Returns an additional resolver for the requesting resolver.
115      *
116      * @param requester the requesting resolver.
117      * @return an additional resolver for the requesting resolver.
118      * @exception com.teamkonzept.lib.TKException if an error occured during resolver creation.
119      */
120     protected final Resolver getResolver (Resolver requester)
121         throws TKException
122     {
123         // Cache lookup.
124         Resolver resolver = (Resolver) generics.get(requester.getLogin().getID());
125 
126         if (resolver == null)
127         {
128             // Create generic resolver.
129             resolver = new GenericResolver(requester.getLogin());
130 
131             // Configure generic resolver.
132             resolver.configurationChanged();
133 
134             // Register generic resolver.
135             register(resolver);
136 
137             // Cache generic resolver.
138             generics.put(requester.getLogin().getID(), resolver);
139         }
140 
141         return resolver;
142     }
143 
144 
145     /**
146      * Returns a checker for the given login object.
147      *
148      * @param login the login object.
149      * @return a checker for the given login object.
150      * @exception com.teamkonzept.lib.TKException if an error occured during resolver creation.
151      */
152     public final Checker getChecker (Login login)
153         throws TKException
154     {
155         return (Checker) getResolver(login);
156     }
157 
158     /**
159      * Removes the resolver for the given login object from the cache.
160      *
161      * @param login the login object.
162      */
163     public final void removeResolver (Login login)
164     {
165         // Remove sequential resolver from cache and deregister it.
166         deregister((Resolver) sequentials.remove(login.getID()));
167 
168         // Remove generic resolver from cache and deregister it.
169         deregister((Resolver) generics.remove(login.getID()));
170     }
171 
172     /**
173      * Removes all resolvers from the cache.
174      */
175     public final void removeResolvers ()
176     {
177         // Get all sequential resolvers.
178         Enumeration   iterator = sequentials.elements();
179 
180         // Deregister all sequential resolvers.
181         while (iterator.hasMoreElements())
182         {
183             deregister((Resolver) iterator.nextElement());
184         }
185 
186         // Clear sequential resolver cache.
187         sequentials.clear();
188 
189         // Get all generic resolvers.
190         iterator = generics.elements();
191 
192         // Deregister all generic resolvers.
193         while (iterator.hasMoreElements())
194         {
195             deregister((Resolver) iterator.nextElement());
196         }
197 
198         // Clear generic resolver cache.
199         generics.clear();
200     }
201     
202 
203     // Convenvience methods
204 
205     /**
206      * Registers the given resolver with the configuration manager.
207      *
208      * @param resolver the resolver.
209      */
210     private void register (Resolver resolver)
211     {
212         ConfigurationManager.getInstance()
213                             .registerConfigurationListener(resolver,
214                                                            Resolver.PROPERTY_GROUP_NAME);
215     }
216 
217     /**
218      * Deregisters the given resolver with the configuration manager.
219      *
220      * @param resolver the resolver.
221      */
222     private void deregister (Resolver resolver)
223     {
224         ConfigurationManager.getInstance()
225                             .deregisterConfigurationListener(resolver,
226                                                              Resolver.PROPERTY_GROUP_NAME);
227     }
228 
229 }
230
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