Package org.apache.commons.io.output
Class DeferredFileOutputStream
- java.lang.Object
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- java.io.OutputStream
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- org.apache.commons.io.output.ThresholdingOutputStream
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- org.apache.commons.io.output.DeferredFileOutputStream
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- All Implemented Interfaces:
java.io.Closeable
,java.io.Flushable
,java.lang.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).
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Field Summary
Fields Modifier and Type Field Description private boolean
closed
True when close() has been called successfully.private java.io.OutputStream
currentOutputStream
The output stream to which data will be written at any given time.private java.io.File
directory
The directory to use for temporary files.private ByteArrayOutputStream
memoryOutputStream
The output stream to which data will be written prior to the threshold being reached.private java.io.File
outputFile
The file to which output will be directed if the threshold is exceeded.private java.lang.String
prefix
The temporary file prefix.private java.lang.String
suffix
The temporary file suffix.
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Constructor Summary
Constructors Modifier Constructor Description DeferredFileOutputStream(int threshold, int initialBufferSize, java.io.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, int initialBufferSize, java.lang.String prefix, java.lang.String suffix, java.io.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.DeferredFileOutputStream(int threshold, java.io.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.private
DeferredFileOutputStream(int threshold, java.io.File outputFile, java.lang.String prefix, java.lang.String suffix, java.io.File directory, int initialBufferSize)
Constructs an instance of this class which will trigger an event at the specified threshold, and save data either to a file beyond that point.DeferredFileOutputStream(int threshold, java.lang.String prefix, java.lang.String suffix, java.io.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.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Closes underlying output stream, and mark this as closedbyte[]
getData()
Returns the data for this output stream as an array of bytes, assuming that the data has been retained in memory.java.io.File
getFile()
Returns either the output file specified in the constructor or the temporary file created or null.protected java.io.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(java.io.OutputStream out)
Writes the data from this output stream to the specified output stream, after it has been closed.-
Methods inherited from class org.apache.commons.io.output.ThresholdingOutputStream
checkThreshold, flush, getByteCount, getThreshold, isThresholdExceeded, resetByteCount, setByteCount, write, write, write
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Field Detail
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memoryOutputStream
private ByteArrayOutputStream memoryOutputStream
The output stream to which data will be written prior to the threshold being reached.
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currentOutputStream
private java.io.OutputStream currentOutputStream
The output stream to which data will be written at any given time. This will always be one ofmemoryOutputStream
ordiskOutputStream
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outputFile
private java.io.File outputFile
The file to which output will be directed if the threshold is exceeded.
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prefix
private final java.lang.String prefix
The temporary file prefix.
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suffix
private final java.lang.String suffix
The temporary file suffix.
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directory
private final java.io.File directory
The directory to use for temporary files.
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closed
private boolean closed
True when close() has been called successfully.
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Constructor Detail
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DeferredFileOutputStream
public DeferredFileOutputStream(int threshold, java.io.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. The initial buffer size will default to 1024 bytes which is ByteArrayOutputStream's default buffer size.- Parameters:
threshold
- The number of bytes at which to trigger an event.outputFile
- The file to which data is saved beyond the threshold.
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DeferredFileOutputStream
public DeferredFileOutputStream(int threshold, int initialBufferSize, java.io.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.- Parameters:
threshold
- The number of bytes at which to trigger an event.initialBufferSize
- The initial size of the in memory buffer.outputFile
- The file to which data is saved beyond the threshold.- Since:
- 2.5
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DeferredFileOutputStream
public DeferredFileOutputStream(int threshold, java.lang.String prefix, java.lang.String suffix, java.io.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. The initial buffer size will default to 32 bytes which is ByteArrayOutputStream's default buffer size.- Parameters:
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.- Since:
- 1.4
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DeferredFileOutputStream
public DeferredFileOutputStream(int threshold, int initialBufferSize, java.lang.String prefix, java.lang.String suffix, java.io.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.- Parameters:
threshold
- The number of bytes at which to trigger an event.initialBufferSize
- The initial size of the in memory buffer.prefix
- Prefix to use for the temporary file.suffix
- Suffix to use for the temporary file.directory
- Temporary file directory.- Since:
- 2.5
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DeferredFileOutputStream
private DeferredFileOutputStream(int threshold, java.io.File outputFile, java.lang.String prefix, java.lang.String suffix, java.io.File directory, int initialBufferSize)
Constructs an instance of this class which will trigger an event at the specified threshold, and save data either to a file beyond that point.- Parameters:
threshold
- The number of bytes at which to trigger an event.outputFile
- The file to which data is saved beyond the threshold.prefix
- Prefix to use for the temporary file.suffix
- Suffix to use for the temporary file.directory
- Temporary file directory.initialBufferSize
- The initial size of the in memory buffer.
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Method Detail
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getStream
protected java.io.OutputStream getStream() throws java.io.IOException
Returns the current output stream. This may be memory based or disk based, depending on the current state with respect to the threshold.- Specified by:
getStream
in classThresholdingOutputStream
- Returns:
- The underlying output stream.
- Throws:
java.io.IOException
- if an error occurs.
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thresholdReached
protected void thresholdReached() throws java.io.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.- Specified by:
thresholdReached
in classThresholdingOutputStream
- Throws:
java.io.IOException
- if an error occurs.
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isInMemory
public boolean isInMemory()
Determines whether or not the data for this output stream has been retained in memory.- Returns:
true
if the data is available in memory;false
otherwise.
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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 returnsnull
.- Returns:
- The data for this output stream, or
null
if no such data is available.
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getFile
public java.io.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.- Returns:
- The file for this output stream, or
null
if no such file exists.
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close
public void close() throws java.io.IOException
Closes underlying output stream, and mark this as closed- Specified by:
close
in interfacejava.lang.AutoCloseable
- Specified by:
close
in interfacejava.io.Closeable
- Overrides:
close
in classThresholdingOutputStream
- Throws:
java.io.IOException
- if an error occurs.
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writeTo
public void writeTo(java.io.OutputStream out) throws java.io.IOException
Writes the data from this output stream to the specified output stream, after it has been closed.- Parameters:
out
- output stream to write to.- Throws:
java.io.IOException
- if this stream is not yet closed or an error occurs.
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