Package com.google.common.io

Class FileBackedOutputStream

java.lang.Object

java.io.OutputStream

com.google.common.io.FileBackedOutputStream

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable

public final class FileBackedOutputStream
extends java.io.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

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	FileBackedOutputStream.MemoryOutput	ByteArrayOutputStream that exposes its internals.

Field Summary

Fields

Modifier and Type	Field	Description
private java.io.File	file
private int	fileThreshold
private FileBackedOutputStream.MemoryOutput	memory
private java.io.OutputStream	out
private java.io.File	parentDirectory
private boolean	resetOnFinalize
private ByteSource	source

Constructor Summary

Constructors

Modifier	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.
private	FileBackedOutputStream(int fileThreshold, boolean resetOnFinalize, java.io.File parentDirectory)

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()
void	flush()
(package private) java.io.File	getFile()	Returns the file holding the data (possibly null).
private java.io.InputStream	openInputStream()
void	reset()	Calls close() if not already closed, and then resets this object back to its initial state, for reuse.
private void	update(int len)	Checks if writing len bytes would go over threshold, and switches to file buffering if so.
void	write(byte[] b)
void	write(byte[] b, int off, int len)
void	write(int b)

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

Field Detail

fileThreshold

private final int fileThreshold

resetOnFinalize

private final boolean resetOnFinalize

source

private final ByteSource source

parentDirectory

private final java.io.File parentDirectory

out

private java.io.OutputStream out

memory

private FileBackedOutputStream.MemoryOutput memory

file

private java.io.File file

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.

FileBackedOutputStream

private FileBackedOutputStream(int fileThreshold,
                               boolean resetOnFinalize,
                               java.io.File parentDirectory)

Method Detail

getFile

java.io.File getFile()

Returns the file holding the data (possibly null).

asByteSource

public ByteSource asByteSource()

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

Since:

15.0

openInputStream

private java.io.InputStream openInputStream()
                                     throws java.io.IOException

Throws:

java.io.IOException

reset

public void reset()
           throws java.io.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:

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

write

public void write(int b)
           throws java.io.IOException

Specified by:

write in class java.io.OutputStream

Throws:

java.io.IOException

write

public void write(byte[] b)
           throws java.io.IOException

Overrides:

write in class java.io.OutputStream

Throws:

java.io.IOException

write

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

Overrides:

write in class java.io.OutputStream

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Overrides:

close in class java.io.OutputStream

Throws:

java.io.IOException

flush

public void flush()
           throws java.io.IOException

Specified by:

flush in interface java.io.Flushable

Overrides:

flush in class java.io.OutputStream

Throws:

java.io.IOException

update

private void update(int len)
             throws java.io.IOException

Checks if writing len bytes would go over threshold, and switches to file buffering if so.

Throws:

java.io.IOException