URLPolicy


1   /*
2    * ModuleLoader - A generic, policy-driven class loader.
3    * Copyright (c) 2004, Richard S. Hall
4    * All rights reserved.
5    *
6    * Redistribution and use in source and binary forms, with or without
7    * modification, are permitted provided that the following conditions
8    * are met:
9    *
10   *   * Redistributions of source code must retain the above copyright
11   *     notice, this list of conditions and the following disclaimer.
12   *   * Redistributions in binary form must reproduce the above copyright
13   *     notice, this list of conditions and the following disclaimer in
14   *     the documentation and/or other materials provided with the
15   *     distribution.
16   *   * Neither the name of the ungoverned.org nor the names of its
17   *     contributors may be used to endorse or promote products derived
18   *     from this software without specific prior written permission.
19   *
20   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31   *
32   * Contact: Richard S. Hall (heavy@ungoverned.org)
33   * Contributor(s):
34   *
35  **/
36  package org.ungoverned.moduleloader;
37  
38  import java.net.URL  ;
39  
40  /**
41   * <p>
42   * This interface represents the <tt>ModuleLoader</tt>'s policy for creating
43   * <tt>URL</tt> for resource loading and security purposes. Java requires the
44   * use of <tt>URL</tt>s for resource loading and security. For resource loading,
45   * <tt>URL</tt>s are returned for requested resources. Subsequently, the resource
46   * <tt>URL</tt> is used to create an input stream for reading the resources
47   * bytes. With respect to security, <tt>URL</tt>s are used when defining a
48   * class in order to determine where the code came from, this concept is called
49   * a <tt>CodeSource</tt>. This approach enables Java to assign permissions to
50   * code that originates from particular locations.
51   * </p>
52   * <p>
53   * The <tt>ModuleManager</tt> requires a concrete implementation of this
54   * interface in order to function. Whenever the <tt>ModuleManager</tt> requires
55   * a <tt>URL</tt> for either resource loading or security, it delegates to
56   * the policy implementation. A default implementation is provided,
57   * called <a HREF="DefaultURLPolicy.html"><tt>DefaultURLPolicy</tt></a>, but
58   * it only supports resource loading, not security.
59   * </p>
60   * @see org.ungoverned.moduleloader.ModuleManager
61   * @see org.ungoverned.moduleloader.DefaultURLPolicy
62  **/
63  public interface URLPolicy
64  {
65      /**
66       * <p>
67       * This method should return a <tt>URL</tt> that represents the
68       * location from which the module originated. This <tt>URL</tt>
69       * can be used when assigning permissions to the module, such as
70       * is done in the Java permissions policy file.
71       * </p>
72       * @param mgr the <tt>ModuleManager</tt> of the module.
73       * @param module the module for which the <tt>URL</tt> is to be created.
74       * @return an <tt>URL</tt> to associate with the module.
75      **/
76      public URL   createCodeSourceURL(ModuleManager mgr, Module module);
77  
78      /**
79       * <p>
80       * This method should return a <tt>URL</tt> that is suitable
81       * for accessing the bytes of the specified resource. It must be possible
82       * open a connection to this <tt>URL</tt>, which may require that
83       * the implementer of this method also introduce a custom
84       * <tt>java.net.URLStreamHander</tt> when creating the <tt>URL</tt>.
85       * </p>
86       * @param mgr the <tt>ModuleManager</tt> of the module.
87       * @param module the module for which the resource is being loaded.
88       * @param rsIdx the index of the <tt>ResourceSource</tt> containing the resource.
89       * @param name the name of the resource being loaded.
90       * @return an <tt>URL</tt> for retrieving the resource.
91      **/
92      public URL   createResourceURL(ModuleManager mgr, Module module, int rsIdx, String   name);
93  }
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