JClassLoader


1   /**
2    * JOnAS: Java(TM) Open Application Server
3    * Copyright (C) 1999-2005 Bull S.A.
4    * Contact: jonas-team@objectweb.org
5    *
6    * This library is free software; you can redistribute it and/or
7    * modify it under the terms of the GNU Lesser General Public
8    * License as published by the Free Software Foundation; either
9    * version 2.1 of the License, or any later version.
10   *
11   * This library is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   * Lesser General Public License for more details.
15   *
16   * You should have received a copy of the GNU Lesser General Public
17   * License along with this library; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
19   * USA
20   *
21   * --------------------------------------------------------------------------
22   * $Id: JClassLoader.java,v 1.12 2005/04/22 13:45:57 benoitf Exp $
23   * --------------------------------------------------------------------------
24   */
25  
26  package org.objectweb.jonas.server;
27  
28  import java.io.File  ;
29  import java.net.URL  ;
30  import java.net.URLClassLoader  ;
31  
32  /**
33   * This class implements a URLClassLoader, that permits to add some URLs in it.
34   * @author Ludovic Bert
35   * @author Florent Benoit
36   */
37  public class JClassLoader extends URLClassLoader   {
38  
39      /**
40       * JClassLoader name
41       */
42      private String   name = null;
43  
44      /**
45       * Need to recompute toString() value ? (urls have changed)
46       * True by default (not done).
47       * Then, compute is done only when required and if needed
48       */
49      private boolean recomputeToString = true;
50  
51      /**
52       * Need to recompute getClassPath() value ? (urls have changed)
53       * True by default (not done).
54       * Then, compute is done only when required and if needed
55       */
56      private boolean recomputeClassPath = true;
57  
58      /**
59       * String representation used by toString() method
60       */
61      private String   toStringValue = null;
62  
63      /**
64       * Classpath value
65       */
66      private String   classpath = null;
67  
68      /**
69       * Constructs a new ClassLoader with the specified URLs.
70       * @param name ClassLoader name (used for Display)
71       * @param urls the URLs to add at the ClassLoader creation.
72       * @param parent parent ClassLoader, null if no parent.
73       */
74      public JClassLoader(String   name, URL  [] urls, ClassLoader   parent) {
75          super(urls, parent);
76          this.name = name;
77          this.recomputeToString = true;
78          this.recomputeClassPath = true;
79      }
80  
81      /**
82       * Constructs a new ClassLoader with the specified URLs.
83       * Uses the default delegation parent classloader.
84       * @param name ClassLoader name (used for Display)
85       * @param urls the URLs to add at the ClassLoader creation.
86       */
87      public JClassLoader(String   name, URL  [] urls) {
88          super(urls);
89          this.name = name;
90          this.recomputeToString = true;
91          this.recomputeClassPath = true;
92      }
93  
94      /**
95       * Add the specified URL to this ClassLoader.
96       * @param url the URL to add to this ClassLoader.
97       */
98      public void addURL(URL   url) {
99          if (url != null) {
100             super.addURL(url);
101         }
102         this.recomputeToString = true;
103         this.recomputeClassPath = true;
104     }
105 
106     /**
107      * Add the specified URLs to this ClassLoader.
108      * @param urls the URLs to add to this ClassLoader.
109      */
110     public void addURLs(URL  [] urls) {
111         if (urls != null) {
112             for (int i = 0; i < urls.length; i++) {
113                 if (urls[i] != null) {
114                     super.addURL(urls[i]);
115                 }
116             }
117         }
118         this.recomputeToString = true;
119         this.recomputeClassPath = true;
120     }
121 
122     /**
123      * Display all the URLs from the class loader
124      */
125     public void printURLs() {
126         System.out.println(name  + " ClassLoader :");
127         URL  [] urls = super.getURLs();
128         for (int i = 0; i < urls.length; i++) {
129             System.out.println("url=" + (new File  (urls[i].getFile())).getAbsolutePath());
130         }
131         // display parent classloader
132         if (getParent() != null && getParent() instanceof JClassLoader) {
133             System.out.println("parent :");
134             ((JClassLoader) getParent()).printURLs();
135         }
136     }
137 
138     /**
139      * Get the class path of this classloader
140      * @return the class path of this classloader
141      */
142     public String   getClassPath() {
143         // urls have changed, need to build value
144         if (recomputeClassPath) {
145             computeClassPath();
146         }
147         return classpath;
148     }
149 
150     /**
151      * Displays useful information
152      * @return information
153      */
154     public String   toString() {
155         // urls have changed, need to build value
156         if (recomputeToString) {
157             computeToString();
158         }
159         return toStringValue;
160     }
161 
162     /**
163      * Compute a string representation used by toString() method
164      */
165     private void computeToString() {
166         StringBuffer   sb = new StringBuffer  ();
167         sb.append(this.getClass().getName());
168         sb.append("[");
169         sb.append(name);
170         sb.append(", urls=");
171         URL  [] urls = getURLs();
172         for (int u = 0; u < urls.length; u++) {
173             sb.append(urls[u]);
174             if (u != urls.length - 1) {
175                 sb.append(";");
176             }
177         }
178         sb.append("]");
179         toStringValue = sb.toString();
180 
181         // value is updated, no need to do it again.
182         recomputeToString = false;
183    }
184 
185     /**
186      * Compute classpath value
187      */
188     private void computeClassPath() {
189         String   cp = "";
190         // add parent classpath before
191         if (getParent() != null && getParent() instanceof JClassLoader) {
192             cp += ((JClassLoader) getParent()).getClassPath();
193         }
194         URL  [] urls = super.getURLs();
195         for (int i = 0; i < urls.length; i++) {
196             cp = cp + File.pathSeparator + (new File  (urls[i].getFile())).getAbsolutePath();
197         }
198         classpath = cp;
199         // update value
200         recomputeClassPath = false;
201     }
202 
203 
204 }
205
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