1 /*
2 * Copyright 2000-2005 Sun Microsystems, Inc. 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
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
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
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