JspClassLoader


1   /*******************************************************************************
2    * Copyright (c) 2006-2007 Cognos Incorporated, IBM Corporation and others
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    * 
8    * Contributors:
9    *     Cognos Incorporated - initial API and implementation
10   *     IBM Corporation - bug fixes and enhancements
11   *******************************************************************************/
12  package org.eclipse.equinox.internal.jsp.jasper;
13  
14  import java.io.IOException  ;
15  import java.net.MalformedURLException  ;
16  import java.net.URL  ;
17  import java.net.URLClassLoader  ;
18  import java.util.*;
19  
20  import org.osgi.framework.Bundle;
21  import org.osgi.framework.Constants;
22  
23  /**
24   * Jasper requires that this class loader be an instance of URLClassLoader.
25   * At runtime it uses the URLClassLoader's getURLs method to find jar files that are in turn searched for TLDs. In a webapp
26   * these jar files would normally be located in WEB-INF/lib. In the OSGi context, this behaviour is provided by returning the
27   * URLs of the jar files contained on the Bundle-ClassPath. Other than jar file tld resources this classloader is not used for
28   * loading classes which should be done by the other contained class loaders.
29   * 
30   * The rest of the ClassLoader is as follows:
31   * 1) Thread-ContextClassLoader (top - parent) -- see ContextFinder
32   * 2) Jasper Bundle
33   * 3) The Bundle referenced at JSPServlet creation
34   */
35  public class JspClassLoader extends URLClassLoader   {
36  
37      private static final Bundle JASPERBUNDLE = Activator.getBundle(org.apache.jasper.servlet.JspServlet.class);
38      private static final ClassLoader   PARENT = JspClassLoader.class.getClassLoader().getParent();
39      private static final String   JAVA_PACKAGE = "java.";  //$NON-NLS-1$
40      private static final ClassLoader   EMPTY_CLASSLOADER = new ClassLoader  () {
41          public URL   getResource(String   name) {
42              return null;
43          }
44          public Enumeration findResources(String   name) throws IOException   {
45              return new Enumeration() {
46                  public boolean hasMoreElements() {
47                      return false;
48                  }
49                  public Object   nextElement() {
50                      return null;
51                  }               
52              };
53          }
54          public Class   loadClass(String   name) throws ClassNotFoundException   {
55              throw new ClassNotFoundException  (name);
56          }       
57      };
58  
59      public JspClassLoader(Bundle bundle) {
60          super(new URL  [0], new BundleProxyClassLoader(bundle, new BundleProxyClassLoader(JASPERBUNDLE, new JSPContextFinder(EMPTY_CLASSLOADER))));
61          addBundleClassPathJars(bundle);
62          Bundle[] fragments = Activator.getFragments(bundle);
63          if (fragments != null) {
64              for (int i = 0; i < fragments.length; i++) {
65                  addBundleClassPathJars(fragments[i]);
66              }
67          }       
68      }
69  
70      private void addBundleClassPathJars(Bundle bundle) {
71          Dictionary headers = bundle.getHeaders();
72          String   classPath = (String  ) headers.get(Constants.BUNDLE_CLASSPATH);
73          if (classPath != null) {
74              StringTokenizer tokenizer = new StringTokenizer(classPath, ","); //$NON-NLS-1$
75              while (tokenizer.hasMoreTokens()) {
76                  String   candidate = tokenizer.nextToken().trim();
77                  if (candidate.endsWith(".jar")) { //$NON-NLS-1$
78                      URL   entry = bundle.getEntry(candidate);
79                      if (entry != null) {
80                          URL   jarEntryURL;
81                          try {
82                              jarEntryURL = new URL  ("jar:" + entry.toString() + "!/"); //$NON-NLS-1$ //$NON-NLS-2$
83                              super.addURL(jarEntryURL);
84                          } catch (MalformedURLException   e) {
85                              // TODO should log this.
86                          }
87                      }
88                  }
89              }
90          }
91      }
92  
93      protected Class   loadClass(String   name, boolean resolve) throws ClassNotFoundException   {
94          if (PARENT != null && name.startsWith(JAVA_PACKAGE))
95              return PARENT.loadClass(name);
96          return super.loadClass(name, resolve);
97      }
98  
99      // Classes should "not" be loaded by this classloader from the URLs - it is just used for TLD resource discovery.
100     protected Class   findClass(String   name) throws ClassNotFoundException   {
101         throw new ClassNotFoundException  (name);
102     }
103 }
104
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