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 1.4 2002/01/30 20:52:27 dbrownell Exp $
7 
8 package org.xml.sax.helpers;
9 
10 import java.lang.reflect.InvocationTargetException;
11 import java.lang.reflect.Method;
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      */
newInstance(ClassLoader classLoader, String className)41     static Object newInstance (ClassLoader classLoader, String className)
42         throws ClassNotFoundException, IllegalAccessException,
43             InstantiationException
44     {
45         Class 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      */
getClassLoader()58     static ClassLoader getClassLoader ()
59     {
60         Method m = null;
61 
62         try {
63             m = Thread.class.getMethod("getContextClassLoader");
64         } catch (NoSuchMethodException e) {
65             // Assume that we are running JDK 1.1, use the current ClassLoader
66             return NewInstance.class.getClassLoader();
67         }
68 
69         try {
70             return (ClassLoader) m.invoke(Thread.currentThread());
71         } catch (IllegalAccessException e) {
72             // assert(false)
73             throw new UnknownError(e.getMessage());
74         } catch (InvocationTargetException e) {
75             // assert(e.getTargetException() instanceof SecurityException)
76             throw new UnknownError(e.getMessage());
77         }
78     }
79 }
80