javax.imageio.spi
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.

inputClass

protected Class inputClass

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

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.

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.

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:

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

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:

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

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.

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.