1 /*
2 * $Header: /u/cvs/Projects/EnhydraOrg/enhydra3x/Enhydra/modules/Tomcat/src/share/org/apache/tomcat/util/Attic/NetworkClassLoader.java,v 1.2.2.1.2.1 2001/02/09 09:53:01 markd Exp $
3 * $Revision: 1.2.2.1.2.1 $
4 * $Date: 2001/02/09 09:53:01 $
5 *
6 * ====================================================================
7 *
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 1999 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution, if
26 * any, must include the following acknowlegement:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowlegement may appear in the software itself,
30 * if and wherever such third-party acknowlegements normally appear.
31 *
32 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
33 * Foundation" must not be used to endorse or promote products derived
34 * from this software without prior written permission. For written
35 * permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache"
38 * nor may "Apache" appear in their names without prior written
39 * permission of the Apache Group.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>.
59 *
60 * [Additional notices, if required by prior licensing conditions]
61 *
62 */
63
64 package org.apache.tomcat.util;
65
66 import java.util.zip;
67 import java.net;
68 import java.util;
69 import java.io;
70
71 /**
72 * The correct name for this class should be URLClassLoader.
73 * But there is already a class by that name in JDK1.2.
74 *
75 * I have had quite a few problems with URLClassLoader in
76 * past, so I ended up writing this ClassLoader. I found that
77 * the Java 2's URLClassLoader, does not close the Jar file once
78 * opened. It is a pretty good optimization step, but if you
79 * modify the class in the jar file, it does not pick it up. Some
80 * operating systems may not let you modify the jar file while it is
81 * still open. IMHO, it does make sense to close the jar file
82 * after you are done reading the class data. But this approach may not
83 * get you the performance of the URLClassLoader, but it works in all
84 * cases and also runs on JDK1.1. I have enhanced this class loader
85 * to read all the zip/jar entries once & cache the data, so that
86 * there is no overhead of opening/closing jar file to pick up
87 * each entry.
88 *
89 *
90 * @author Harish Prabandham
91 */
92 public class NetworkClassLoader extends ClassLoader {
93 private ClassLoader parent = null; // parent classloader
94 private Hashtable classCache = new Hashtable();
95 private Hashtable urlset = new Hashtable();
96
97 /**
98 * Creates a new instance of the class loader.
99 * @param delegate/parent class loader.
100 */
101 public NetworkClassLoader(ClassLoader parent) {
102 setParent(parent);
103 }
104
105 /**
106 * Sets the parent/delegate class loader.
107 * @param delegate/parent class loader.
108 */
109 protected final void setParent(ClassLoader parent) {
110 this.parent = parent;
111 }
112
113 /**
114 * Adds the given URL to this class loader. If the URL
115 * ends with "/", then it is assumed to be a directory
116 * otherwise, it is assumed to be a zip/jar file. If the
117 * same URL is added again, the URL is re-opened and this
118 * zip/jar file is used for serving any future class requests.
119 * @param URL where to look for the classes.
120 */
121 public synchronized void addURL(URL url) {
122 // System.out.println("Adding url: " + url);
123 if(!urlset.containsKey(url)) {
124 try {
125 urlset.put(url, new URLResourceReader(url));
126 }catch(IOException ioe){
127 // Probably a bad url...
128 }
129 } else {
130 // remove the old one & add a new one...
131 try{
132 URLResourceReader newu = new URLResourceReader(url);
133 URLResourceReader oldu = (URLResourceReader) urlset.get(url);
134 oldu.close();
135 urlset.remove(url);
136 urlset.put(url, newu);
137 } catch (IOException ioe) {
138 }
139 }
140 }
141
142 /**
143 * @return An enumeration of URLs where this class loader
144 * looks for classes.
145 */
146 public Enumeration getURLs() {
147 return urlset.keys();
148 }
149
150 private byte[] loadResource(URL url, String resourceName)
151 throws IOException {
152 URLResourceReader urr = (URLResourceReader) urlset.get(url);
153 if(urr != null) {
154 return urr.getResource(resourceName);
155 }
156
157 return null;
158 }
159
160 private byte[] loadResource(String resource) {
161 byte[] barray = null;
162 for(Enumeration e = urlset.keys(); e.hasMoreElements();) {
163 URL url = (URL) e.nextElement();
164
165 try {
166 barray = loadResource(url, resource);
167 } catch(Exception ex) {
168 } finally {
169 if(barray != null)
170 break;
171 }
172 }
173
174 return barray;
175 }
176
177 private byte[] loadClassData(String classname) {
178 String resourceName = classname.replace('.', '/') + ".class";
179 return loadResource(resourceName);
180 }
181
182 /**
183 * @return The resource as the input stream if such a resource
184 * exists, otherwise returns null.
185 */
186 public InputStream getResourceAsStream(String name) {
187 InputStream istream = null;
188
189 // Algorithm:
190 //
191 // 1. first check the system path for the resource
192 // 2. next check the delegate/parent class loader for the resource
193 // 3. then attempt to get the resource from the url set.
194 //
195
196 // Lets check the system path for the resource.
197 istream = getSystemResourceAsStream(name);
198 if(istream != null)
199 return istream;
200
201 // Lets check the parent/delegate class loader for the resource.
202 if(parent != null) {
203 istream = parent.getResourceAsStream(name);
204 if(istream != null)
205 return istream;
206 }
207
208 // Lets load it ourselves.
209 byte[] data = loadResource(name);
210 if(data != null) {
211 istream = new ByteArrayInputStream(data);
212 }
213
214 return istream;
215 }
216
217 /**
218 * java.lang.ClassLoader's defineClass method is final, so the
219 * its subclasses cannot override this method. But, this class
220 * calls this method in the loadClass() instead.
221 * @param The name of the class without ".class" extension.
222 * @param The class data bytes.
223 * @return The class object.
224 */
225 protected Class defineClass(String classname, byte[] classdata) {
226 return defineClass(classname, classdata, 0, classdata.length);
227 }
228
229 protected synchronized Class loadClass(String name, boolean resolve)
230 throws ClassNotFoundException {
231 Class c = null;
232
233 // Algorithm: (Please do not change the order; unless you
234 // have a good reason to do so).
235 //
236 // 1. first check the system class loader.
237 // 2. next check the delegate/parent class loader.
238 // 3. next check the class cache
239 // 4. then attempt to load classes from the URL set.
240 //
241
242 // Lets see if the class is in system class loader.
243 try {
244 c = findSystemClass(name);
245 }catch(ClassNotFoundException cnfe) {
246 }finally {
247 if(c != null)
248 return c;
249 }
250
251 // Lets see if the class is in parent class loader.
252 try {
253 if(parent != null)
254 c = parent.loadClass(name);
255 }catch(ClassNotFoundException cnfe) {
256 }finally {
257 if(c != null)
258 return c;
259 }
260
261 // Lets see if the class is in the cache..
262 c = (Class) classCache.get(name);
263
264 if(c != null)
265 return c;
266
267
268 // Lets see if we find the class all by ourselves.
269 byte[] data = loadClassData(name);
270
271 if(data != null) {
272 // we did !!
273 c = defineClass(name, data);
274 classCache.put(name, c);
275 if(resolve)
276 resolveClass(c);
277 } else {
278 // We are out of luck at this point...
279 throw new ClassNotFoundException(name);
280 }
281
282 return c;
283 }
284
285 /**
286 * This method resets this ClassLoader's state. It completely
287 * removes all the URLs and classes in this class loader cache.
288 */
289 protected final void clear() {
290 urlset.clear();
291 classCache.clear();
292 }
293
294 /**
295 * This method resets this ClassLoader's state and resets the
296 * references for garbage collection.
297 */
298 protected void finalize() throws Throwable {
299 // Cleanup real well. Otherwise, this can be
300 // a major source of memory leaks...
301
302 // remove all the urls & class entries.
303 clear();
304
305 parent = null;
306 urlset = null;
307 classCache = null;
308 }
309
310
311 // Added for enhydra:
312
313 /**
314 * @see ClassLoader#findResource(String)
315 */
316 protected URL findResource(String name) {
317 for(Enumeration e = urlset.keys(); e.hasMoreElements();) {
318 URL url = (URL) e.nextElement();
319
320 try {
321 URL realURL = new URL(url.getProtocol(), url.getHost(),
322 url.getFile() + name);
323 File urlFile = new File(realURL.getFile());
324 if (urlFile.exists()) {
325 return realURL;
326 }
327 } catch (MalformedURLException except) {
328 // Ignore invalid CLASSPATH entries
329 }
330 }
331
332 return null;
333 }
334
335 }
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