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
8package org.xml.sax.helpers;
9
10import java.lang.reflect.InvocationTargetException;
11import 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 */
34class 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 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     */
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