ClassUtils


1   /**
2    * $RCSfile: ClassUtils.java,v $
3    * $Revision: 1.3 $
4    * $Date: 2004/11/09 18:37:52 $
5    *
6    * Copyright (C) 2004 Jive Software. All rights reserved.
7    *
8    * This software is published under the terms of the GNU Public License (GPL),
9    * a copy of which is included in this distribution.
10   */
11  package org.jivesoftware.util;
12  
13  import java.io.InputStream  ;
14  
15  /**
16   * A utility class to assist with loading classes or resources by name. Many application servers use
17   * custom classloaders, which will break uses of:
18   * <pre>
19   *    Class.forName(className);
20   * </pre>
21   *
22   * This utility attempts to load the class or resource using a number of different mechanisms to
23   * work around this problem.
24   *
25   * @author Matt Tucker
26   */
27  public class ClassUtils {
28  
29      private static ClassUtils instance = new ClassUtils();
30  
31      /**
32       * Loads the class with the specified name.
33       *
34       * @param className the name of the class
35       * @return the resulting <code>Class</code> object
36       * @throws ClassNotFoundException if the class was not found
37       */
38      public static Class   forName(String   className) throws ClassNotFoundException   {
39          return instance.loadClass(className);
40      }
41  
42      /**
43       * Loads the given resource as a stream.
44       *
45       * @param name the name of the resource that exists in the classpath.
46       * @return the resource as an input stream or <tt>null</tt> if the resource was not found.
47       */
48      public static InputStream   getResourceAsStream(String   name) {
49          return instance.loadResource(name);
50      }
51  
52      /**
53       * Not instantiatable.
54       */
55      private ClassUtils() {}
56  
57      public Class   loadClass(String   className) throws ClassNotFoundException   {
58          Class   theClass = null;
59          try {
60              theClass = Class.forName(className);
61          }
62          catch (ClassNotFoundException   e1) {
63              try {
64                  theClass = Thread.currentThread().getContextClassLoader().loadClass(className);
65              }
66              catch (ClassNotFoundException   e2) {
67                  theClass = getClass().getClassLoader().loadClass(className);
68              }
69          }
70          return theClass;
71      }
72  
73      private InputStream   loadResource(String   name) {
74          InputStream   in = getClass().getResourceAsStream(name);
75          if (in == null) {
76              in = Thread.currentThread().getContextClassLoader().getResourceAsStream(name);
77              if (in == null) {
78                  in = getClass().getClassLoader().getResourceAsStream(name);
79              }
80          }
81          return in;
82      }
83  }
84
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