ImageReader,
* ImageWriter, ImageTranscoder,
* ImageInputStream, and ImageOutputStream.
*
* Service providers found on the system classpath (e.g.,
* the jre/lib/ext directory in Sun's implementation of
* JDK) are automatically loaded as soon as this class is
* instantiated.
*
*
When the registerApplicationClasspathSpis method
* is called, service provider instances declared in the
* meta-information section of JAR files on the application class path
* are loaded. To declare a service provider, a services
* subdirectory is placed within the META-INF directory
* that is present in every JAR file. This directory contains a file
* for each service provider interface that has one or more
* implementation classes present in the JAR file. For example, if
* the JAR file contained a class named
* com.mycompany.imageio.MyFormatReaderSpi which
* implements the ImageReaderSpi interface, the JAR file
* would contain a file named:
*
*
* META-INF/services/javax.imageio.spi.ImageReaderSpi ** * containing the line: * *
* com.mycompany.imageio.MyFormatReaderSpi ** *
The service provider classes are intended to be lightweight * and quick to load. Implementations of these interfaces * should avoid complex dependencies on other classes and on * native code. * *
It is also possible to manually add service providers not found
* automatically, as well as to remove those that are using the
* interfaces of the ServiceRegistry class. Thus
* the application may customize the contents of the registry as it
* sees fit.
*
*
For more details on declaring service providers, and the JAR
* format in general, see the
* JAR File Specification.
*
* @version 0.5
*/
public final class IIORegistry extends ServiceRegistry {
/**
* A Vector containing the valid IIO registry
* categories (superinterfaces) to be used in the constructor.
*/
private static final Vector initialCategories = new Vector(5);
static {
initialCategories.add(ImageReaderSpi.class);
initialCategories.add(ImageWriterSpi.class);
initialCategories.add(ImageTranscoderSpi.class);
initialCategories.add(ImageInputStreamSpi.class);
initialCategories.add(ImageOutputStreamSpi.class);
}
/**
* Set up the valid service provider categories and automatically
* register all available service providers.
*
*
The constructor is private in order to prevent creation of
* additional instances.
*/
private IIORegistry() {
super(initialCategories.iterator());
registerStandardSpis();
registerApplicationClasspathSpis();
}
/**
* Returns the default IIORegistry instance used by
* the Image I/O API. This instance should be used for all
* registry functions.
*
*
Each ThreadGroup will receive its own
* instance; this allows different Applets in the
* same browser (for example) to each have their own registry.
*
* @return the default registry for the current
* ThreadGroup.
*/
public static IIORegistry getDefaultInstance() {
AppContext context = AppContext.getAppContext();
IIORegistry registry =
(IIORegistry)context.get(IIORegistry.class);
if (registry == null) {
// Create an instance for this AppContext
registry = new IIORegistry();
context.put(IIORegistry.class, registry);
}
return registry;
}
private void registerStandardSpis() {
// Hardwire standard SPIs
registerServiceProvider(new GIFImageReaderSpi());
registerServiceProvider(new BMPImageReaderSpi());
registerServiceProvider(new BMPImageWriterSpi());
registerServiceProvider(new WBMPImageReaderSpi());
registerServiceProvider(new WBMPImageWriterSpi());
registerServiceProvider(new PNGImageReaderSpi());
registerServiceProvider(new PNGImageWriterSpi());
registerServiceProvider(new JPEGImageReaderSpi());
registerServiceProvider(new JPEGImageWriterSpi());
registerServiceProvider(new FileImageInputStreamSpi());
registerServiceProvider(new FileImageOutputStreamSpi());
registerServiceProvider(new InputStreamImageInputStreamSpi());
registerServiceProvider(new OutputStreamImageOutputStreamSpi());
registerServiceProvider(new RAFImageInputStreamSpi());
registerServiceProvider(new RAFImageOutputStreamSpi());
registerInstalledProviders();
}
/**
* Registers all available service providers found on the
* application class path, using the default
* ClassLoader. This method is typically invoked by
* the ImageIO.scanForPlugins method.
*
* @see javax.imageio.ImageIO#scanForPlugins
* @see ClassLoader#getResources
*/
public void registerApplicationClasspathSpis() {
// FIX: load only from application classpath
ClassLoader loader = Thread.currentThread().getContextClassLoader();
Iterator categories = getCategories();
while (categories.hasNext()) {
Class c = (Class)categories.next();
Iterator