Class UpdateSensitiveLOBLocatorInputStream

java.lang.Object

java.io.InputStream

org.apache.derby.client.am.UpdateSensitiveLOBLocatorInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

Direct Known Subclasses:

UpdateSensitiveBlobLocatorInputStream, UpdateSensitiveClobLocatorInputStream

abstract class UpdateSensitiveLOBLocatorInputStream
extends InputStream

Super-class of the Update sensitive locator streams. Before a read operation if performed on the stream this stream verifies that the underlying LOB has not changed and if it has it recreates the specific streams. Since Locator streams are specific to Blob and Clob the sub-classes would take care of creating the appropriate streams.

Field Summary

Fields

Modifier and Type	Field	Description
protected ClientConnection	con
protected long	currentPos
private BufferedInputStream	is
protected long	length
private Lob	lob
private long	updateCount

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	UpdateSensitiveLOBLocatorInputStream(ClientConnection con, Lob lob, InputStream is)	Initializes the InputStream, updateCount, currentPos and the connection to the appropriate values.
protected	UpdateSensitiveLOBLocatorInputStream(ClientConnection con, Lob lob, InputStream is, long pos, long len)	Initializes the InputStream, updateCount, currentPos, length and the connection to the appropriate values.

Method Summary

Modifier and Type	Method	Description
void	close()
private void	identifyAndReplaceObseleteStream()	Verifies whether the current updateCount matches the updateCount of the LOB object and if it does not it recreates the stream.
int	read()
int	read(byte[] b, int off, int len)
protected abstract InputStream	reCreateStream()	Abstract method that will be implemented by the underlying streams specific to Clob and Blob.

Methods inherited from class InputStream

available, mark, markSupported, nullInputStream, read, readAllBytes, readNBytes, readNBytes, reset, skip, skipNBytes, transferTo

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

is

private BufferedInputStream is

con

protected ClientConnection con

lob

private Lob lob

updateCount

private long updateCount

currentPos

protected long currentPos

length

protected long length

Constructor Details

UpdateSensitiveLOBLocatorInputStream

protected UpdateSensitiveLOBLocatorInputStream(ClientConnection con,
 Lob lob,
 InputStream is)
                                        throws SqlException

Initializes the InputStream, updateCount, currentPos and the connection to the appropriate values.

Parameters:

con - connection to be used to read the Lob value from the server

lob - Lob object which could be a Blob or a Clob.

is - an InputStream that contains the appropriate locator stream instance.

Throws:

SqlException

UpdateSensitiveLOBLocatorInputStream

protected UpdateSensitiveLOBLocatorInputStream(ClientConnection con,
 Lob lob,
 InputStream is,
 long pos,
 long len)
                                        throws SqlException

Initializes the InputStream, updateCount, currentPos, length and the connection to the appropriate values.

Parameters:

con - connection to be used to read the Lob value from the server

lob - Lob object which could be a Blob or a Clob.

is - an InputStream that contains the appropriate locator stream instance.

pos - the position from which the first read begins.

len - the length in bytes of the partial value to be retrieved.

Throws:

SqlException

Method Details

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

See Also:

• InputStream.read()

read

public int read(byte[] b,
 int off,
 int len)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

See Also:

• InputStream.read(byte[], int, int)

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

Throws:

IOException

identifyAndReplaceObseleteStream

private void identifyAndReplaceObseleteStream()
                                       throws IOException

Verifies whether the current updateCount matches the updateCount of the LOB object and if it does not it recreates the stream.

Throws:

IOException - If any exception occurs upon Locator stream creation.

reCreateStream

protected abstract InputStream reCreateStream()
                                       throws SqlException

Abstract method that will be implemented by the underlying streams specific to Clob and Blob.

Throws:

SqlException