org.apache.derby.client.am
Class UpdateSensitiveClobLocatorReader

java.lang.Object
  java.io.Reader
      org.apache.derby.client.am.UpdateSensitiveClobLocatorReader

All Implemented Interfaces:

java.io.Closeable, java.lang.Readable

public class UpdateSensitiveClobLocatorReader
extends java.io.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

private Clob	clob
private Connection	con
private long	currentPos
private long	length
private java.io.BufferedReader	r
private long	updateCount

Fields inherited from class java.io.Reader

lock

Constructor Summary

protected	UpdateSensitiveClobLocatorReader(Connection con, Clob clob) Initializes the Reader, updateCount, currentPos and the connection to the appropriate values.
protected	UpdateSensitiveClobLocatorReader(Connection con, Clob clob, long pos, long len) Initializes the Reader, updateCount, currentPos, length and the connection to the appropriate values.

Method Summary

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)
protected java.io.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, read, read, ready, reset, skip

Methods inherited from class java.lang.Object

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

Field Detail

r

private java.io.BufferedReader r

con

private Connection con

clob

private Clob clob

updateCount

private long updateCount

currentPos

private long currentPos

length

private long length

Constructor Detail

UpdateSensitiveClobLocatorReader

protected UpdateSensitiveClobLocatorReader(Connection con,
                                           Clob 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(Connection con,
                                           Clob 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 Detail

read

public int read()
         throws java.io.IOException

Overrides:

read in class java.io.Reader

Throws:

java.io.IOException

See Also:

Reader.read()

read

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

Specified by:

read in class java.io.Reader

Throws:

java.io.IOException

See Also:

Reader.read(char[], int, int)

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.io.Closeable

Specified by:

close in class java.io.Reader

Throws:

java.io.IOException

See Also:

Reader.close()

identifyAndReplaceObseleteStream

private void identifyAndReplaceObseleteStream()
                                       throws java.io.IOException

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

Throws:

java.io.IOException - If any exception occurs upon Locator stream creation.

reCreateStream

protected java.io.Reader reCreateStream()
                                 throws SqlException

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

Throws:

SqlException