Package org.apache.derby.client.am

Class UpdateSensitiveClobLocatorReader

java.lang.Object

java.io.Reader

org.apache.derby.client.am.UpdateSensitiveClobLocatorReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

class UpdateSensitiveClobLocatorReader
extends Reader

Wraps a Buffered Clob locator reader and watches out for updates on the Clob associated with it. Before a read operation is performed on the Reader this stream verifies that the underlying Clob has not changed and if it has it recreates the specific streams.

Field Summary

Fields

Modifier and Type	Field	Description
private ClientClob	clob
private ClientConnection	con
private long	currentPos
private long	length
private BufferedReader	r
private long	updateCount

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	UpdateSensitiveClobLocatorReader(ClientConnection con, ClientClob clob)	Initializes the Reader, updateCount, currentPos and the connection to the appropriate values.
protected	UpdateSensitiveClobLocatorReader(ClientConnection con, ClientClob clob, long pos, long len)	Initializes the Reader, 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 Clob object and if it does not it recreates the stream.
int	read()
int	read(char[] c, int off, int len)
private Reader	reCreateStream()	Re-creates the underlying Locator stream with the current position and the length values if specified.

Methods inherited from class java.io.Reader

mark, markSupported, nullReader, read, read, ready, reset, skip, transferTo

Methods inherited from class java.lang.Object

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

Field Details

r

private BufferedReader r

con

private ClientConnection con

clob

private ClientClob clob

updateCount

private long updateCount

currentPos

private long currentPos

length

private long length

Constructor Details

UpdateSensitiveClobLocatorReader

protected UpdateSensitiveClobLocatorReader(ClientConnection con,
 ClientClob clob)
                                    throws SqlException

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

Parameters:

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

clob - the Clob object associated with this stream.

Throws:

SqlException

UpdateSensitiveClobLocatorReader

protected UpdateSensitiveClobLocatorReader(ClientConnection con,
 ClientClob clob,
 long pos,
 long len)
                                    throws SqlException

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

Parameters:

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

clob - the Clob object associated with this reader.

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

Overrides:

read in class Reader

Throws:

IOException

See Also:

• Reader.read()

read

public int read(char[] c,
 int off,
 int len)
         throws IOException

Specified by:

read in class Reader

Throws:

IOException

See Also:

• Reader.read(char[], int, int)

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class Reader

Throws:

IOException

See Also:

• Reader.close()

identifyAndReplaceObseleteStream

private void identifyAndReplaceObseleteStream()
                                       throws IOException

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

Throws:

IOException - If any exception occurs upon Locator stream creation.

reCreateStream

private Reader reCreateStream()
                       throws SqlException

Re-creates the underlying Locator stream with the current position and the length values if specified.

Throws:

SqlException