net.hasor.cobble.io.output

类 DeferredFileOutputStream

java.lang.Object

java.io.OutputStream

net.hasor.cobble.io.output.ThresholdingOutputStream

net.hasor.cobble.io.output.DeferredFileOutputStream

所有已实现的接口:

Closeable, Flushable, AutoCloseable

public class DeferredFileOutputStream
extends ThresholdingOutputStream

An output stream which will retain data in memory until a specified threshold is reached, and only then commit it to disk. If the stream is closed before the threshold is reached, the data will not be written to disk at all.

This class originated in FileUpload processing. In this use case, you do not know in advance the size of the file being uploaded. If the file is small you want to store it in memory (for speed), but if the file is large you want to store it to file (to avoid memory issues). reduction based on Apache Commons IO, org.apache.commons.io.output.DeferredFileOutputStream

版本:

$Id: DeferredFileOutputStream.java 1307462 2012-03-30 15:13:11Z ggregory $

作者:

赵永春 (zyc@hasor.net)

构造器概要

构造器

构造器和说明
DeferredFileOutputStream(int threshold, File outputFile) Constructs an instance of this class which will trigger an event at the specified threshold, and save data to a file beyond that point.
DeferredFileOutputStream(int threshold, String prefix, String suffix, File directory) Constructs an instance of this class which will trigger an event at the specified threshold, and save data to a temporary file beyond that point.

方法概要

限定符和类型	方法和说明
void	close() Closes underlying output stream, and mark this as closed
byte[]	getData() Returns the data for this output stream as an array of bytes, assuming that the data has been retained in memory.
File	getFile() Returns either the output file specified in the constructor or the temporary file created or null.
protected OutputStream	getStream() Returns the current output stream.
boolean	isInMemory() Determines whether or not the data for this output stream has been retained in memory.
protected void	thresholdReached() Switches the underlying output stream from a memory based stream to one that is backed by disk.
void	writeTo(OutputStream out) Writes the data from this output stream to the specified output stream, after it has been closed.

从类继承的方法 net.hasor.cobble.io.output.ThresholdingOutputStream

checkThreshold, flush, getByteCount, getThreshold, isThresholdExceeded, resetByteCount, write, write, write

从类继承的方法 java.lang.Object

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

构造器详细资料

DeferredFileOutputStream

public DeferredFileOutputStream(int threshold,
                                File outputFile)

Constructs an instance of this class which will trigger an event at the specified threshold, and save data to a file beyond that point.

参数:

threshold - The number of bytes at which to trigger an event.

outputFile - The file to which data is saved beyond the threshold.

DeferredFileOutputStream

public DeferredFileOutputStream(int threshold,
                                String prefix,
                                String suffix,
                                File directory)

Constructs an instance of this class which will trigger an event at the specified threshold, and save data to a temporary file beyond that point.

参数:

threshold - The number of bytes at which to trigger an event.

prefix - Prefix to use for the temporary file.

suffix - Suffix to use for the temporary file.

directory - Temporary file directory.

从以下版本开始:

1.4

方法详细资料

getStream

protected OutputStream getStream()
                          throws IOException

Returns the current output stream. This may be memory based or disk based, depending on the current state with respect to the threshold.

指定者:

getStream 在类中 ThresholdingOutputStream

返回:

The underlying output stream.

抛出:

IOException - if an error occurs.

thresholdReached

protected void thresholdReached()
                         throws IOException

Switches the underlying output stream from a memory based stream to one that is backed by disk. This is the point at which we realise that too much data is being written to keep in memory, so we elect to switch to disk-based storage.

指定者:

thresholdReached 在类中 ThresholdingOutputStream

抛出:

IOException - if an error occurs.

isInMemory

public boolean isInMemory()

Determines whether or not the data for this output stream has been retained in memory.

返回:

true if the data is available in memory; false otherwise.

getData

public byte[] getData()

Returns the data for this output stream as an array of bytes, assuming that the data has been retained in memory. If the data was written to disk, this method returns null.

返回:

The data for this output stream, or null if no such data is available.

getFile

public File getFile()

Returns either the output file specified in the constructor or the temporary file created or null.

If the constructor specifying the file is used then it returns that same output file, even when threshold has not been reached.

If constructor specifying a temporary file prefix/suffix is used then the temporary file created once the threshold is reached is returned If the threshold was not reached then null is returned.

返回:

The file for this output stream, or null if no such file exists.

close

public void close()
           throws IOException

Closes underlying output stream, and mark this as closed

指定者:

close 在接口中 Closeable

指定者:

close 在接口中 AutoCloseable

覆盖:

close 在类中 ThresholdingOutputStream

抛出:

IOException - if an error occurs.

writeTo

public void writeTo(OutputStream out)
             throws IOException

Writes the data from this output stream to the specified output stream, after it has been closed.

参数:

out - output stream to write to.

抛出:

IOException - if this stream is not yet closed or an error occurs.