Source code: org/jdom/Namespace.java
1 /*--
2
3 $Id: Namespace.java,v 1.41 2004/02/27 11:32:57 jhunter Exp $
4
5 Copyright (C) 2000-2004 Jason Hunter & Brett McLaughlin.
6 All rights reserved.
7
8 Redistribution and use in source and binary forms, with or without
9 modification, are permitted provided that the following conditions
10 are met:
11
12 1. Redistributions of source code must retain the above copyright
13 notice, this list of conditions, and the following disclaimer.
14
15 2. Redistributions in binary form must reproduce the above copyright
16 notice, this list of conditions, and the disclaimer that follows
17 these conditions in the documentation and/or other materials
18 provided with the distribution.
19
20 3. The name "JDOM" must not be used to endorse or promote products
21 derived from this software without prior written permission. For
22 written permission, please contact <request_AT_jdom_DOT_org>.
23
24 4. Products derived from this software may not be called "JDOM", nor
25 may "JDOM" appear in their name, without prior written permission
26 from the JDOM Project Management <request_AT_jdom_DOT_org>.
27
28 In addition, we request (but do not require) that you include in the
29 end-user documentation provided with the redistribution and/or in the
30 software itself an acknowledgement equivalent to the following:
31 "This product includes software developed by the
32 JDOM Project (http://www.jdom.org/)."
33 Alternatively, the acknowledgment may be graphical using the logos
34 available at http://www.jdom.org/images/logos.
35
36 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
37 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
38 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
39 DISCLAIMED. IN NO EVENT SHALL THE JDOM AUTHORS OR THE PROJECT
40 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
42 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
43 USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
44 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
45 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
46 OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
47 SUCH DAMAGE.
48
49 This software consists of voluntary contributions made by many
50 individuals on behalf of the JDOM Project and was originally
51 created by Jason Hunter <jhunter_AT_jdom_DOT_org> and
52 Brett McLaughlin <brett_AT_jdom_DOT_org>. For more information
53 on the JDOM Project, please see <http://www.jdom.org/>.
54
55 */
56
57 package org.jdom;
58
59 import java.util.*;
60
61 /**
62 * An XML namespace representation, as well as a factory for creating XML
63 * namespace objects. Namespaces are not Serializable, however objects that use
64 * namespaces have special logic to handle serialization manually. These classes
65 * call the getNamespace() method on deserialization to ensure there is one
66 * unique Namespace object for any unique prefix/uri pair.
67 *
68 * @version $Revision: 1.41 $, $Date: 2004/02/27 11:32:57 $
69 * @author Brett McLaughlin
70 * @author Elliotte Rusty Harold
71 * @author Jason Hunter
72 * @author Wesley Biggs
73 */
74 public final class Namespace {
75
76 // XXX May want to use weak references to keep the maps from growing
77 // large with extended use
78
79 // XXX We may need to make the namespaces HashMap synchronized with
80 // reader/writer locks or perhaps make Namespace no longer a flyweight.
81 // As written, multiple put() calls may happen from different threads
82 // concurrently and cause a ConcurrentModificationException. See
83 // http://lists.denveronline.net/lists/jdom-interest/2000-September/003009.html.
84 // No one has ever reported this over the many years, so don't worry yet.
85
86 private static final String CVS_ID =
87 "@(#) $RCSfile: Namespace.java,v $ $Revision: 1.41 $ $Date: 2004/02/27 11:32:57 $ $Name: jdom_1_0 $";
88
89 /**
90 * Factory list of namespaces.
91 * Keys are <i>prefix</i>&<i>URI</i>.
92 * Values are Namespace objects
93 */
94 private static HashMap namespaces;
95
96 /** Define a <code>Namespace</code> for when <i>not</i> in a namespace */
97 public static final Namespace NO_NAMESPACE = new Namespace("", "");
98
99 /** Define a <code>Namespace</code> for the standard xml prefix. */
100 public static final Namespace XML_NAMESPACE =
101 new Namespace("xml", "http://www.w3.org/XML/1998/namespace");
102
103 /** The prefix mapped to this namespace */
104 private String prefix;
105
106 /** The URI for this namespace */
107 private String uri;
108
109 /**
110 * This static initializer acts as a factory contructor.
111 * It sets up storage and required initial values.
112 */
113 static {
114 namespaces = new HashMap();
115
116 // Add the "empty" namespace
117 namespaces.put("&", NO_NAMESPACE);
118 namespaces.put("xml&http://www.w3.org/XML/1998/namespace",
119 XML_NAMESPACE);
120 }
121
122 /**
123 * This will retrieve (if in existence) or create (if not) a
124 * <code>Namespace</code> for the supplied prefix and URI.
125 *
126 * @param prefix <code>String</code> prefix to map to
127 * <code>Namespace</code>.
128 * @param uri <code>String</code> URI of new <code>Namespace</code>.
129 * @return <code>Namespace</code> - ready to use namespace.
130 * @throws IllegalNameException if the given prefix and uri make up
131 * an illegal namespace name.
132 */
133 public static Namespace getNamespace(String prefix, String uri) {
134 // Sanity checking
135 if ((prefix == null) || (prefix.trim().equals(""))) {
136 prefix = "";
137 }
138 if ((uri == null) || (uri.trim().equals(""))) {
139 uri = "";
140 }
141
142 // Return existing namespace if found. The preexisting namespaces
143 // should all be legal. In other words, an illegal namespace won't
144 // have been placed in this. Thus we can do this test before
145 // verifying the URI and prefix.
146 String lookup = new StringBuffer(64)
147 .append(prefix).append('&').append(uri).toString();
148 Namespace preexisting = (Namespace) namespaces.get(lookup);
149 if (preexisting != null) {
150 return preexisting;
151 }
152
153 // Ensure proper naming
154 String reason;
155 if ((reason = Verifier.checkNamespacePrefix(prefix)) != null) {
156 throw new IllegalNameException(prefix, "Namespace prefix", reason);
157 }
158 if ((reason = Verifier.checkNamespaceURI(uri)) != null) {
159 throw new IllegalNameException(uri, "Namespace URI", reason);
160 }
161
162 // Unless the "empty" Namespace (no prefix and no URI), require a URI
163 if ((!prefix.equals("")) && (uri.equals(""))) {
164 throw new IllegalNameException("", "namespace",
165 "Namespace URIs must be non-null and non-empty Strings");
166 }
167
168 // Handle XML namespace mislabels. If the user requested the correct
169 // namespace and prefix -- xml, http://www.w3.org/XML/1998/namespace
170 // -- then it was already returned from the preexisting namespaces.
171 // Thus any use of the xml prefix or the
172 // http://www.w3.org/XML/1998/namespace URI at this point must be
173 // incorrect.
174 if (prefix.equals("xml")) {
175 throw new IllegalNameException(prefix, "Namespace prefix",
176 "The xml prefix can only be bound to " +
177 "http://www.w3.org/XML/1998/namespace");
178 }
179 // The erratum to Namespaces in XML 1.0 that suggests this
180 // next check is controversial. Not everyone accepts it.
181 if (uri.equals("http://www.w3.org/XML/1998/namespace")) {
182 throw new IllegalNameException(uri, "Namespace URI",
183 "The http://www.w3.org/XML/1998/namespace must be bound to " +
184 "the xml prefix.");
185 }
186
187 // Finally, store and return
188 Namespace ns = new Namespace(prefix, uri);
189 namespaces.put(lookup, ns);
190 return ns;
191 }
192
193 /**
194 * This will retrieve (if in existence) or create (if not) a
195 * <code>Namespace</code> for the supplied URI, and make it usable
196 * as a default namespace, as no prefix is supplied.
197 *
198 * @param uri <code>String</code> URI of new <code>Namespace</code>.
199 * @return <code>Namespace</code> - ready to use namespace.
200 */
201 public static Namespace getNamespace(String uri) {
202 return getNamespace("", uri);
203 }
204
205 /**
206 * This constructor handles creation of a <code>Namespace</code> object
207 * with a prefix and URI; it is intentionally left <code>private</code>
208 * so that it cannot be invoked by external programs/code.
209 *
210 * @param prefix <code>String</code> prefix to map to this namespace.
211 * @param uri <code>String</code> URI for namespace.
212 */
213 private Namespace(String prefix, String uri) {
214 this.prefix = prefix;
215 this.uri = uri;
216 }
217
218 /**
219 * This returns the prefix mapped to this <code>Namespace</code>.
220 *
221 * @return <code>String</code> - prefix for this <code>Namespace</code>.
222 */
223 public String getPrefix() {
224 return prefix;
225 }
226
227 /**
228 * This returns the namespace URI for this <code>Namespace</code>.
229 *
230 * @return <code>String</code> - URI for this <code>Namespace</code>.
231 */
232 public String getURI() {
233 return uri;
234 }
235
236 /**
237 * This tests for equality - Two <code>Namespaces</code>
238 * are equal if and only if their URIs are byte-for-byte equals.
239 *
240 * @param ob <code>Object</code> to compare to this <code>Namespace</code>.
241 * @return <code>boolean</code> - whether the supplied object is equal to
242 * this <code>Namespace</code>.
243 */
244 public boolean equals(Object ob) {
245 if (this == ob) {
246 return true;
247 }
248 if (ob instanceof Namespace) { // instanceof returns false if null
249 return uri.equals(((Namespace)ob).uri);
250 }
251 return false;
252 }
253
254 /**
255 * This returns a <code>String</code> representation of this
256 * <code>Namespace</code>, suitable for use in debugging.
257 *
258 * @return <code>String</code> - information about this instance.
259 */
260 public String toString() {
261 return "[Namespace: prefix \"" + prefix + "\" is mapped to URI \"" +
262 uri + "\"]";
263 }
264
265 /**
266 * This returns a probably unique hash code for the <code>Namespace</code>.
267 * If two namespaces have the same URI, they are equal and have the same
268 * hash code, even if they have different prefixes.
269 *
270 * @return <code>int</code> - hash code for this <code>Namespace</code>.
271 */
272 public int hashCode() {
273 return uri.hashCode();
274 }
275 }