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

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

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

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `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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