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package javax.imageio.spi;

import java.security.PrivilegedAction;
import java.security.AccessController;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.Vector;
import com.sun.imageio.spi.FileImageInputStreamSpi;
import com.sun.imageio.spi.FileImageOutputStreamSpi;
import com.sun.imageio.spi.InputStreamImageInputStreamSpi;
import com.sun.imageio.spi.OutputStreamImageOutputStreamSpi;
import com.sun.imageio.spi.RAFImageInputStreamSpi;
import com.sun.imageio.spi.RAFImageOutputStreamSpi;
import com.sun.imageio.plugins.gif.GIFImageReaderSpi;
import com.sun.imageio.plugins.gif.GIFImageWriterSpi;
import com.sun.imageio.plugins.jpeg.JPEGImageReaderSpi;
import com.sun.imageio.plugins.jpeg.JPEGImageWriterSpi;
import com.sun.imageio.plugins.png.PNGImageReaderSpi;
import com.sun.imageio.plugins.png.PNGImageWriterSpi;
import com.sun.imageio.plugins.bmp.BMPImageReaderSpi;
import com.sun.imageio.plugins.bmp.BMPImageWriterSpi;
import com.sun.imageio.plugins.wbmp.WBMPImageReaderSpi;
import com.sun.imageio.plugins.wbmp.WBMPImageWriterSpi;
import sun.awt.AppContext;
import java.util.ServiceLoader;
import java.util.ServiceConfigurationError;

A registry for service provider instances. Service provider classes may be detected at run time by means of meta-information in the JAR files containing them. The intent is that it be relatively inexpensive to load and inspect all available service provider classes. These classes may them be used to locate and instantiate more heavyweight classes that will perform actual work, in this case instances of ImageReader, ImageWriter, ImageTranscoder, ImageInputStream, and ImageOutputStream.

Service providers found on the system classpath (typically the lib/ext directory in the Java installation directory) 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.

/** * A registry for service provider instances. Service provider * classes may be detected at run time by means of meta-information in * the JAR files containing them. The intent is that it be relatively * inexpensive to load and inspect all available service provider * classes. These classes may them be used to locate and instantiate * more heavyweight classes that will perform actual work, in this * case instances of <code>ImageReader</code>, * <code>ImageWriter</code>, <code>ImageTranscoder</code>, * <code>ImageInputStream</code>, and <code>ImageOutputStream</code>. * * <p> Service providers found on the system classpath (typically * the <code>lib/ext</code> directory in the Java * installation directory) are automatically loaded as soon as this class is * instantiated. * * <p> When the <code>registerApplicationClasspathSpis</code> 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 <code>services</code> * subdirectory is placed within the <code>META-INF</code> 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 * <code>com.mycompany.imageio.MyFormatReaderSpi</code> which * implements the <code>ImageReaderSpi</code> interface, the JAR file * would contain a file named: * * <pre> * META-INF/services/javax.imageio.spi.ImageReaderSpi * </pre> * * containing the line: * * <pre> * com.mycompany.imageio.MyFormatReaderSpi * </pre> * * <p> 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. * * <p> 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 <code>ServiceRegistry</code> class. Thus * the application may customize the contents of the registry as it * sees fit. * * <p> For more details on declaring service providers, and the JAR * format in general, see the <a * href="{@docRoot}/../technotes/guides/jar/jar.html"> * JAR File Specification</a>. * */
public final class IIORegistry extends ServiceRegistry {
A Vector containing the valid IIO registry categories (superinterfaces) to be used in the constructor.
/** * A <code>Vector</code> 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.

/** * Set up the valid service provider categories and automatically * register all available service providers. * * <p> 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.

Returns:the default registry for the current ThreadGroup.
/** * Returns the default <code>IIORegistry</code> instance used by * the Image I/O API. This instance should be used for all * registry functions. * * <p> Each <code>ThreadGroup</code> will receive its own * instance; this allows different <code>Applet</code>s in the * same browser (for example) to each have their own registry. * * @return the default registry for the current * <code>ThreadGroup</code>. */
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 GIFImageWriterSpi()); 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 Also:
/** * Registers all available service providers found on the * application class path, using the default * <code>ClassLoader</code>. This method is typically invoked by * the <code>ImageIO.scanForPlugins</code> 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<IIOServiceProvider> c = (Class)categories.next(); Iterator<IIOServiceProvider> riter = ServiceLoader.load(c, loader).iterator(); while (riter.hasNext()) { try { // Note that the next() call is required to be inside // the try/catch block; see 6342404. IIOServiceProvider r = riter.next(); registerServiceProvider(r); } catch (ServiceConfigurationError err) { if (System.getSecurityManager() != null) { // In the applet case, we will catch the error so // registration of other plugins can proceed err.printStackTrace(); } else { // In the application case, we will throw the // error to indicate app/system misconfiguration throw err; } } } } } private void registerInstalledProviders() { /* We need to load installed providers from the system classpath (typically the <code>lib/ext</code> directory in in the Java installation directory) in the privileged mode in order to be able read corresponding jar files even if file read capability is restricted (like the applet context case). */ PrivilegedAction doRegistration = new PrivilegedAction() { public Object run() { Iterator categories = getCategories(); while (categories.hasNext()) { Class<IIOServiceProvider> c = (Class)categories.next(); for (IIOServiceProvider p : ServiceLoader.loadInstalled(c)) { registerServiceProvider(p); } } return this; } }; AccessController.doPrivileged(doRegistration); } }