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

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `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

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `ImageOutputStreamSpi()` Constructs a blank `ImageOutputStreamSpi`.
    `` | `ImageOutputStreamSpi(String vendorName, String version, Class<?> outputClass)` Constructs an `ImageOutputStreamSpi` with a given set of values.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `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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