org.apache.commons.io.output

Class ThresholdingOutputStream

public abstract class ThresholdingOutputStream extends OutputStream

An output stream which triggers an event when a specified number of bytes of data have been written to it. The event can be used, for example, to throw an exception if a maximum has been reached, or to switch the underlying stream type when the threshold is exceeded.

This class overrides all OutputStream methods. However, these overrides ultimately call the corresponding methods in the underlying output stream implementation.

NOTE: This implementation may trigger the event before the threshold is actually reached, since it triggers when a pending write operation would cause the threshold to be exceeded.

Version: $Id: ThresholdingOutputStream.java 540714 2007-05-22 19:39:44Z niallp $

Author: Martin Cooper

Field Summary
intthreshold
The threshold at which the event will be triggered.
booleanthresholdExceeded
Whether or not the configured threshold has been exceeded.
longwritten
The number of bytes written to the output stream.
Constructor Summary
ThresholdingOutputStream(int threshold)
Constructs an instance of this class which will trigger an event at the specified threshold.
Method Summary
protected voidcheckThreshold(int count)
Checks to see if writing the specified number of bytes would cause the configured threshold to be exceeded.
voidclose()
Closes this output stream and releases any system resources associated with this stream.
voidflush()
Flushes this output stream and forces any buffered output bytes to be written out.
longgetByteCount()
Returns the number of bytes that have been written to this output stream.
protected abstract OutputStreamgetStream()
Returns the underlying output stream, to which the corresponding OutputStream methods in this class will ultimately delegate.
intgetThreshold()
Returns the threshold, in bytes, at which an event will be triggered.
booleanisThresholdExceeded()
Determines whether or not the configured threshold has been exceeded for this output stream.
protected voidresetByteCount()
Resets the byteCount to zero.
protected abstract voidthresholdReached()
Indicates that the configured threshold has been reached, and that a subclass should take whatever action necessary on this event.
voidwrite(int b)
Writes the specified byte to this output stream.
voidwrite(byte[] b)
Writes b.length bytes from the specified byte array to this output stream.
voidwrite(byte[] b, int off, int len)
Writes len bytes from the specified byte array starting at offset off to this output stream.

Field Detail

threshold

private int threshold
The threshold at which the event will be triggered.

thresholdExceeded

private boolean thresholdExceeded
Whether or not the configured threshold has been exceeded.

written

private long written
The number of bytes written to the output stream.

Constructor Detail

ThresholdingOutputStream

public ThresholdingOutputStream(int threshold)
Constructs an instance of this class which will trigger an event at the specified threshold.

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

Method Detail

checkThreshold

protected void checkThreshold(int count)
Checks to see if writing the specified number of bytes would cause the configured threshold to be exceeded. If so, triggers an event to allow a concrete implementation to take action on this.

Parameters: count The number of bytes about to be written to the underlying output stream.

Throws: IOException if an error occurs.

close

public void close()
Closes this output stream and releases any system resources associated with this stream.

Throws: IOException if an error occurs.

flush

public void flush()
Flushes this output stream and forces any buffered output bytes to be written out.

Throws: IOException if an error occurs.

getByteCount

public long getByteCount()
Returns the number of bytes that have been written to this output stream.

Returns: The number of bytes written.

getStream

protected abstract OutputStream getStream()
Returns the underlying output stream, to which the corresponding OutputStream methods in this class will ultimately delegate.

Returns: The underlying output stream.

Throws: IOException if an error occurs.

getThreshold

public int getThreshold()
Returns the threshold, in bytes, at which an event will be triggered.

Returns: The threshold point, in bytes.

isThresholdExceeded

public boolean isThresholdExceeded()
Determines whether or not the configured threshold has been exceeded for this output stream.

Returns: true if the threshold has been reached; false otherwise.

resetByteCount

protected void resetByteCount()
Resets the byteCount to zero. You can call this from thresholdReached if you want the event to be triggered again.

thresholdReached

protected abstract void thresholdReached()
Indicates that the configured threshold has been reached, and that a subclass should take whatever action necessary on this event. This may include changing the underlying output stream.

Throws: IOException if an error occurs.

write

public void write(int b)
Writes the specified byte to this output stream.

Parameters: b The byte to be written.

Throws: IOException if an error occurs.

write

public void write(byte[] b)
Writes b.length bytes from the specified byte array to this output stream.

Parameters: b The array of bytes to be written.

Throws: IOException if an error occurs.

write

public void write(byte[] b, int off, int len)
Writes len bytes from the specified byte array starting at offset off to this output stream.

Parameters: b The byte array from which the data will be written. off The start offset in the byte array. len The number of bytes to write.

Throws: IOException if an error occurs.

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