Class IIORegistry
- java.lang.Object
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- javax.imageio.spi.ServiceRegistry
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- javax.imageio.spi.IIORegistry
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public final class IIORegistry extends ServiceRegistry
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 ofImageReader,ImageWriter,ImageTranscoder,ImageInputStream, andImageOutputStream.Service providers found on the system classpath (typically the
lib/extdirectory in the Java installation directory) are automatically loaded as soon as this class is instantiated.When the
registerApplicationClasspathSpismethod 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, aservicessubdirectory is placed within theMETA-INFdirectory 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 namedcom.mycompany.imageio.MyFormatReaderSpiwhich implements theImageReaderSpiinterface, 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
ServiceRegistryclass. 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.
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Nested Class Summary
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Nested classes/interfaces inherited from class javax.imageio.spi.ServiceRegistry
ServiceRegistry.Filter
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method and Description static IIORegistrygetDefaultInstance()Returns the defaultIIORegistryinstance used by the Image I/O API.voidregisterApplicationClasspathSpis()Registers all available service providers found on the application class path, using the defaultClassLoader.-
Methods inherited from class javax.imageio.spi.ServiceRegistry
contains, deregisterAll, deregisterAll, deregisterServiceProvider, deregisterServiceProvider, finalize, getCategories, getServiceProviderByClass, getServiceProviders, getServiceProviders, lookupProviders, lookupProviders, registerServiceProvider, registerServiceProvider, registerServiceProviders, setOrdering, unsetOrdering
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Method Detail
getDefaultInstance
public static IIORegistry getDefaultInstance()
Returns the defaultIIORegistryinstance used by the Image I/O API. This instance should be used for all registry functions.Each
ThreadGroupwill receive its own instance; this allows differentApplets in the same browser (for example) to each have their own registry.- Returns:
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the default registry for the current
ThreadGroup.
registerApplicationClasspathSpis
public void registerApplicationClasspathSpis()
Registers all available service providers found on the application class path, using the defaultClassLoader. This method is typically invoked by theImageIO.scanForPluginsmethod.
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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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