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javax.imageio.spi
public final class: IIORegistry [javadoc | source]

java.lang.Object
   javax.imageio.spi.ServiceRegistry
      javax.imageio.spi.IIORegistry

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 (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.

Method from javax.imageio.spi.IIORegistry Summary:
getDefaultInstance,   registerApplicationClasspathSpis

Methods from javax.imageio.spi.ServiceRegistry:
contains,   deregisterAll,   deregisterAll,   deregisterServiceProvider,   deregisterServiceProvider,   finalize,   getCategories,   getServiceProviderByClass,   getServiceProviders,   getServiceProviders,   lookupProviders,   lookupProviders,   registerServiceProvider,   registerServiceProvider,   registerServiceProviders,   setOrdering,   unsetOrdering

Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait

Method from javax.imageio.spi.IIORegistry Detail:
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; } 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.
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; } } } } } 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.