Package com.google.common.io

Class FileBackedOutputStream

java.lang.Object

java.io.OutputStream

com.google.common.io.FileBackedOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

@Beta
@GwtIncompatible
public final class FileBackedOutputStream
extends OutputStream

An OutputStream that starts buffering to a byte array, but switches to file buffering once the data reaches a configurable size.

Temporary files created by this stream may live in the local filesystem until either:

• reset() is called (removing the data in this stream and deleting the file), or...
• this stream (or, more precisely, its asByteSource() view) is finalized during garbage collection, AND this stream was not constructed with the 1-arg constructor or the 2-arg constructor passing false in the second parameter.

This class is thread-safe.

Since:

1.0

Author:

Chris Nokleberg

Constructor Summary

Constructors

Constructor	Description
FileBackedOutputStream(int fileThreshold)	Creates a new instance that uses the given file threshold, and does not reset the data when the ByteSource returned by asByteSource() is finalized.
FileBackedOutputStream(int fileThreshold, boolean resetOnFinalize)	Creates a new instance that uses the given file threshold, and optionally resets the data when the ByteSource returned by asByteSource() is finalized.

Method Summary

Modifier and Type	Method	Description
ByteSource	asByteSource()	Returns a readable ByteSource view of the data that has been written to this stream.
void	close()	Closes this output stream and releases any system resources associated with this stream.
void	flush()	Flushes this output stream and forces any buffered output bytes to be written out.
void	reset()	Calls close() if not already closed, and then resets this object back to its initial state, for reuse.
void	write(byte[] b)	Writes b.length bytes from the specified byte array to this output stream.
void	write(byte[] b, int off, int len)	Writes len bytes from the specified byte array starting at offset off to this output stream.
void	write(int b)	Writes the specified byte to this output stream.

Methods inherited from class java.io.OutputStream

nullOutputStream

Methods inherited from class java.lang.Object

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

Constructor Detail

FileBackedOutputStream

public FileBackedOutputStream(int fileThreshold)

Creates a new instance that uses the given file threshold, and does not reset the data when the ByteSource returned by asByteSource() is finalized.

Parameters:

fileThreshold - the number of bytes before the stream should switch to buffering to a file

FileBackedOutputStream

public FileBackedOutputStream(int fileThreshold,
                              boolean resetOnFinalize)

Creates a new instance that uses the given file threshold, and optionally resets the data when the ByteSource returned by asByteSource() is finalized.

Parameters:

fileThreshold - the number of bytes before the stream should switch to buffering to a file

resetOnFinalize - if true, the reset() method will be called when the ByteSource returned by asByteSource() is finalized.

Method Detail

asByteSource

public ByteSource asByteSource()

Returns a readable ByteSource view of the data that has been written to this stream.

Since:

15.0

reset

public void reset()
           throws IOException

Calls close() if not already closed, and then resets this object back to its initial state, for reuse. If data was buffered to a file, it will be deleted.

Throws:

IOException - if an I/O error occurred while deleting the file buffer

write

public void write(int b)
           throws IOException

Description copied from class: java.io.OutputStream

Writes the specified byte to this output stream. The general contract for write is that one byte is written to the output stream. The byte to be written is the eight low-order bits of the argument b. The 24 high-order bits of b are ignored.

Subclasses of OutputStream must provide an implementation for this method.

Specified by:

write in class OutputStream

Parameters:

b - the byte.

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.

write

public void write(byte[] b)
           throws IOException

Description copied from class: java.io.OutputStream

Writes b.length bytes from the specified byte array to this output stream. The general contract for write(b) is that it should have exactly the same effect as the call write(b, 0, b.length).

Overrides:

write in class OutputStream

Parameters:

b - the data.

Throws:

IOException - if an I/O error occurs.

See Also:

OutputStream.write(byte[], int, int)

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException

Description copied from class: java.io.OutputStream

Writes len bytes from the specified byte array starting at offset off to this output stream. The general contract for write(b, off, len) is that some of the bytes in the array b are written to the output stream in order; element b[off] is the first byte written and b[off+len-1] is the last byte written by this operation.

The write method of OutputStream calls the write method of one argument on each of the bytes to be written out. Subclasses are encouraged to override this method and provide a more efficient implementation.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

Overrides:

write in class OutputStream

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

IOException - if an I/O error occurs. In particular, an IOException is thrown if the output stream is closed.

close

public void close()
           throws IOException

Description copied from class: java.io.OutputStream

Closes this output stream and releases any system resources associated with this stream. The general contract of close is that it closes the output stream. A closed stream cannot perform output operations and cannot be reopened.

The close method of OutputStream does nothing.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class OutputStream

Throws:

IOException - if an I/O error occurs.

flush

public void flush()
           throws IOException

Description copied from class: java.io.OutputStream

Flushes this output stream and forces any buffered output bytes to be written out. The general contract of flush is that calling it is an indication that, if any bytes previously written have been buffered by the implementation of the output stream, such bytes should immediately be written to their intended destination.

If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written to the stream are passed to the operating system for writing; it does not guarantee that they are actually written to a physical device such as a disk drive.

The flush method of OutputStream does nothing.

Specified by:

flush in interface Flushable

Overrides:

flush in class OutputStream

Throws:

IOException - if an I/O error occurs.