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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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