Module java.desktop
Package 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.

See Also:
IIORegistry, ImageInputStream

  • 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()