Class ImageInputStreamSpi

java.lang.Object

javax.imageio.spi.IIOServiceProvider

javax.imageio.spi.ImageInputStreamSpi

All Implemented Interfaces:

RegisterableService

public abstract class ImageInputStreamSpi
extends IIOServiceProvider

The service provider interface (SPI) for ImageInputStreams. For more information on service provider interfaces, see the class comment for the IIORegistry class.

This interface allows arbitrary objects to be "wrapped" by instances of ImageInputStream. For example, a particular ImageInputStreamSpi might allow a generic InputStream to be used as an input source; another might take input from a URL.

By treating the creation of ImageInputStreams as a pluggable service, it becomes possible to handle future input sources without changing the API. Also, high-performance implementations of ImageInputStream (for example, native implementations for a particular platform) can be installed and used transparently by applications.

See Also:

• IIORegistry
• ImageInputStream

Field Summary

Fields

Modifier and Type	Field	Description
protected Class<?>	inputClass	A Class object indicating the legal object type for use by the createInputStreamInstance method.

Fields declared in class IIOServiceProvider

vendorName, version

Modifier and Type	Field	Description
protected String	vendorName	A String to be returned from getVendorName, initially null.
protected String	version	A String to be returned from getVersion, initially null.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ImageInputStreamSpi()	Constructs a blank ImageInputStreamSpi.
	ImageInputStreamSpi(String vendorName, String version, Class<?> inputClass)	Constructs an ImageInputStreamSpi with a given set of values.

Method Summary

Modifier and Type	Method	Description
boolean	canUseCacheFile()	Returns true if the ImageInputStream implementation associated with this service provider can optionally make use of a cache file for improved performance and/or memory footrprint.
ImageInputStream	createInputStreamInstance(Object input)	Returns an instance of the ImageInputStream implementation associated with this service provider.
abstract ImageInputStream	createInputStreamInstance(Object input, boolean useCache, File cacheDir)	Returns an instance of the ImageInputStream implementation associated with this service provider.
Class<?>	getInputClass()	Returns a Class object representing the class or interface type that must be implemented by an input source in order to be "wrapped" in an ImageInputStream via the createInputStreamInstance method.
boolean	needsCacheFile()	Returns true if the ImageInputStream implementation associated with this service provider requires the use of a cache File.

Methods declared in class IIOServiceProvider

getDescription, getVendorName, getVersion, onDeregistration, onRegistration

Modifier and Type	Method	Description
abstract String	getDescription(Locale locale)	Returns a brief, human-readable description of this service provider and its associated implementation.
String	getVendorName()	Returns the name of the vendor responsible for creating this service provider and its associated implementation.
String	getVersion()	Returns a string describing the version number of this service provider and its associated implementation.
void	onDeregistration(ServiceRegistry registry, Class<?> category)	A callback that will be whenever the Spi class has been deregistered from a ServiceRegistry.
void	onRegistration(ServiceRegistry registry, Class<?> category)	A callback that will be called exactly once after the Spi class has been instantiated and registered in a ServiceRegistry.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Field Details

inputClass

protected Class<?> inputClass

A Class object indicating the legal object type for use by the createInputStreamInstance method.

Constructor Details

ImageInputStreamSpi

protected ImageInputStreamSpi()

Constructs a blank ImageInputStreamSpi. It is up to the subclass to initialize instance variables and/or override method implementations in order to provide working versions of all methods.

ImageInputStreamSpi

public ImageInputStreamSpi(String vendorName,
 String version,
 Class<?> inputClass)

Constructs an ImageInputStreamSpi with a given set of values.

Parameters:

vendorName - the vendor name.

version - a version identifier.

inputClass - a Class object indicating the legal object type for use by the createInputStreamInstance method.

Throws:

IllegalArgumentException - if vendorName is null.

IllegalArgumentException - if version is null.

Method Details

getInputClass

public Class<?> getInputClass()

Returns a Class object representing the class or interface type that must be implemented by an input source in order to be "wrapped" in an ImageInputStream via the createInputStreamInstance method.

Typical return values might include InputStream.class or URL.class, but any class may be used.

Returns:

a Class variable.

See Also:

• createInputStreamInstance(Object, boolean, File)

canUseCacheFile

public boolean canUseCacheFile()

Returns true if the ImageInputStream implementation associated with this service provider can optionally make use of a cache file for improved performance and/or memory footrprint. If false, the value of the useCache argument to createInputStreamInstance will be ignored.

The default implementation returns false.

Returns:

true if a cache file can be used by the input streams created by this service provider.

needsCacheFile

public boolean needsCacheFile()

Returns true if the ImageInputStream implementation associated with this service provider requires the use of a cache File. If true, the value of the useCache argument to createInputStreamInstance will be ignored.

The default implementation returns false.

Returns:

true if a cache file is needed by the input streams created by this service provider.

createInputStreamInstance

public abstract ImageInputStream createInputStreamInstance(Object input,
 boolean useCache,
 File cacheDir)
                                                    throws IOException

Returns an instance of the ImageInputStream implementation associated with this service provider. If the use of a cache file is optional, the useCache parameter will be consulted. Where a cache is required, or not applicable, the value of useCache will be ignored.

Parameters:

input - an object of the class type returned by getInputClass.

useCache - a boolean indicating whether a cache file should be used, in cases where it is optional.

cacheDir - a File indicating where the cache file should be created, or null to use the system directory.

Returns:

an ImageInputStream instance.

Throws:

IllegalArgumentException - if input is not an instance of the correct class or is null.

IllegalArgumentException - if a cache file is needed but cacheDir is non-null and is not a directory.

IOException - if a cache file is needed but cannot be created.

See Also:

• getInputClass()
• canUseCacheFile()
• needsCacheFile()

createInputStreamInstance

public ImageInputStream createInputStreamInstance(Object input)
                                           throws IOException

Returns an instance of the ImageInputStream implementation associated with this service provider. A cache file will be created in the system-dependent default temporary-file directory, if needed.

Parameters:

input - an object of the class type returned by getInputClass.

Returns:

an ImageInputStream instance.

Throws:

IllegalArgumentException - if input is not an instance of the correct class or is null.

IOException - if a cache file is needed but cannot be created.

See Also:

• getInputClass()