org.apache.commons.io.output

Class DeferredFileOutputStream

java.lang.Object

java.io.OutputStream

org.apache.commons.io.output.ThresholdingOutputStream

org.apache.commons.io.output.DeferredFileOutputStream

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.

To build an instance, see DeferredFileOutputStream.Builder.

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).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DeferredFileOutputStream.Builder Builds a new DeferredFileOutputStream instance.

Constructor Summary

Constructors

Constructor and Description
DeferredFileOutputStream(int threshold, java.io.File outputFile) Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()
DeferredFileOutputStream(int threshold, int initialBufferSize, java.io.File outputFile) Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()
DeferredFileOutputStream(int threshold, int initialBufferSize, java.lang.String prefix, java.lang.String suffix, java.io.File directory) Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()
DeferredFileOutputStream(int threshold, java.lang.String prefix, java.lang.String suffix, java.io.File directory) Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()

Method Summary

Modifier and Type	Method and Description
static DeferredFileOutputStream.Builder	builder() Constructs a new DeferredFileOutputStream.Builder.
void	close() Closes underlying output stream, and mark this as closed
byte[]	getData() Gets the data for this output stream as an array of bytes, assuming that the data has been retained in memory.
java.io.File	getFile() Gets either the output file specified in the constructor or the temporary file created or null.
boolean	isInMemory() Tests whether or not the data for this output stream has been retained in memory.
java.io.InputStream	toInputStream() Converts the current contents of this byte stream to an InputStream.
void	writeTo(java.io.OutputStream outputStream) 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

flush, getByteCount, getThreshold, isThresholdExceeded, write, write, write

Methods inherited from class java.lang.Object

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

Constructor Detail

DeferredFileOutputStream

@Deprecated
public DeferredFileOutputStream(int threshold,
                                            java.io.File outputFile)

Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()

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 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.

DeferredFileOutputStream

@Deprecated
public DeferredFileOutputStream(int threshold,
                                            int initialBufferSize,
                                            java.io.File outputFile)

Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()

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

DeferredFileOutputStream

@Deprecated
public DeferredFileOutputStream(int threshold,
                                            int initialBufferSize,
                                            java.lang.String prefix,
                                            java.lang.String suffix,
                                            java.io.File directory)

Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()

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

DeferredFileOutputStream

@Deprecated
public DeferredFileOutputStream(int threshold,
                                            java.lang.String prefix,
                                            java.lang.String suffix,
                                            java.io.File directory)

Deprecated. Use builder(), DeferredFileOutputStream.Builder, and DeferredFileOutputStream.Builder.get()

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

Method Detail

builder

public static DeferredFileOutputStream.Builder builder()

Constructs a new DeferredFileOutputStream.Builder.

Returns:

a new DeferredFileOutputStream.Builder.

Since:

2.12.0

close

public void close()
           throws java.io.IOException

Closes underlying output stream, and mark this as closed

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class ThresholdingOutputStream

Throws:

java.io.IOException - if an error occurs.

getData

public byte[] getData()

Gets 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.

Returns:

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

getFile

public java.io.File getFile()

Gets 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.

isInMemory

public boolean isInMemory()

Tests 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.

toInputStream

public java.io.InputStream toInputStream()
                                  throws java.io.IOException

Converts the current contents of this byte stream to an InputStream. If the data for this output stream has been retained in memory, the returned stream is backed by buffers of this stream, avoiding memory allocation and copy, thus saving space and time.
Otherwise, the returned stream will be one that is created from the data that has been committed to disk.

Returns:

the current contents of this output stream.

Throws:

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

Since:

2.9.0

See Also:

ByteArrayOutputStream.toInputStream()

writeTo

public void writeTo(java.io.OutputStream outputStream)
             throws java.io.IOException

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

Parameters:

outputStream - output stream to write to.

Throws:

java.lang.NullPointerException - if the OutputStream is null.

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