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Java > Open Source Codes > org > xml > sax > helpers > NewInstance


1 // NewInstance.java - create a new instance of a class by name.
2 // http://www.saxproject.org
3 // Written by Edwin Goei, edwingo@apache.org
4 // and by David Brownell, dbrownell@users.sourceforge.net
5 // NO WARRANTY! This class is in the Public Domain.
6 // $Id: NewInstance.java,v 1.1.24.1 2004/05/01 08:34:46 jsuttor Exp $
7
8 package org.xml.sax.helpers;
9
10 import java.lang.reflect.Method JavaDoc;
11 import java.lang.reflect.InvocationTargetException JavaDoc;
12
13 /**
14  * Create a new instance of a class by name.
15  *
16  * <blockquote>
17  * <em>This module, both source code and documentation, is in the
18  * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
19  * See <a HREF='http://www.saxproject.org'>http://www.saxproject.org</a>
20  * for further information.
21  * </blockquote>
22  *
23  * <p>This class contains a static method for creating an instance of a
24  * class from an explicit class name. It tries to use the thread's context
25  * ClassLoader if possible and falls back to using
26  * Class.forName(String).</p>
27  *
28  * <p>This code is designed to compile and run on JDK version 1.1 and later
29  * including versions of Java 2.</p>
30  *
31  * @author Edwin Goei, David Brownell
32  * @version 2.0.1 (sax2r2)
33  */
34 class NewInstance {
35
36     /**
37      * Creates a new instance of the specified class name
38      *
39      * Package private so this code is not exposed at the API level.
40      */
41     static Object JavaDoc newInstance (ClassLoader JavaDoc classLoader, String JavaDoc className)
42         throws ClassNotFoundException JavaDoc, IllegalAccessException JavaDoc,
43             InstantiationException JavaDoc
44     {
45         Class JavaDoc driverClass;
46         if (classLoader == null) {
47             driverClass = Class.forName(className);
48         } else {
49             driverClass = classLoader.loadClass(className);
50         }
51         return driverClass.newInstance();
52     }
53
54     /**
55      * Figure out which ClassLoader to use. For JDK 1.2 and later use
56      * the context ClassLoader.
57      */
58     static ClassLoader JavaDoc getClassLoader ()
59     {
60         Method JavaDoc m = null;
61
62         try {
63             m = Thread JavaDoc.class.getMethod("getContextClassLoader", null);
64         } catch (NoSuchMethodException JavaDoc e) {
65             // Assume that we are running JDK 1.1, use the current ClassLoader
66 return NewInstance JavaDoc.class.getClassLoader();
67         }
68
69         try {
70             return (ClassLoader JavaDoc) m.invoke(Thread.currentThread(), null);
71         } catch (IllegalAccessException JavaDoc e) {
72             // assert(false)
73 throw new UnknownError JavaDoc(e.getMessage());
74         } catch (InvocationTargetException JavaDoc e) {
75             // assert(e.getTargetException() instanceof SecurityException)
76 throw new UnknownError JavaDoc(e.getMessage());
77         }
78     }
79 }
80
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