org.apache.commons.io.output

Class ThresholdingOutputStream

  • All Implemented Interfaces:
    Closeable, Flushable, AutoCloseable
    Direct Known Subclasses:
    DeferredFileOutputStream

    public 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.

    • Method Summary

      All Methods  Instance Methods  Concrete Methods 
      Modifier and Type Method and 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 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 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.
    • 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.
      • ThresholdingOutputStream

        public ThresholdingOutputStream(int threshold,
                                        IOConsumer<ThresholdingOutputStream> thresholdConsumer,
                                        IOFunction<ThresholdingOutputStream,OutputStream> outputStreamGetter)
        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.
        thresholdConsumer - Accepts reaching the threshold.
        outputStreamGetter - Gets the output stream.
        Since:
        2.9.0
    • Method Detail

      • 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.
      • 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 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.
      • 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.
      • 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
      • thresholdReached

        protected 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.
      • 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.
      • 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.

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