libjava/org/xml/sax/helpers/NewInstance.java

   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
   7 // $Id: NewInstance.java,v 1.1.2.4 2002/01/29 21:34:14 dbrownell Exp $
   8
   9 package org.xml.sax.helpers;
  10
  11 import java.lang.reflect.Method;
  12 import java.lang.reflect.InvocationTargetException;
  13
  14 /**
  15  * Create a new instance of a class by name.
  16  *
  17  * <blockquote>
  18  * <em>This module, both source code and documentation, is in the
  19  * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
  20  * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
  21  * for further information.
  22  * </blockquote>
  23  *
  24  * <p>This class contains a static method for creating an instance of a
  25  * class from an explicit class name.  It tries to use the thread's context
  26  * ClassLoader if possible and falls back to using
  27  * Class.forName(String).</p>
  28  *
  29  * <p>This code is designed to compile and run on JDK version 1.1 and later
  30  * including versions of Java 2.</p>
  31  *
  32  * @author Edwin Goei, David Brownell
  33  * @version 2.0.1 (sax2r2)
  34  */
  35 class NewInstance {
  36
  37     /**
  38      * Creates a new instance of the specified class name
  39      *
  40      * Package private so this code is not exposed at the API level.
  41      */
  42     static Object newInstance (ClassLoader classLoader, String className)
  43         throws ClassNotFoundException, IllegalAccessException,
  44             InstantiationException
  45     {
  46         Class driverClass;
  47         if (classLoader == null) {
  48             driverClass = Class.forName(className);
  49         } else {
  50             driverClass = classLoader.loadClass(className);
  51         }
  52         return driverClass.newInstance();
  53     }
  54
  55     /**
  56      * Figure out which ClassLoader to use.  For JDK 1.2 and later use
  57      * the context ClassLoader.
  58      */
  59     static ClassLoader getClassLoader ()
  60     {
  61         Method m = null;
  62
  63         try {
  64             m = Thread.class.getMethod("getContextClassLoader", null);
  65         } catch (NoSuchMethodException e) {
  66             // Assume that we are running JDK 1.1, use the current ClassLoader
  67             return NewInstance.class.getClassLoader();
  68         }
  69
  70         try {
  71             return (ClassLoader) m.invoke(Thread.currentThread(), null);
  72         } catch (IllegalAccessException e) {
  73             // assert(false)
  74             throw new UnknownError(e.getMessage());
  75         } catch (InvocationTargetException e) {
  76             // assert(e.getTargetException() instanceof SecurityException)
  77             throw new UnknownError(e.getMessage());
  78         }
  79     }
  80 }