Class 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.

    • 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

      All Methods Instance Methods Abstract Methods Concrete Methods 
      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.
      protected abstract OutputStream getStream()
      Returns the underlying output stream, to which the corresponding OutputStream methods in this class will ultimately delegate.
      boolean isThresholdExceeded()
      Determines whether or not the configured threshold has been exceeded for this output stream.
      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.
    • 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

      • 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.
      • 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.
      • 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.