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1   /*
2    * Copyright 2002,2004 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  package org.apache.commons.jelly.impl;
17  
18  import java.util.HashMap;
19  import java.util.Map;
20  
21  import org.apache.commons.jelly.JellyException;
22  import org.apache.commons.jelly.Script;
23  import org.apache.commons.jelly.Tag;
24  import org.apache.commons.jelly.TagLibrary;
25  import org.xml.sax.Attributes;
26  
27  /***
28   * <p><code>DynamicTagLibrary</code> represents a TagLibrary which
29   * gets created by running a Jelly script.</p>
30   *
31   * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
32   * @version $Revision: 155420 $
33   */
34  public class DynamicTagLibrary extends TagLibrary {
35  
36      private String uri;
37      private Map templates = new HashMap();
38      private TagLibrary parent;
39  
40      public DynamicTagLibrary() {
41      }
42  
43      public DynamicTagLibrary(String uri) {
44          this.uri = uri;
45      }
46  
47      /*** Creates a new script to execute the given tag name and attributes */
48      public TagScript createTagScript(final String name, final Attributes attributes)
49          throws JellyException {
50  
51          return new TagScript(
52              new TagFactory() {
53                  public Tag createTag(String name, Attributes attributes) throws JellyException {
54                      return DynamicTagLibrary.this.createTag(name, attributes);
55                  }
56              }
57          );
58      }
59  
60      /*** Creates a new Tag for the given tag name if it exists */
61      public Tag createTag(String name, Attributes attributes)
62          throws JellyException {
63  
64          Object value = templates.get(name);
65          if ( value instanceof Script ) {
66              Script template = (Script) value;
67              return new DynamicTag(template);
68          }
69          else if ( value instanceof TagFactory ) {
70              TagFactory factory = (TagFactory) value;
71              return factory.createTag(name, attributes);
72          }
73          else if ( parent != null ) {
74              // delegate to the parent
75              return parent.createTag(name, attributes);
76          }
77  
78          return null;
79      }
80  
81      /***
82       * Creates a new tag with the given name and template
83       */
84      public void registerDynamicTag(String name, Script template) {
85          templates.put(name, template);
86      }
87  
88      /***
89       * Creates a new Jelly Bean Tag with the given name
90       */
91      public void registerBeanTag(String name, TagFactory factory) {
92          templates.put(name, factory);
93      }
94  
95      /***
96       * Returns the script associated with the given tag name
97       *
98       * @param name The tag name
99       * @return The script associated with <code>name</code>, or
100      *         <code>null</code> if the tag doesn't exist or isn't a script
101      */
102     public Script getDynamicTag(String name) {
103         Object result = templates.get(name);
104         return (result instanceof Script) ? (Script) result : null;
105     }
106 
107     /***
108      * Returns the tag library instance which contains the named tag.
109      * <p/>
110      * If the tag is not registered within this library, the set of
111      * parent libraries will be searched.
112      *
113      * @param name The tag name
114      * @return The tag library containing the named tag, or <code>null</code>
115      *         if the tag is not registered.
116      */
117     public DynamicTagLibrary find(String name) {
118         DynamicTagLibrary result = null;
119         if (templates.get(name) != null) {
120             result = this;
121         }
122         else if (parent instanceof DynamicTagLibrary) {
123             result = ((DynamicTagLibrary) parent).find(name);
124         }
125         return result;
126     }
127 
128     // Properties
129     //-------------------------------------------------------------------------
130     public String getUri() {
131         return uri;
132     }
133 
134     public void setUri(String uri) {
135         this.uri = uri;
136     }
137 
138 
139     /***
140      * Returns the parent library which will be used to resolve unknown tags.
141      * @return TagLibrary
142      */
143     public TagLibrary getParent() {
144         return parent;
145     }
146 
147     /***
148      * Sets the parent to inherit tags from that are not defined in this library.
149      * @param parent The parent to set
150      */
151     public void setParent(TagLibrary parent) {
152         this.parent = parent;
153     }
154 
155 }