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## javax.imageio.spi
Class ImageOutputStreamSpi

    java.lang.Object
      |
      +--javax.imageio.spi.IIOServiceProvider
            |
            +--javax.imageio.spi.ImageOutputStreamSpi

All Implemented Interfaces:
  RegisterableService

public abstract class ImageOutputStreamSpi
extends IIOServiceProvider

The service provider interface (SPI) for `ImageOutputStream`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 `ImageOutputStream`. For example, a particular `ImageOutputStreamSpi` might allow a generic `OutputStream` to be used as a destination; another might output to a `File` or to a device such as a serial port.

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

See Also:
  `IIORegistry`, `ImageOutputStream`

Field Summary
`protected Class` | `outputClass` 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` | `ImageOutputStreamSpi()` Constructs a blank `ImageOutputStreamSpi`.
`` | `ImageOutputStreamSpi(String vendorName, String version, Class outputClass)` Constructs an `ImageOutputStreamSpi` with a given set of values.

Method Summary
`boolean` | `canUseCacheFile()` Returns `true` if the `ImageOutputStream` implementation associated with this service provider can optionally make use of a cache `File` for improved performance and/or memory footrprint.
`ImageOutputStream` | `createOutputStreamInstance(Object output)` Returns an instance of the `ImageOutputStream` implementation associated with this service provider.
`abstract ImageOutputStream` | `createOutputStreamInstance(Object output, boolean useCache, File cacheDir)` Returns an instance of the `ImageOutputStream` implementation associated with this service provider.
`Class` | `getOutputClass()` Returns a `Class` object representing the class or interface type that must be implemented by an output destination in order to be "wrapped" in an `ImageOutputStream` via the `createOutputStreamInstance` method.
`boolean` | `needsCacheFile()` Returns `true` if the `ImageOutputStream` 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

### outputClass

    protected Class outputClass

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

Constructor Detail

### ImageOutputStreamSpi

    protected ImageOutputStreamSpi()

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

### ImageOutputStreamSpi

    public ImageOutputStreamSpi(String vendorName,
                                String version,
                                Class outputClass)

  Constructs an `ImageOutputStreamSpi` with a given set of values.

Parameters:
  `vendorName` - the vendor name.
  `version` - a version identifier.
  `outputClass` - a `Class` object indicating the legal object type for use by the `createOutputStreamInstance` method.
Throws:
  `IllegalArgumentException` - if `vendorName` is `null`.
  `IllegalArgumentException` - if `version` is `null`.

Method Detail

### getOutputClass

    public Class getOutputClass()

  Returns a `Class` object representing the class or interface type that must be implemented by an output destination in order to be "wrapped" in an `ImageOutputStream` via the `createOutputStreamInstance` method.

  Typical return values might include `OutputStream.class` or `File.class`, but any class may be used.

  Returns:
    a `Class` variable.
  See Also:
    `createOutputStreamInstance(Object, boolean, File)`

### canUseCacheFile

    public boolean canUseCacheFile()

  Returns `true` if the `ImageOutputStream` 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 `cacheFile` argument to `createOutputStreamInstance` will be ignored.

  The default implementation returns `false`.

  Returns:
    `true` if a cache file can be used by the output streams created by this service provider.

### needsCacheFile

    public boolean needsCacheFile()

  Returns `true` if the `ImageOutputStream` implementation associated with this service provider requires the use of a cache `File`.

  The default implementation returns `false`.

  Returns:
    `true` if a cache file is needed by the output streams created by this service provider.

### createOutputStreamInstance

    public abstract ImageOutputStream createOutputStreamInstance(Object output,
                                                                 boolean useCache,
                                                                 File cacheDir)
                                                          throws IOException

  Returns an instance of the `ImageOutputStream` 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:
    `output` - an object of the class type returned by `getOutputClass`.
    `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 `ImageOutputStream` instance.
  Throws:
    `IllegalArgumentException` - if `output` 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:
    `getOutputClass()`

### createOutputStreamInstance

    public ImageOutputStream createOutputStreamInstance(Object output)
                                                 throws IOException

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

  Parameters:
    `output` - an object of the class type returned by `getOutputClass`.
  Returns:
    an `ImageOutputStream` instance.
  Throws:
    `IllegalArgumentException` - if `output` is not an instance of the correct class or is `null`.
    `IOException` - if a cache file is needed but cannot be created.
  See Also:
    `getOutputClass()`

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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.