1 /*
   2  * Copyright (c) 1999, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.jndi.ldap;
  27 
  28 import java.net.MalformedURLException;
  29 import java.net.URL;
  30 
  31 abstract class VersionHelper {
  32 
  33     private static VersionHelper helper = null;
  34 
  35     VersionHelper() {} // Disallow anyone from creating one of these.
  36 
  37     static {
  38         try {
  39             Class.forName("java.net.URLClassLoader"); // 1.2 test
  40             Class.forName("java.security.PrivilegedAction"); // 1.2 test
  41             helper = (VersionHelper)
  42                 Class.forName(
  43                     "com.sun.jndi.ldap.VersionHelper12").newInstance();
  44         } catch (Exception e) {
  45         }
  46 
  47         // Use 1.1 helper if 1.2 test fails, or if we cannot create 1.2 helper
  48         if (helper == null) {
  49             try {
  50                 helper = (VersionHelper)
  51                     Class.forName(
  52                         "com.sun.jndi.ldap.VersionHelper11").newInstance();
  53             } catch (Exception e) {
  54                 // should never happen
  55             }
  56         }
  57     }
  58 
  59     static VersionHelper getVersionHelper() {
  60         return helper;
  61     }
  62 
  63     abstract ClassLoader getURLClassLoader(String[] url)
  64         throws MalformedURLException;
  65 
  66 
  67     static protected URL[] getUrlArray(String[] url) throws MalformedURLException {
  68         URL[] urlArray = new URL[url.length];
  69         for (int i = 0; i < urlArray.length; i++) {
  70             urlArray[i] = new URL(url[i]);
  71         }
  72         return urlArray;
  73     }
  74 
  75     abstract Class<?> loadClass(String className) throws ClassNotFoundException;
  76 
  77     abstract Thread createThread(Runnable r);
  78 }