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Java > Open Source Codes > org > apache > commons > jelly > impl > DynamicTagLibrary


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 JavaDoc;
19 import java.util.Map JavaDoc;
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 JavaDoc;
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 JavaDoc uri;
37     private Map JavaDoc templates = new HashMap JavaDoc();
38     private TagLibrary parent;
39
40     public DynamicTagLibrary() {
41     }
42
43     public DynamicTagLibrary(String JavaDoc 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 JavaDoc name, final Attributes JavaDoc attributes)
49         throws JellyException {
50
51         return new TagScript(
52             new TagFactory() {
53                 public Tag createTag(String JavaDoc name, Attributes JavaDoc 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 JavaDoc name, Attributes JavaDoc attributes)
62         throws JellyException {
63
64         Object JavaDoc 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 JavaDoc 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 JavaDoc 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 JavaDoc name) {
103         Object JavaDoc 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 JavaDoc 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 JavaDoc getUri() {
131         return uri;
132     }
133
134     public void setUri(String JavaDoc 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 }
156
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