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## 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 `ImageInputStream`s. 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 `ImageInputStream`s 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
`protected Class` | `inputClass` A `Class` object indicating the legal object type for use by the `createInputStreamInstance` method.

Fields inherited from class javax.imageio.spi.IIOServiceProvider
`vendorName, version`

Constructor Summary
`protected` | `ImageInputStreamSpi()` Constructs a blank `ImageInputStreamSpi`.
`` | `ImageInputStreamSpi(String vendorName, String version, Class inputClass)` Constructs an `ImageInputStreamSpi` with a given set of values.

Method Summary
`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 inherited from class javax.imageio.spi.IIOServiceProvider
`getDescription, getVendorName, getVersion, onDeregistration, onRegistration`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### inputClass

    protected Class inputClass

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

Constructor Detail

### 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 Detail

### 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()`

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.