Class OffloadingOutputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable

    class OffloadingOutputStream
    extends org.apache.commons.io.output.ThresholdingOutputStream
    Offloads to disk when a given memory consumption has been reacehd
    • Field Summary

      Fields 
      Modifier and Type Field Description
      private boolean closed
      True when close() has been called successfully.
      private java.io.OutputStream currentOutputStream
      The output stream to which data will be written at any given time.
      private java.io.File directory
      The directory to use for temporary files.
      private ByteArrayOutputStream memoryOutputStream
      The output stream to which data will be written prior to the theshold being reached.
      private java.io.File outputFile
      The file to which output will be directed if the threshold is exceeded.
      private java.lang.String prefix
      The temporary file prefix.
      private java.lang.String suffix
      The temporary file suffix.
    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private OffloadingOutputStream​(int threshold, java.io.File outputFile, java.lang.String prefix, java.lang.String suffix, java.io.File directory)
      Constructs an instance of this class which will trigger an event at the specified threshold, and save data either to a file beyond that point.
        OffloadingOutputStream​(int threshold, java.lang.String prefix, java.lang.String suffix, java.io.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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      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.
      java.io.File getFile()
      Returns either the output file specified in the constructor or the temporary file created or null.
      java.io.InputStream getInputStream()  
      protected java.io.OutputStream getStream()
      Returns the current output stream.
      protected void thresholdReached()
      Switches the underlying output stream from a memory based stream to one that is backed by disk.
      • Methods inherited from class org.apache.commons.io.output.ThresholdingOutputStream

        checkThreshold, flush, getByteCount, getThreshold, isThresholdExceeded, resetByteCount, setByteCount, write, write, write
      • 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 Detail

      • memoryOutputStream

        private ByteArrayOutputStream memoryOutputStream
        The output stream to which data will be written prior to the theshold being reached.
      • currentOutputStream

        private java.io.OutputStream currentOutputStream
        The output stream to which data will be written at any given time. This will always be one of memoryOutputStream or diskOutputStream.
      • outputFile

        private java.io.File outputFile
        The file to which output will be directed if the threshold is exceeded.
      • prefix

        private final java.lang.String prefix
        The temporary file prefix.
      • suffix

        private final java.lang.String suffix
        The temporary file suffix.
      • directory

        private final java.io.File directory
        The directory to use for temporary files.
      • closed

        private boolean closed
        True when close() has been called successfully.
    • Constructor Detail

      • OffloadingOutputStream

        public OffloadingOutputStream​(int threshold,
                                      java.lang.String prefix,
                                      java.lang.String suffix,
                                      java.io.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.
        Parameters:
        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.
        Since:
        1.4
      • OffloadingOutputStream

        private OffloadingOutputStream​(int threshold,
                                       java.io.File outputFile,
                                       java.lang.String prefix,
                                       java.lang.String suffix,
                                       java.io.File directory)
        Constructs an instance of this class which will trigger an event at the specified threshold, and save data either to a file beyond that point.
        Parameters:
        threshold - The number of bytes at which to trigger an event.
        outputFile - The file to which data is saved beyond the threshold.
        prefix - Prefix to use for the temporary file.
        suffix - Suffix to use for the temporary file.
        directory - Temporary file directory.
    • Method Detail

      • getStream

        protected java.io.OutputStream getStream()
                                          throws java.io.IOException
        Returns the current output stream. This may be memory based or disk based, depending on the current state with respect to the threshold.
        Specified by:
        getStream in class org.apache.commons.io.output.ThresholdingOutputStream
        Returns:
        The underlying output stream.
        Throws:
        java.io.IOException - if an error occurs.
      • thresholdReached

        protected void thresholdReached()
                                 throws java.io.IOException
        Switches the underlying output stream from a memory based stream to one that is backed by disk. This is the point at which we realise that too much data is being written to keep in memory, so we elect to switch to disk-based storage.
        Specified by:
        thresholdReached in class org.apache.commons.io.output.ThresholdingOutputStream
        Throws:
        java.io.IOException - if an error occurs.
      • getInputStream

        public java.io.InputStream getInputStream()
                                           throws java.io.IOException
        Throws:
        java.io.IOException
      • getData

        public byte[] getData()
        Returns the data for this output stream as an array of bytes, assuming that the data has been retained in memory. If the data was written to disk, this method returns null.
        Returns:
        The data for this output stream, or null if no such data is available.
      • getFile

        public java.io.File getFile()
        Returns either the output file specified in the constructor or the temporary file created or null.

        If the constructor specifying the file is used then it returns that same output file, even when threshold has not been reached.

        If constructor specifying a temporary file prefix/suffix is used then the temporary file created once the threshold is reached is returned If the threshold was not reached then null is returned.

        Returns:
        The file for this output stream, or null if no such file exists.
      • close

        public void close()
                   throws java.io.IOException
        Closes underlying output stream, and mark this as closed
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class org.apache.commons.io.output.ThresholdingOutputStream
        Throws:
        java.io.IOException - if an error occurs.