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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 1.3 2004/03/19 20:17:55 maartenc Exp $
7   
8   package org.xml.sax.helpers;
9   
10  import java.lang.reflect.Method;
11  import java.lang.reflect.InvocationTargetException;
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 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", null);
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(), null);
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  }