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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package javax.imageio.spi;
import java.io.File;
import java.io.IOException;
import javax.imageio.stream.ImageInputStream;
/**
* The service provider interface (SPI) for
* {@code ImageInputStream}s. For more information on service
* provider interfaces, see the class comment for the
* {@code IIORegistry} class.
*
* <p> This interface allows arbitrary objects to be "wrapped" by
* instances of {@code ImageInputStream}. For example,
* a particular {@code ImageInputStreamSpi} might allow
* a generic {@code InputStream} to be used as an input source;
* another might take input from a {@code URL}.
*
* <p> By treating the creation of {@code ImageInputStream}s as a
* pluggable service, it becomes possible to handle future input
* sources without changing the API. Also, high-performance
* implementations of {@code ImageInputStream} (for example,
* native implementations for a particular platform) can be installed
* and used transparently by applications.
*
* @see IIORegistry
* @see javax.imageio.stream.ImageInputStream
*
*/
public abstract class ImageInputStreamSpi extends IIOServiceProvider {
/**
* A {@code Class} object indicating the legal object type
* for use by the {@code createInputStreamInstance} method.
*/
protected Class<?> inputClass;
/**
* Constructs a blank {@code 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.
*/
protected ImageInputStreamSpi() {
}
/**
* Constructs an {@code ImageInputStreamSpi} with a given set
* of values.
*
* @param vendorName the vendor name.
* @param version a version identifier.
* @param inputClass a {@code Class} object indicating the
* legal object type for use by the
* {@code createInputStreamInstance} method.
*
* @exception IllegalArgumentException if {@code vendorName}
* is {@code null}.
* @exception IllegalArgumentException if {@code version}
* is {@code null}.
*/
public ImageInputStreamSpi(String vendorName,
String version,
Class<?> inputClass) {
super(vendorName, version);
this.inputClass = inputClass;
}
/**
* Returns a {@code Class} object representing the class or
* interface type that must be implemented by an input source in
* order to be "wrapped" in an {@code ImageInputStream} via
* the {@code createInputStreamInstance} method.
*
* <p> Typical return values might include
* {@code InputStream.class} or {@code URL.class}, but
* any class may be used.
*
* @return a {@code Class} variable.
*
* @see #createInputStreamInstance(Object, boolean, File)
*/
public Class<?> getInputClass() {
return inputClass;
}
/**
* Returns {@code true} if the {@code ImageInputStream}
* implementation associated with this service provider can
* optionally make use of a cache file for improved performance
* and/or memory footrprint. If {@code false}, the value of
* the {@code useCache} argument to
* {@code createInputStreamInstance} will be ignored.
*
* <p> The default implementation returns {@code false}.
*
* @return {@code true} if a cache file can be used by the
* input streams created by this service provider.
*/
public boolean canUseCacheFile() {
return false;
}
/**
* Returns {@code true} if the {@code ImageInputStream}
* implementation associated with this service provider requires
* the use of a cache {@code File}. If {@code true},
* the value of the {@code useCache} argument to
* {@code createInputStreamInstance} will be ignored.
*
* <p> The default implementation returns {@code false}.
*
* @return {@code true} if a cache file is needed by the
* input streams created by this service provider.
*/
public boolean needsCacheFile() {
return false;
}
/**
* Returns an instance of the {@code ImageInputStream}
* implementation associated with this service provider. If the
* use of a cache file is optional, the {@code useCache}
* parameter will be consulted. Where a cache is required, or
* not applicable, the value of {@code useCache} will be ignored.
*
* @param input an object of the class type returned by
* {@code getInputClass}.
* @param useCache a {@code boolean} indicating whether a
* cache file should be used, in cases where it is optional.
* @param cacheDir a {@code File} indicating where the
* cache file should be created, or {@code null} to use the
* system directory.
*
* @return an {@code ImageInputStream} instance.
*
* @exception IllegalArgumentException if {@code input} is
* not an instance of the correct class or is {@code null}.
* @exception IllegalArgumentException if a cache file is needed
* but {@code cacheDir} is non-{@code null} and is not a
* directory.
* @exception IOException if a cache file is needed but cannot be
* created.
*
* @see #getInputClass
* @see #canUseCacheFile
* @see #needsCacheFile
*/
public abstract ImageInputStream
createInputStreamInstance(Object input,
boolean useCache,
File cacheDir) throws IOException;
/**
* Returns an instance of the {@code ImageInputStream}
* implementation associated with this service provider. A cache
* file will be created in the system-dependent default
* temporary-file directory, if needed.
*
* @param input an object of the class type returned by
* {@code getInputClass}.
*
* @return an {@code ImageInputStream} instance.
*
* @exception IllegalArgumentException if {@code input} is
* not an instance of the correct class or is {@code null}.
* @exception IOException if a cache file is needed but cannot be
* created.
*
* @see #getInputClass()
*/
public ImageInputStream createInputStreamInstance(Object input)
throws IOException {
return createInputStreamInstance(input, true, null);
}
}