org.entityfs.util.io
Class GZipWritableFile

java.lang.Object
  org.entityfs.util.io.GZipWritableFile

All Implemented Interfaces:

Lockable, WriteLockable, WritableFile

public class GZipWritableFile
extends Object
implements WritableFile

This is a WritableFile that transparently compresses the data written to a file using gzip compression. The gzip output stream is opened on a buffered output stream whose buffer size can be set.

This file cannot be appended to. The openForAppend methods throw an UnsupportedOperationException.

Since:

1.1

Author:

Karl Gustafsson

See Also:

GZipReadableFile

Constructor Summary

GZipWritableFile(WritableFile adapted)
Create a new adapter using the default gzip buffer size and compression level (6).

GZipWritableFile(WritableFile adapted, int compressionLevel)
Create a new adapter using a custom compression level and the default buffer sizes.

GZipWritableFile(WritableFile adapted, int compressionLevel, int bufSize, int outBufSize)
Create a new adapter using the supplied gzip buffer size.

Method Summary

EntityLock	getWriteLock() Get the write lock without locking it.
boolean	isWriteLockedByCurrentThread() Does the calling thread hold a write lock for the lockable object (this)?
EntityLock	lockForWriting() Lock the object for writing and return the lock.
WritableByteChannel	openChannelForAppend() This method always throws an UnsupportedOperationException.
WritableByteChannel	openChannelForWrite() Open a WritableByteChannel for writing on the file.
OutputStream	openForAppend() This method always throws an UnsupportedOperationException.
OutputStream	openForWrite() Opens the file for writing.

Methods inherited from class java.lang.Object

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

Constructor Detail

GZipWritableFile

public GZipWritableFile(WritableFile adapted)

Create a new adapter using the default gzip buffer size and compression level (6).

Parameters:

adapted - The writable file to adapt.

GZipWritableFile

public GZipWritableFile(WritableFile adapted,
                        int compressionLevel)
                 throws IllegalArgumentException

Create a new adapter using a custom compression level and the default buffer sizes.

Parameters:

adapted - The writable file to adapt.

compressionLevel - The level of compression to use for the file. The compression is in the range from 1 (fastest, worst compression) to 9 (slowest, best compression).

Throws:

IllegalArgumentException - If the compression level is not in the permitted range.

GZipWritableFile

public GZipWritableFile(WritableFile adapted,
                        int compressionLevel,
                        int bufSize,
                        int outBufSize)
                 throws IllegalArgumentException

Create a new adapter using the supplied gzip buffer size.

Parameters:

adapted - The writable file to adapt.

compressionLevel - The level of compression to use for the file. The compression is in the range from 1 (fastest, worst compression) to 9 (slowest, best compression).

bufSize - The size of the gzip compression buffer.

outBufSize - The size of the buffered output stream's buffer.

Throws:

IllegalArgumentException - If any of the buffer sizes are less than or equal to 0 or if the compression level is not in the permitted range.

Method Detail

openChannelForAppend

public WritableByteChannel openChannelForAppend()
                                         throws UnsupportedOperationException

This method always throws an UnsupportedOperationException.

Specified by:

openChannelForAppend in interface WritableFile

Returns:

An open WritableByteChannel. The channel must be closed by the caller. The returned channel may be a GatheringByteChannel, but that is not required.

Throws:

UnsupportedOperationException - Always.

openChannelForWrite

public WritableByteChannel openChannelForWrite()
                                        throws WriteLockRequiredException,
                                               AccessDeniedException,
                                               ReadOnlyException

Description copied from interface: WritableFile

Open a WritableByteChannel for writing on the file. The semantics of this method is the same as for WritableFile.openForWrite().

Specified by:

openChannelForWrite in interface WritableFile

Returns:

An open WritableByteChannel. The channel must be closed by the caller. The returned channel may be a GatheringByteChannel, but that is not required.

Throws:

WriteLockRequiredException - If the client does not have a write lock for the file.

AccessDeniedException - If the client does not have write access to the file.

ReadOnlyException - If the file system is read-only.

See Also:

WritableFile.openForWrite(), WritableFile.openChannelForAppend()

openForAppend

public OutputStream openForAppend()
                           throws UnsupportedOperationException

This method always throws an UnsupportedOperationException.

Specified by:

openForAppend in interface WritableFile

Returns:

An OutputStream to write to. The stream must be closed by the caller.

Throws:

UnsupportedOperationException - Always.

See Also:

WritableFile.openForWrite(), WritableFile.openChannelForAppend()

openForWrite

public OutputStream openForWrite()
                          throws WriteLockRequiredException,
                                 AccessDeniedException,
                                 ReadOnlyException

Description copied from interface: WritableFile

Opens the file for writing. This deletes all previous contents of the file. Use WritableFile.openForAppend() to append to the file.

The caller is responsible for closing the stream.

When two output streams, one writing and one appending are open on the same file, the stream opened for write will ignore the contents written by the other stream and the content written by the other stream will be overwritten. When two or more appending streams are opened on a file, a stream will not overwrite the content written by the other streams.

Although a write lock on the file is required for the execution thread opening the stream, the stream itself is not protected from access by other threads. It can be protected by wrapping it in a LockAwareOutputStream.

Specified by:

openForWrite in interface WritableFile

Returns:

An OutputStream to write to. The stream must be closed by the caller.

Throws:

WriteLockRequiredException - If the client does not have a write lock for the file.

AccessDeniedException - If the client does not have write access to the file.

ReadOnlyException - If the file system is read-only.

See Also:

WritableFile.openForAppend(), WritableFile.openChannelForWrite()

getWriteLock

public EntityLock getWriteLock()

Description copied from interface: WriteLockable

Get the write lock without locking it.

This method always returns a lock, even if the object's file system is not locking or if the object is read only.

Specified by:

getWriteLock in interface WriteLockable

Returns:

The lockable's write lock. This might be unlocked or locked by someone else.

isWriteLockedByCurrentThread

public boolean isWriteLockedByCurrentThread()

Description copied from interface: WriteLockable

Does the calling thread hold a write lock for the lockable object (this)?

Specified by:

isWriteLockedByCurrentThread in interface WriteLockable

Returns:

true if the lockable object is write locked by the current thread.

lockForWriting

public EntityLock lockForWriting()
                          throws LockTimeoutException

Description copied from interface: WriteLockable

Lock the object for writing and return the lock. How the lock is acquired is determined by the EntityLockAdapterFactory and LockAcquiringStrategy used. If this is called on an object that is somehow connected to an Entity object, that entity's file systems' lock adapter factory and lock acquiring strategy is used. A write lock can be downgraded to a read lock (by calling ReadLockable.lockForReading() and then releasing the write lock).

An entity in a locking read only file system may still be locked for writing.

For more discussions on locks and locking, see Entity and FileSystem.

This method always returns a lock, even if the file system is not locking.

Specified by:

lockForWriting in interface WriteLockable

Returns:

A locked write lock.

Throws:

LockTimeoutException - If the lock acquiring timed out. (It is up to the LockAcquiringStrategy to decide if lock acquiring can time out.)