1 /*
2 * $Header: /home/cvs/jakarta-commons-sandbox/jelly/src/java/org/apache/commons/jelly/TagLibrary.java,v 1.13 2002/09/05 16:43:29 jstrachan Exp $
3 * $Revision: 1.13 $
4 * $Date: 2002/09/05 16:43:29 $
5 *
6 * ====================================================================
7 *
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 1999-2002 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution, if
26 * any, must include the following acknowlegement:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowlegement may appear in the software itself,
30 * if and wherever such third-party acknowlegements normally appear.
31 *
32 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
33 * Foundation" must not be used to endorse or promote products derived
34 * from this software without prior written permission. For written
35 * permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache"
38 * nor may "Apache" appear in their names without prior written
39 * permission of the Apache Group.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>.
59 *
60 * $Id: TagLibrary.java,v 1.13 2002/09/05 16:43:29 jstrachan Exp $
61 */
62
63 package org.apache.commons.jelly;
64
65 import java.util.HashMap;
66 import java.util.Map;
67
68 import org.apache.commons.jelly.expression.CompositeExpression;
69 import org.apache.commons.jelly.expression.ConstantExpression;
70 import org.apache.commons.jelly.expression.Expression;
71 import org.apache.commons.jelly.expression.ExpressionFactory;
72 import org.apache.commons.jelly.impl.TagScript;
73
74 import org.xml.sax.Attributes;
75
76 /*** <p><code>Taglib</code> represents the metadata for a Jelly custom tag library.</p>
77 *
78 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
79 * @version $Revision: 1.13 $
80 */
81
82 public abstract class TagLibrary {
83
84 private Map tags = new HashMap();
85
86 public TagLibrary() {
87
88 }
89
90 /*** Creates a new script to execute the given tag name and attributes */
91 public TagScript createTagScript(String name, Attributes attributes)
92 throws Exception {
93
94 Class type = (Class) tags.get(name);
95 if ( type != null ) {
96 return TagScript.newInstance(type);
97 }
98 return null;
99
100 }
101
102 /*** Creates a new Tag for the given tag name and attributes */
103 public Tag createTag(String name, Attributes attributes)
104 throws Exception {
105
106 Class type = (Class) tags.get(name);
107 if ( type != null ) {
108 return (Tag) type.newInstance();
109 }
110 return null;
111
112 }
113
114
115 /*** Allows taglibs to use their own expression evaluation mechanism */
116 public Expression createExpression(
117 ExpressionFactory factory,
118 String tagName,
119 String attributeName,
120 String attributeValue)
121 throws Exception {
122
123 ExpressionFactory myFactory = getExpressionFactory();
124 if (myFactory == null) {
125 myFactory = factory;
126 }
127 if (myFactory != null) {
128 return CompositeExpression.parse(attributeValue, myFactory);
129 }
130
131 // will use a constant expression instead
132 return new ConstantExpression(attributeValue);
133 }
134
135
136 // Implementation methods
137 //-------------------------------------------------------------------------
138
139 /*** Registers a tag class for a given tag name */
140 protected void registerTag(String name, Class type) {
141 tags.put(name, type);
142 }
143
144 /*** Allows derived tag libraries to use their own factory */
145 protected ExpressionFactory getExpressionFactory() {
146 return null;
147 }
148
149 protected Map getTagClasses() {
150 return tags;
151 }
152
153 }
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