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java.lang.Object java.io.OutputStream org.apache.commons.io.output.ThresholdingOutputStream org.apache.commons.io.output.DeferredFileOutputStream
public class DeferredFileOutputStream
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).
Constructor Summary | |
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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. |
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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. |
Method Summary | |
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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. |
Methods inherited from class org.apache.commons.io.output.ThresholdingOutputStream |
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checkThreshold, flush, getByteCount, getThreshold, isThresholdExceeded, resetByteCount, write, write, write |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public DeferredFileOutputStream(int threshold, File outputFile)
threshold
- The number of bytes at which to trigger an event.outputFile
- The file to which data is saved beyond the threshold.public DeferredFileOutputStream(int threshold, String prefix, String suffix, File directory)
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.Method Detail |
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protected OutputStream getStream() throws IOException
getStream
in class ThresholdingOutputStream
IOException
- if an error occurs.protected void thresholdReached() throws IOException
thresholdReached
in class ThresholdingOutputStream
IOException
- if an error occurs.public boolean isInMemory()
true
if the data is available in memory;
false
otherwise.public byte[] getData()
null
.
null
if no such
data is available.public File getFile()
If the constructor specifying the file is used then it returns that same output file, even when threashold has not been reached.
If constructor specifying a temporary file prefix/suffix is used
then the temporary file created once the threashold is reached is returned
If the threshold was not reached then null
is returned.
null
if no such
file exists.public void close() throws IOException
close
in interface Closeable
close
in class ThresholdingOutputStream
IOException
- if an error occurs.public void writeTo(OutputStream out) throws IOException
out
- output stream to write to.
IOException
- if this stream is not yet closed or an error occurs.
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