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1   /*
2    * $Id: FactorySet.java 471754 2006-11-06 14:55:09Z husted $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  package org.apache.struts.tiles.xmlDefinition;
23  
24  import java.util.HashMap;
25  import java.util.Iterator;
26  import java.util.Map;
27  
28  import javax.servlet.ServletContext;
29  import javax.servlet.ServletRequest;
30  
31  import org.apache.struts.tiles.ComponentDefinition;
32  import org.apache.struts.tiles.ComponentDefinitionsFactory;
33  import org.apache.struts.tiles.DefinitionsFactoryException;
34  import org.apache.struts.tiles.FactoryNotFoundException;
35  import org.apache.struts.tiles.NoSuchDefinitionException;
36  
37  /**
38   * Component Definitions factory.
39   * This factory contains several factories identified by a key. The
40   * getDefinition() method first looks for the factory key, retrieves or creates this
41   * factory and then calls its getDefinition().
42   */
43  public abstract class FactorySet implements ComponentDefinitionsFactory
44  {
45  
46      /** Loaded factories */
47    protected Map factories=null;
48  
49    /**
50     * Extract key that will be used to get the sub factory.
51     * @param name Name of requested definition.
52     * @param request Current servlet request.
53     * @param servletContext Current servlet context.
54     * @return Object.
55     */
56    abstract protected Object getDefinitionsFactoryKey(String name, ServletRequest request, ServletContext servletContext);
57  
58    /**
59     * Get default factory.
60     * @return Default factory.
61     */
62    abstract protected DefinitionsFactory getDefaultFactory();
63  
64    /**
65     * Get a factory by its key.
66     * If key is <code>null</code>, return defaultFactory.
67     * Search in loaded factories. If not found, create factory and store return value in
68     * loaded factories.
69     * @param key Key of requested definition.
70     * @param request Current servlet request.
71     * @param servletContext Current servlet context.
72     * @throws DefinitionsFactoryException If an error occur while creating factory.
73     */
74    protected DefinitionsFactory getFactory(Object key, ServletRequest request, ServletContext servletContext)
75      throws DefinitionsFactoryException
76    {
77    if(key == null )
78      return getDefaultFactory();
79  
80    Object factory = factories.get( key );
81    if( factory == null )
82      {
83        // synchronize creation to avoid double creation by separate threads.
84        // Also, check if factory hasn't been created while waiting for synchronized
85        // section.
86      synchronized(factories)
87        {
88        factory = factories.get( key );
89        if( factory == null )
90          {
91          factory = createFactory( key, request, servletContext);
92          factories.put( key, factory );
93          } // end if
94        } // end synchronized
95      } // end if
96    return (DefinitionsFactory)factory;
97    }
98  
99    /**
100    * Get a definition by its name.
101    *
102    * @param name Name of requested definition.
103    * @param request Current servlet request.
104    * @param servletContext Current servlet context.
105    * @throws NoSuchDefinitionException No definition found for specified name
106    * @throws DefinitionsFactoryException General exception
107    */
108   public ComponentDefinition getDefinition(String name, ServletRequest request, ServletContext servletContext)
109     throws NoSuchDefinitionException, DefinitionsFactoryException
110   {
111   if( factories == null )
112     throw new FactoryNotFoundException( "No definitions factory defined" );
113 
114   Object key = getDefinitionsFactoryKey( name, request, servletContext);
115   DefinitionsFactory factory = getFactory( key, request, servletContext);
116   return factory.getDefinition( name, request, servletContext );
117   }
118 
119   /**
120    * Create a factory for specified key.
121    * This method is called by getFactory() when the requested factory doesn't already exist.
122    * Must return a factory, or a default one.
123    * Real implementation needs to provide this method.
124    * @param key Key of requested definition.
125    * @param request Current servlet request.
126    * @param servletContext Current servlet context
127    * @throws DefinitionsFactoryException If an error occur while creating factory.
128    */
129   abstract protected DefinitionsFactory createFactory(Object key, ServletRequest request, ServletContext servletContext)
130           throws DefinitionsFactoryException;
131 
132   /**
133    * Init factory set.
134    * @param servletContext Current servlet context
135    * @param properties properties used to initialized factory set;
136    */
137   abstract public void initFactory(ServletContext servletContext, Map properties)
138     throws DefinitionsFactoryException;
139 
140   /**
141    * Constructor.
142    */
143   public FactorySet()
144   {
145   factories = new HashMap();
146   }
147 
148     /**
149      * Return String representation.
150      * @return String representation.
151      */
152   public String toString()
153     {
154     Iterator i = factories.values().iterator();
155     StringBuffer buff = new StringBuffer( "all FactorySet's factory : \n" );
156     while( i.hasNext() )
157       {
158       buff.append( i.next().toString() ).append("\n");
159       }
160     return buff.toString();
161     }
162 
163 }