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// NewInstance.java - create a new instance of a class by name.
// http://www.saxproject.org
// Written by Edwin Goei, edwingo@apache.org
// and by David Brownell, dbrownell@users.sourceforge.net
// NO WARRANTY! This class is in the Public Domain.
// $Id: NewInstance.java 670297 2008-06-22 01:57:58Z mrglavas $
package org.xml.sax.helpers;
/**
* Create a new instance of a class by name.
*
* <blockquote>
* <em>This module, both source code and documentation, is in the
* Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
* See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
* for further information.
* </blockquote>
*
* <p>This class contains a static method for creating an instance of a
* class from an explicit class name. It tries to use the thread's context
* ClassLoader if possible and falls back to using
* Class.forName(String). It also takes into account JDK 1.2+'s
* AccessController mechanism for performing its actions. </p>
*
* <p>This code is designed to compile and run on JDK version 1.1 and later
* including versions of Java 2.</p>
*
* <p>This is <strong>not</strong> the NewInstance accompanying SAX 2.0.2; it
* represents many fixes to that code.
*
* @author Edwin Goei, David Brownell
* @version 2.0.1 (sax2r2)
*/
class NewInstance {
// constants
// governs whether, if we fail in finding a class even
// when given a classloader, we'll make a last-ditch attempt
// to use the current classloader.
private static final boolean DO_FALLBACK = true;
/**
* Creates a new instance of the specified class name
*
* Package private so this code is not exposed at the API level.
*/
static Object newInstance (ClassLoader classLoader, String className)
throws ClassNotFoundException, IllegalAccessException,
InstantiationException
{
Class driverClass;
if (classLoader == null) {
// XXX Use the bootstrap ClassLoader. There is no way to
// load a class using the bootstrap ClassLoader that works
// in both JDK 1.1 and Java 2. However, this should still
// work b/c the following should be true:
//
// (cl == null) iff current ClassLoader == null
//
// Thus Class.forName(String) will use the current
// ClassLoader which will be the bootstrap ClassLoader.
driverClass = Class.forName(className);
} else {
try {
driverClass = classLoader.loadClass(className);
} catch (ClassNotFoundException x) {
if (DO_FALLBACK) {
// Fall back to current classloader
classLoader = NewInstance.class.getClassLoader();
if (classLoader != null) {
driverClass = classLoader.loadClass(className);
}
else {
driverClass = Class.forName(className);
}
} else {
throw x;
}
}
}
Object instance = driverClass.newInstance();
return instance;
}
/**
* Figure out which ClassLoader to use. For JDK 1.2 and later use
* the context ClassLoader.
*/
static ClassLoader getClassLoader ()
{
// Figure out which ClassLoader to use for loading the provider
// class. If there is a Context ClassLoader then use it.
ClassLoader cl = SecuritySupport.getContextClassLoader();
if (cl == null) {
// Assert: we are on JDK 1.1 or we have no Context ClassLoader
// so use the current ClassLoader
cl = NewInstance.class.getClassLoader();
}
return cl;
}
}
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