1 /*
2 * $Header: /home/cvs/jakarta-commons-sandbox/jelly/src/java/org/apache/commons/jelly/tags/core/ChooseTag.java,v 1.3 2002/05/15 06:25:46 jstrachan Exp $
3 * $Revision: 1.3 $
4 * $Date: 2002/05/15 06:25:46 $
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: ChooseTag.java,v 1.3 2002/05/15 06:25:46 jstrachan Exp $
61 */
62 package org.apache.commons.jelly.tags.core;
63
64 import org.apache.commons.jelly.JellyContext;
65 import org.apache.commons.jelly.MissingAttributeException;
66 import org.apache.commons.jelly.TagSupport;
67 import org.apache.commons.jelly.XMLOutput;
68
69 /*** A tag which creates a new object of the given type
70 *
71 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
72 * @version $Revision: 1.3 $
73 */
74 public class NewTag extends TagSupport {
75
76 /*** the variable exported */
77 private String var;
78
79 /*** the class name of the object to instantiate */
80 private String className;
81
82 /***
83 * The class loader to use for instantiating application objects.
84 * If not specified, the context class loader, or the class loader
85 * used to load XMLParser itself, is used, based on the value of the
86 * <code>useContextClassLoader</code> variable.
87 */
88 protected ClassLoader classLoader = null;
89
90 /***
91 * Do we want to use the Context ClassLoader when loading classes
92 * for instantiating new objects? Default is <code>false</code>.
93 */
94 protected boolean useContextClassLoader = false;
95
96
97 public NewTag() {
98 }
99
100 /*** Sets the name of the variable exported by this tag */
101 public void setVar(String var) {
102 this.var = var;
103 }
104
105 /*** Sets the class name of the object to instantiate */
106 public void setClassName(String className) {
107 this.className = className;
108 }
109
110 /***
111 * Return the class loader to be used for instantiating application objects
112 * when required. This is determined based upon the following rules:
113 * <ul>
114 * <li>The class loader set by <code>setClassLoader()</code>, if any</li>
115 * <li>The thread context class loader, if it exists and the
116 * <code>useContextClassLoader</code> property is set to true</li>
117 * <li>The class loader used to load the XMLParser class itself.
118 * </ul>
119 */
120 public ClassLoader getClassLoader() {
121 if (this.classLoader != null) {
122 return (this.classLoader);
123 }
124 if (this.useContextClassLoader) {
125 ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
126 if (classLoader != null) {
127 return (classLoader);
128 }
129 }
130 return (this.getClass().getClassLoader());
131 }
132
133 /***
134 * Set the class loader to be used for instantiating application objects
135 * when required.
136 *
137 * @param classLoader The new class loader to use, or <code>null</code>
138 * to revert to the standard rules
139 */
140 public void setClassLoader(ClassLoader classLoader) {
141 this.classLoader = classLoader;
142 }
143
144 /***
145 * Return the boolean as to whether the context classloader should be used.
146 */
147 public boolean getUseContextClassLoader() {
148 return useContextClassLoader;
149 }
150
151 /***
152 * Determine whether to use the Context ClassLoader (the one found by
153 * calling <code>Thread.currentThread().getContextClassLoader()</code>)
154 * to resolve/load classes. If not
155 * using Context ClassLoader, then the class-loading defaults to
156 * using the calling-class' ClassLoader.
157 *
158 * @param boolean determines whether to use JellyContext ClassLoader.
159 */
160 public void setUseContextClassLoader(boolean use) {
161 useContextClassLoader = use;
162 }
163
164
165 // Tag interface
166 //-------------------------------------------------------------------------
167 public void doTag(XMLOutput output) throws Exception {
168 if ( var == null ) {
169 throw new MissingAttributeException( "var" );
170 }
171 if ( className == null ) {
172 throw new MissingAttributeException( "className" );
173 }
174 Class theClass = getClassLoader().loadClass( className );
175 Object object = theClass.newInstance();
176 context.setVariable(var, object);
177 }
178 }
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