Package org.apache.commons.io.output

Class ThresholdingOutputStream

java.lang.Object
java.io.OutputStream
org.apache.commons.io.output.ThresholdingOutputStream
All Implemented Interfaces:
Closeable, Flushable, AutoCloseable
Direct Known Subclasses:
DeferredFileOutputStream
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.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final int
    threshold
    The threshold at which the event will be triggered.
    private boolean
    thresholdExceeded
    Whether or not the configured threshold has been exceeded.
    private long
    written
    The number of bytes written to the output stream.

  • Constructor Summary

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

  • Method Summary

    Modifier and Type
    Method
    Description
    protected void
    checkThreshold(int count)
    Checks to see if writing the specified number of bytes would cause the configured threshold to be exceeded.
    void
    close()
    Closes this output stream and releases any system resources associated with this stream.
    void
    flush()
    Flushes this output stream and forces any buffered output bytes to be written out.
    long
    getByteCount()
    Returns the number of bytes that have been written to this output stream.
    protected abstract OutputStream
    getStream()
    Returns the underlying output stream, to which the corresponding OutputStream methods in this class will ultimately delegate.
    int
    getThreshold()
    Returns the threshold, in bytes, at which an event will be triggered.
    boolean
    isThresholdExceeded()
    Determines whether or not the configured threshold has been exceeded for this output stream.
    protected void
    resetByteCount()
    Resets the byteCount to zero.
    protected void
    setByteCount(long count)
    Sets the byteCount to count.
    protected abstract void
    thresholdReached()
    Indicates that the configured threshold has been reached, and that a subclass should take whatever action necessary on this event.
    void
    write(byte[] b)
    Writes b.length bytes from the specified byte array to this output stream.
    void
    write(byte[] b, int off, int len)
    Writes len bytes from the specified byte array starting at offset off to this output stream.
    void
    write(int b)
    Writes the specified byte to this output stream.

    Methods inherited from class java.io.OutputStream

    nullOutputStream

    Methods inherited from class java.lang.Object

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

  • Field Details

    • threshold

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

    • written

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

    • thresholdExceeded

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

  • Constructor Details

    • 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 Details

    • write

      public void write(int b) throws IOException
      Writes the specified byte to this output stream.
      Specified by:
      write in class OutputStream
      Parameters:
      b - The byte to be written.
      Throws:
      IOException - if an error occurs.

    • write

      public void write(byte[] b) throws IOException
      Writes b.length bytes from the specified byte array to this output stream.
      Overrides:
      write in class OutputStream
      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) throws IOException
      Writes len bytes from the specified byte array starting at offset off to this output stream.
      Overrides:
      write in class OutputStream
      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.

    • flush

      public void flush() throws IOException
      Flushes this output stream and forces any buffered output bytes to be written out.
      Specified by:
      flush in interface Flushable
      Overrides:
      flush in class OutputStream
      Throws:
      IOException - if an error occurs.

    • close

      public void close() throws IOException
      Closes this output stream and releases any system resources associated with this stream.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class OutputStream
      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.

    • getByteCount

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

    • 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.

    • checkThreshold

      protected void checkThreshold(int count) throws IOException
      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.

    • resetByteCount

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

    • setByteCount

      protected void setByteCount(long count)
      Sets the byteCount to count. Useful for re-opening an output stream that has previously been written to.
      Parameters:
      count - The number of bytes that have already been written to the output stream
      Since:
      2.5

    • getStream

      protected abstract OutputStream getStream() throws IOException
      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.

    • thresholdReached

      protected abstract void thresholdReached() throws IOException
      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.