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Java > Open Source Codes > org > apache > commons > jelly > tags > core > BaseClassLoaderTag


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.tags.core;
17
18 import org.apache.commons.jelly.TagSupport;
19 import org.apache.commons.jelly.util.ClassLoaderUtils;
20
21 /** Abstract base tag providing {@link ClassLoader} support.
22   *
23   * @author <a HREF="mailto:jstrachan@apache.org">James Strachan</a>
24   * @author Rodney Waldhoff
25   * @version $Revision: 155420 $
26   */
27 public abstract class BaseClassLoaderTag extends TagSupport {
28     /**
29      * The class loader to use for instantiating application objects.
30      * If not specified, the context class loader, or the class loader
31      * used to load XMLParser itself, is used, based on the value of the
32      * <code>useContextClassLoader</code> variable.
33      */
34     protected ClassLoader JavaDoc classLoader = null;
35
36     /**
37      * Do we want to use the Context ClassLoader when loading classes
38      * for instantiating new objects? Default is <code>false</code>.
39      */
40     protected boolean useContextClassLoader = false;
41
42     /**
43      * Return the class loader to be used for instantiating application objects
44      * when required. This is determined based upon the following rules:
45      * <ul>
46      * <li>The class loader set by <code>setClassLoader()</code>, if any</li>
47      * <li>The thread context class loader, if it exists and the
48      * <code>useContextClassLoader</code> property is set to true</li>
49      * <li>The class loader used to load the XMLParser class itself.
50      * </ul>
51      */
52     public ClassLoader JavaDoc getClassLoader() {
53         return ClassLoaderUtils.getClassLoader(classLoader, useContextClassLoader, getClass());
54     }
55
56     /**
57      * Set the class loader to be used for instantiating application objects
58      * when required.
59      *
60      * @param classLoader The new class loader to use, or <code>null</code>
61      * to revert to the standard rules
62      */
63     public void setClassLoader(ClassLoader JavaDoc classLoader) {
64         this.classLoader = classLoader;
65     }
66
67     /**
68      * Return the boolean as to whether the context classloader should be used.
69      */
70     public boolean getUseContextClassLoader() {
71         return useContextClassLoader;
72     }
73
74     /**
75      * Determine whether to use the Context ClassLoader (the one found by
76      * calling <code>Thread.currentThread().getContextClassLoader()</code>)
77      * to resolve/load classes. If not
78      * using Context ClassLoader, then the class-loading defaults to
79      * using the calling-class' ClassLoader.
80      *
81      * @param boolean determines whether to use JellyContext ClassLoader.
82      */
83     public void setUseContextClassLoader(boolean use) {
84         useContextClassLoader = use;
85     }
86 }
87
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