Package org.apache.sis.internal.storage.image

Class FormatFinder

java.lang.Object

org.apache.sis.internal.storage.image.FormatFinder

All Implemented Interfaces:

AutoCloseable

final class FormatFinder
extends Object
implements AutoCloseable

Helper class for finding the ImageReader or ImageWriter instance to use. This is a temporary object used only at WorldFileStore construction time. It also helps to choose which WorldFileStore subclass to instantiate.

Since:

1.2

Version:

1.3

Field Summary

Fields

Modifier and Type	Field	Description
(package private) final StorageConnector	connector	Information about the storage (URL, stream, etc).
(package private) final boolean	fileIsEmpty	true if the file is known to be empty, or false in case of doubt.
(package private) final boolean	isWritable	true if the storage seems to be writable.
(package private) Object	keepOpen	The connector object to keep open if we successfully created a WorldFileStore.
(package private) final boolean	openAsWriter	true if the storage should be open is write mode instead of read mode.
(package private) final WorldFileStoreProvider	provider	The factory that created this DataStore instance, or null if unspecified.
private ImageReader	reader	The image reader if specified or created by this FormatFinder, or null.
private boolean	readerLookupDone	Whether we already made an attempt to find the image reader or writer using ImageIO registry.
(package private) final Object	storage	The file, URL or stream where to read or write the image.
(package private) final String	suffix	The filename extension (may be an empty string), or null if unknown.
private ImageWriter	writer	The image writer if specified or created by this FormatFinder, or null.
private boolean	writerLookupDone	Whether we already made an attempt to find the image reader or writer using ImageIO registry.

Constructor Summary

Constructors

Constructor	Description
FormatFinder(WorldFileStoreProvider provider, StorageConnector connector)	Creates a new format finder.

Method Summary

Modifier and Type	Method	Description
final void	close()	Closes all unused resources.
(package private) final String[]	getFormatName()	Returns the name of the format.
(package private) final ImageReader	getOrCreateReader()	Returns the user-specified reader or searches for a reader that claim to be able to read the storage input.
(package private) final ImageWriter	getOrCreateWriter()	Returns the user-specified writer or searches for a writer for the file suffix.
private static IOException	unwrap(IIOException e)	Returns the cause of given exception if it exists, or the exception itself otherwise.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

provider

final WorldFileStoreProvider provider

The factory that created this DataStore instance, or null if unspecified.

connector

final StorageConnector connector

Information about the storage (URL, stream, etc).

keepOpen

Object keepOpen

The connector object to keep open if we successfully created a WorldFileStore. This is often the same object than storage but may be different if an ImageInputStream has been created from the storage object.

This value is null until successful instantiation of image reader or writer. A null value means to close everything, which is the desired behavior in case of failure.

storage

final Object storage

The file, URL or stream where to read or write the image. If the user-specified storage was an ImageReader or ImageWriter, then the value stored in this field is the input/output of the reader/writer.

reader

private ImageReader reader

The image reader if specified or created by this FormatFinder, or null.

writer

private ImageWriter writer

The image writer if specified or created by this FormatFinder, or null.

readerLookupDone

private boolean readerLookupDone

Whether we already made an attempt to find the image reader or writer using ImageIO registry.

writerLookupDone

private boolean writerLookupDone

Whether we already made an attempt to find the image reader or writer using ImageIO registry.

isWritable

final boolean isWritable

true if the storage seems to be writable.

openAsWriter

final boolean openAsWriter

true if the storage should be open is write mode instead of read mode. This is true if the file does not exist or the file is empty.

fileIsEmpty

final boolean fileIsEmpty

true if the file is known to be empty, or false in case of doubt.

suffix

final String suffix

The filename extension (may be an empty string), or null if unknown. It does not include the leading dot.

Constructor Details

FormatFinder

FormatFinder(WorldFileStoreProvider provider,
 StorageConnector connector)
      throws DataStoreException,
IOException

Creates a new format finder.

Parameters:

provider - the factory that created this DataStore instance, or null if unspecified.

connector - information about the storage (URL, stream, etc).

Throws:

DataStoreException

IOException

Method Details

getFormatName

final String[] getFormatName()
                      throws DataStoreException,
IOException

Returns the name of the format.

Returns:

name of the format, or null if unknown.

Throws:

DataStoreException

IOException

getOrCreateReader

final ImageReader getOrCreateReader()
                             throws DataStoreException,
IOException

Returns the user-specified reader or searches for a reader that claim to be able to read the storage input. This method tries first the readers associated to the file suffix. If no reader is found, then this method tries all other readers.

Returns:

the reader, or null if none could be found.

Throws:

DataStoreException

IOException

getOrCreateWriter

final ImageWriter getOrCreateWriter()
                             throws DataStoreException,
IOException

Returns the user-specified writer or searches for a writer for the file suffix.

Returns:

the writer, or null if none could be found.

Throws:

DataStoreException

IOException

unwrap

@Workaround(library="JDK",
            version="18")
private static IOException unwrap(IIOException e)

Returns the cause of given exception if it exists, or the exception itself otherwise. This method is invoked in the catch block of a try block invoking ImageIO.createImageInputStream(Object) or ImageIO.createImageOutputStream(Object).

Rational

As of Java 18, above-cited methods systematically catch all IOExceptions and wrap them in an IIOException with "Cannot create cache file!" error message. This is conform to Image I/O specification but misleading if the stream provider throws an IOException for another reason. Even when the failure is really caused by a problem with cache file, we want to propagate the original exception to user because its message may tell that there is no space left on device or no write permission.

See Also:

• StorageConnector.unwrap(IIOException)

close

public final void close()
                 throws DataStoreException

Closes all unused resources. Keep open only the find of objects needed by the image reader or writer. This method must be invoked after by WorldFileStore construction.

Specified by:

close in interface AutoCloseable

Throws:

DataStoreException