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()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
String	toString()	Returns a string representation of the object.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

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()