Class EXTDTAReaderInputStream

java.lang.Object
java.io.InputStream
org.apache.derby.impl.drda.EXTDTAReaderInputStream
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
LayerBStreamedEXTDTAReaderInputStream, StandardEXTDTAReaderInputStream
abstract class EXTDTAReaderInputStream extends InputStream
Implementation of InputStream which get EXTDTA from the DDMReader.

This class can be used to stream LOBs from Network client to the Network server.

To be able to correctly stream data from the client without reading the while value up front, a trailing Derby-specific status byte was introduced (version 10.6). It is used by the client to tell the server if the data it received was valid, or if it detected an error while streaming the data. The DRDA protocol, or at least Derby's implementation of it, doesn't enable the client to inform the server about the error whilst streaming (there is a mechanism in DRDA to interrupt a running request, but it didn't seem like a feasible approach in this case).

  • Field Details

    • isLayerBStream

      protected final boolean isLayerBStream
      Whether or not the subclass is a layer B stream.

    • readStatusByte

      protected final boolean readStatusByte
      Whether or not to read the trailing Derby-specific status byte.

    • statusSet

      private boolean statusSet
      Tells if the status byte has been set.
      See Also:

    • status

      private byte status
      The status Derby-specific status byte, if any.
      See Also:

    • suppressException

      private boolean suppressException
      Whether or not to suppress the exception when an error is indicated by the status byte.

  • Constructor Details

    • EXTDTAReaderInputStream

      protected EXTDTAReaderInputStream(boolean layerB, boolean readStatusByte)
      Initializes the class.
      Parameters:
      layerB - whether or not DDM layer B streaming is being used
      readStatusByte - whether or not to read the trailing Derby-specific status byte

  • Method Details

    • setStatus

      private void setStatus(int status)
      Saves the status byte read off the wire.
      Parameters:
      status - the status
      See Also:

    • isStatusSet

      public boolean isStatusSet()
      Returns whether the status has been set or not.
      Returns:
      true if set, false if not.

    • getStatus

      public byte getStatus()
      Returns the status byte.

      NOTE: Check if the status byte has been set by calling isStatusSet().

      Returns:
      The status byte.

    • setSuppressException

      void setSuppressException(boolean flag)
      Sets whether or not to suppress the exception when setting the status.
      Parameters:
      flag - true to suppress, false to throw exception if an error condition is indicated by the status flag

    • isLayerBStream

      public boolean isLayerBStream()

    • checkStatus

      protected void checkStatus(int clientStatus) throws IOException
      Interprets the Derby-specific status byte, and throws an exception if an error condition has been detected on the client.
      Parameters:
      clientStatus - the status flag sent by the client
      Throws:
      IOException - if the status byte indicates an error condition

    • onClientSideStreamingError

      protected abstract void onClientSideStreamingError()
      Performs necessary clean up when an error is signalled by the client.

    • throwEXTDTATransferException

      static void throwEXTDTATransferException(int status) throws IOException
      Throws an exception as mandated by the EXTDTA status byte.
      Parameters:
      status - the EXTDTA status byte received from the client, should not be DRDAConstants.STREAM_OK
      Throws:
      IOException - the exception generated based on the status byte