1 /*
2 * Copyright 1999-2007 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 package javax.imageio.spi;
27
28 import java.security.PrivilegedAction;
29 import java.security.AccessController;
30 import java.util.HashMap;
31 import java.util.Iterator;
32 import java.util.Map;
33 import java.util.NoSuchElementException;
34 import java.util.Set;
35 import java.util.Vector;
36 import com.sun.imageio.spi.FileImageInputStreamSpi;
37 import com.sun.imageio.spi.FileImageOutputStreamSpi;
38 import com.sun.imageio.spi.InputStreamImageInputStreamSpi;
39 import com.sun.imageio.spi.OutputStreamImageOutputStreamSpi;
40 import com.sun.imageio.spi.RAFImageInputStreamSpi;
41 import com.sun.imageio.spi.RAFImageOutputStreamSpi;
42 import com.sun.imageio.plugins.gif.GIFImageReaderSpi;
43 import com.sun.imageio.plugins.gif.GIFImageWriterSpi;
44 import com.sun.imageio.plugins.jpeg.JPEGImageReaderSpi;
45 import com.sun.imageio.plugins.jpeg.JPEGImageWriterSpi;
46 import com.sun.imageio.plugins.png.PNGImageReaderSpi;
47 import com.sun.imageio.plugins.png.PNGImageWriterSpi;
48 import com.sun.imageio.plugins.bmp.BMPImageReaderSpi;
49 import com.sun.imageio.plugins.bmp.BMPImageWriterSpi;
50 import com.sun.imageio.plugins.wbmp.WBMPImageReaderSpi;
51 import com.sun.imageio.plugins.wbmp.WBMPImageWriterSpi;
52 import sun.awt.AppContext;
53 import java.util.ServiceLoader;
54 import java.util.ServiceConfigurationError;
55
56 /**
57 * A registry for service provider instances. Service provider
58 * classes may be detected at run time by means of meta-information in
59 * the JAR files containing them. The intent is that it be relatively
60 * inexpensive to load and inspect all available service provider
61 * classes. These classes may them be used to locate and instantiate
62 * more heavyweight classes that will perform actual work, in this
63 * case instances of <code>ImageReader</code>,
64 * <code>ImageWriter</code>, <code>ImageTranscoder</code>,
65 * <code>ImageInputStream</code>, and <code>ImageOutputStream</code>.
66 *
67 * <p> Service providers found on the system classpath (<i>e.g.</i>,
68 * the <code>jre/lib/ext</code> directory in Sun's implementation of
69 * JDK) are automatically loaded as soon as this class is
70 * instantiated.
71 *
72 * <p> When the <code>registerApplicationClasspathSpis</code> method
73 * is called, service provider instances declared in the
74 * meta-information section of JAR files on the application class path
75 * are loaded. To declare a service provider, a <code>services</code>
76 * subdirectory is placed within the <code>META-INF</code> directory
77 * that is present in every JAR file. This directory contains a file
78 * for each service provider interface that has one or more
79 * implementation classes present in the JAR file. For example, if
80 * the JAR file contained a class named
81 * <code>com.mycompany.imageio.MyFormatReaderSpi</code> which
82 * implements the <code>ImageReaderSpi</code> interface, the JAR file
83 * would contain a file named:
84 *
85 * <pre>
86 * META-INF/services/javax.imageio.spi.ImageReaderSpi
87 * </pre>
88 *
89 * containing the line:
90 *
91 * <pre>
92 * com.mycompany.imageio.MyFormatReaderSpi
93 * </pre>
94 *
95 * <p> The service provider classes are intended to be lightweight
96 * and quick to load. Implementations of these interfaces
97 * should avoid complex dependencies on other classes and on
98 * native code.
99 *
100 * <p> It is also possible to manually add service providers not found
101 * automatically, as well as to remove those that are using the
102 * interfaces of the <code>ServiceRegistry</code> class. Thus
103 * the application may customize the contents of the registry as it
104 * sees fit.
105 *
106 * <p> For more details on declaring service providers, and the JAR
107 * format in general, see the <a
108 * href="{@docRoot}/../technotes/guides/jar/jar.html">
109 * JAR File Specification</a>.
110 *
111 */
112 public final class IIORegistry extends ServiceRegistry {
113
114 /**
115 * A <code>Vector</code> containing the valid IIO registry
116 * categories (superinterfaces) to be used in the constructor.
117 */
118 private static final Vector initialCategories = new Vector(5);
119
120 static {
121 initialCategories.add(ImageReaderSpi.class);
122 initialCategories.add(ImageWriterSpi.class);
123 initialCategories.add(ImageTranscoderSpi.class);
124 initialCategories.add(ImageInputStreamSpi.class);
125 initialCategories.add(ImageOutputStreamSpi.class);
126 }
127
128 /**
129 * Set up the valid service provider categories and automatically
130 * register all available service providers.
131 *
132 * <p> The constructor is private in order to prevent creation of
133 * additional instances.
134 */
135 private IIORegistry() {
136 super(initialCategories.iterator());
137 registerStandardSpis();
138 registerApplicationClasspathSpis();
139 }
140
141 /**
142 * Returns the default <code>IIORegistry</code> instance used by
143 * the Image I/O API. This instance should be used for all
144 * registry functions.
145 *
146 * <p> Each <code>ThreadGroup</code> will receive its own
147 * instance; this allows different <code>Applet</code>s in the
148 * same browser (for example) to each have their own registry.
149 *
150 * @return the default registry for the current
151 * <code>ThreadGroup</code>.
152 */
153 public static IIORegistry getDefaultInstance() {
154 AppContext context = AppContext.getAppContext();
155 IIORegistry registry =
156 (IIORegistry)context.get(IIORegistry.class);
157 if (registry == null) {
158 // Create an instance for this AppContext
159 registry = new IIORegistry();
160 context.put(IIORegistry.class, registry);
161 }
162 return registry;
163 }
164
165 private void registerStandardSpis() {
166 // Hardwire standard SPIs
167 registerServiceProvider(new GIFImageReaderSpi());
168 registerServiceProvider(new GIFImageWriterSpi());
169 registerServiceProvider(new BMPImageReaderSpi());
170 registerServiceProvider(new BMPImageWriterSpi());
171 registerServiceProvider(new WBMPImageReaderSpi());
172 registerServiceProvider(new WBMPImageWriterSpi());
173 registerServiceProvider(new PNGImageReaderSpi());
174 registerServiceProvider(new PNGImageWriterSpi());
175 registerServiceProvider(new JPEGImageReaderSpi());
176 registerServiceProvider(new JPEGImageWriterSpi());
177 registerServiceProvider(new FileImageInputStreamSpi());
178 registerServiceProvider(new FileImageOutputStreamSpi());
179 registerServiceProvider(new InputStreamImageInputStreamSpi());
180 registerServiceProvider(new OutputStreamImageOutputStreamSpi());
181 registerServiceProvider(new RAFImageInputStreamSpi());
182 registerServiceProvider(new RAFImageOutputStreamSpi());
183
184 registerInstalledProviders();
185 }
186
187 /**
188 * Registers all available service providers found on the
189 * application class path, using the default
190 * <code>ClassLoader</code>. This method is typically invoked by
191 * the <code>ImageIO.scanForPlugins</code> method.
192 *
193 * @see javax.imageio.ImageIO#scanForPlugins
194 * @see ClassLoader#getResources
195 */
196 public void registerApplicationClasspathSpis() {
197 // FIX: load only from application classpath
198
199 ClassLoader loader = Thread.currentThread().getContextClassLoader();
200
201 Iterator categories = getCategories();
202 while (categories.hasNext()) {
203 Class<IIOServiceProvider> c = (Class)categories.next();
204 Iterator<IIOServiceProvider> riter =
205 ServiceLoader.load(c, loader).iterator();
206 while (riter.hasNext()) {
207 try {
208 // Note that the next() call is required to be inside
209 // the try/catch block; see 6342404.
210 IIOServiceProvider r = riter.next();
211 registerServiceProvider(r);
212 } catch (ServiceConfigurationError err) {
213 if (System.getSecurityManager() != null) {
214 // In the applet case, we will catch the error so
215 // registration of other plugins can proceed
216 err.printStackTrace();
217 } else {
218 // In the application case, we will throw the
219 // error to indicate app/system misconfiguration
220 throw err;
221 }
222 }
223 }
224 }
225 }
226
227 private void registerInstalledProviders() {
228 /*
229 We need load installed providers from lib/ext
230 directory in the privileged mode in order to
231 be able read corresponding jar files even if
232 file read capability is restricted (like the
233 applet context case).
234 */
235 PrivilegedAction doRegistration =
236 new PrivilegedAction() {
237 public Object run() {
238 Iterator categories = getCategories();
239 while (categories.hasNext()) {
240 Class<IIOServiceProvider> c = (Class)categories.next();
241 for (IIOServiceProvider p : ServiceLoader.loadInstalled(c)) {
242 registerServiceProvider(p);
243 }
244 }
245 return this;
246 }
247 };
248
249 AccessController.doPrivileged(doRegistration);
250 }
251 }
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