org.apache.derby.impl.drda
Class EXTDTAReaderInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by org.apache.derby.impl.drda.EXTDTAReaderInputStream
All Implemented Interfaces:
java.io.Closeable
Direct Known Subclasses:
LayerBStreamedEXTDTAReaderInputStream, StandardEXTDTAReaderInputStream

abstract class EXTDTAReaderInputStream
extends java.io.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 Summary
protected  boolean isLayerBStream
          Whether or not the subclass is a layer B stream.
protected  boolean readStatusByte
          Whether or not to read the trailing Derby-specific status byte.
private  byte status
          The status Derby-specific status byte, if any.
private  boolean statusSet
          Tells if the status byte has been set.
private  boolean suppressException
          Whether or not to suppress the exception when an error is indicated by the status byte.
 
Constructor Summary
protected EXTDTAReaderInputStream(boolean layerB, boolean readStatusByte)
          Initializes the class.
 
Method Summary
protected  void checkStatus(int clientStatus)
          Interprets the Derby-specific status byte, and throws an exception if an error condition has been detected on the client.
 byte getStatus()
          Returns the status byte.
 boolean isLayerBStream()
           
 boolean isStatusSet()
          Returns whether the status has been set or not.
protected abstract  void onClientSideStreamingError()
          Performs necessary clean up when an error is signalled by the client.
private  void setStatus(int status)
          Saves the status byte read off the wire.
(package private)  void setSuppressException(boolean flag)
          Sets whether or not to suppress the exception when setting the status.
(package private) static void throwEXTDTATransferException(int status)
          Throws an exception as mandated by the EXTDTA status byte.
 
Methods inherited from class java.io.InputStream
available, close, mark, markSupported, read, read, read, reset, skip
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

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:
checkStatus(int)

status

private byte status
The status Derby-specific status byte, if any.

See Also:
isStatusSet()

suppressException

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

Constructor Detail

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 Detail

setStatus

private void setStatus(int status)
Saves the status byte read off the wire.

Parameters:
status - the status
See Also:
DRDAConstants

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 java.io.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:
java.io.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 java.io.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:
java.io.IOException - the exception generated based on the status byte

Built on Thu 2010-12-23 20:49:13+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.