ClassLoaderDelegate


1   /*******************************************************************************
2    * Copyright (c) 2004, 2005 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    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  
12  package org.eclipse.osgi.framework.adaptor;
13  
14  import java.io.IOException  ;
15  import java.net.URL  ;
16  import java.util.Enumeration  ;
17  
18  /**
19   * A ClassLoaderDelegate is used by the BundleClassLoader in a similar
20   * fashion that a parent ClassLoader is used.  A ClassLoaderDelegate must
21   * be queried for any resource or class before it is loaded by the 
22   * BundleClassLoader.  The Framework implements the ClassLoaderDelegate
23   * and supplies it to the BundleClassLoader.  FrameworkAdaptor implementations
24   * are not responsible for suppling an implementation for ClassLoaderDelegate.
25   * <p>
26   * This interface is not intended to be implemented by clients.
27   * </p>
28   * @since 3.1
29   */
30  public interface ClassLoaderDelegate {
31      /**
32       * Finds a class for a bundle that may be outside of the actual bundle
33       * (i.e. a class from an imported package or required bundle).<p>
34       * 
35       * If the class does not belong to an imported package or is not 
36       * found in a required bundle then the ClassloaderDelegate will call 
37       * BundleClassLoader.findLocalClass(). <p>
38       *   
39       * If no class is found then a ClassNotFoundException is thrown.
40       * @param classname the class to find. 
41       * @return the Class.
42       * @throws ClassNotFoundException if the class is not found.
43       */
44      public Class   findClass(String   classname) throws ClassNotFoundException  ;
45  
46      /**
47       * Finds a resource for a bundle that may be outside of the actual bundle
48       * (i.e. a resource from an imported package or required bundle).<p>
49       * 
50       * If the resource does not belong to an imported package or is not 
51       * found in a required bundle then the ClassloaderDelegate will call 
52       * BundleClassLoader.findLocalResource(). <p>
53       * 
54       * If no resource is found then return null.
55       * @param resource the resource to load.
56       * @return the resource or null if resource is not found.
57       */
58      public URL   findResource(String   resource);
59  
60      /**
61       * Finds an enumeration of resources for a bundle that may be outside of 
62       * the actual bundle (i.e. a resource from an imported package or required 
63       * bundle).<p>
64       * 
65       * If the resource does not belong to an imported package or is not 
66       * found in a required bundle then the ClassloaderDelegate will call 
67       * BundleClassLoader.findLocalResource(). <p>
68       * If no resource is found then return null.
69       * @param resource the resource to find.
70       * @return the enumeration of resources found or null if the resource
71       * does not exist.
72       */
73      public Enumeration   findResources(String   resource) throws IOException  ;
74  
75      /**
76       * Returns the absolute path name of a native library.  The following is
77       * a list of steps that a ClassLoaderDelegate must take when trying to 
78       * find a library:
79       * <ul>
80       * <li>If the bundle is a fragment then try to find the library in the
81       * host bundle.
82       * <li>if the bundle is a host then try to find the library in the
83       * host bundle and then try to find the library in the fragment
84       * bundles.
85       * </ul>
86       * If no library is found return null.
87       * @param libraryname the library to find the path to.
88       * @return the path to the library or null if not found.
89       */
90      public String   findLibrary(String   libraryname);
91  
92  }
93
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