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1   /*
2    * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
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7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24   */
25  
26  // SAX entity resolver.
27  // http://www.saxproject.org
28  // No warranty; no copyright -- use this as you will.
29  // $Id: EntityResolver.java,v 1.2 2004/11/03 22:44:52 jsuttor Exp $
30  
31  package org.xml.sax;
32  
33  import java.io.IOException;
34  
35  
36  /**
37   * Basic interface for resolving entities.
38   *
39   * <blockquote>
40   * <em>This module, both source code and documentation, is in the
41   * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
42   * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>;
43   * for further information.
44   * </blockquote>
45   *
46   * <p>If a SAX application needs to implement customized handling
47   * for external entities, it must implement this interface and
48   * register an instance with the SAX driver using the
49   * {@link org.xml.sax.XMLReader#setEntityResolver setEntityResolver}
50   * method.</p>
51   *
52   * <p>The XML reader will then allow the application to intercept any
53   * external entities (including the external DTD subset and external
54   * parameter entities, if any) before including them.</p>
55   *
56   * <p>Many SAX applications will not need to implement this interface,
57   * but it will be especially useful for applications that build
58   * XML documents from databases or other specialised input sources,
59   * or for applications that use URI types other than URLs.</p>
60   *
61   * <p>The following resolver would provide the application
62   * with a special character stream for the entity with the system
63   * identifier "http://www.myhost.com/today":</p>
64   *
65   * <pre>
66   * import org.xml.sax.EntityResolver;
67   * import org.xml.sax.InputSource;
68   *
69   * public class MyResolver implements EntityResolver {
70   *   public InputSource resolveEntity (String publicId, String systemId)
71   *   {
72   *     if (systemId.equals("http://www.myhost.com/today")) {
73   *              // return a special input source
74   *       MyReader reader = new MyReader();
75   *       return new InputSource(reader);
76   *     } else {
77   *              // use the default behaviour
78   *       return null;
79   *     }
80   *   }
81   * }
82   * </pre>
83   *
84   * <p>The application can also use this interface to redirect system
85   * identifiers to local URIs or to look up replacements in a catalog
86   * (possibly by using the public identifier).</p>
87   *
88   * @since SAX 1.0
89   * @author David Megginson
90   * @see org.xml.sax.XMLReader#setEntityResolver
91   * @see org.xml.sax.InputSource
92   */
93  public interface EntityResolver {
94  
95  
96      /**
97       * Allow the application to resolve external entities.
98       *
99       * <p>The parser will call this method before opening any external
100      * entity except the top-level document entity.  Such entities include
101      * the external DTD subset and external parameter entities referenced
102      * within the DTD (in either case, only if the parser reads external
103      * parameter entities), and external general entities referenced
104      * within the document element (if the parser reads external general
105      * entities).  The application may request that the parser locate
106      * the entity itself, that it use an alternative URI, or that it
107      * use data provided by the application (as a character or byte
108      * input stream).</p>
109      *
110      * <p>Application writers can use this method to redirect external
111      * system identifiers to secure and/or local URIs, to look up
112      * public identifiers in a catalogue, or to read an entity from a
113      * database or other input source (including, for example, a dialog
114      * box).  Neither XML nor SAX specifies a preferred policy for using
115      * public or system IDs to resolve resources.  However, SAX specifies
116      * how to interpret any InputSource returned by this method, and that
117      * if none is returned, then the system ID will be dereferenced as
118      * a URL.  </p>
119      *
120      * <p>If the system identifier is a URL, the SAX parser must
121      * resolve it fully before reporting it to the application.</p>
122      *
123      * @param publicId The public identifier of the external entity
124      *        being referenced, or null if none was supplied.
125      * @param systemId The system identifier of the external entity
126      *        being referenced.
127      * @return An InputSource object describing the new input source,
128      *         or null to request that the parser open a regular
129      *         URI connection to the system identifier.
130      * @exception org.xml.sax.SAXException Any SAX exception, possibly
131      *            wrapping another exception.
132      * @exception java.io.IOException A Java-specific IO exception,
133      *            possibly the result of creating a new InputStream
134      *            or Reader for the InputSource.
135      * @see org.xml.sax.InputSource
136      */
137     public abstract InputSource resolveEntity (String publicId,
138                                                String systemId)
139         throws SAXException, IOException;
140 
141 }
142 
143 // end of EntityResolver.java