Class ClobLocatorReader

java.lang.Object

java.io.Reader

org.apache.derby.client.am.ClobLocatorReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

class ClobLocatorReader
extends Reader

An Reader that will use an locator to fetch the Clob value from the server.

This Reader implementation is pretty basic. No buffering of data is done. Hence, for efficiency #read(char[]) should be used instead of #read(). Marks are not supported, but it should be pretty simple to extend the implementation to support this. A more efficient skip implementation should also be straight-forward.

Field Summary

Fields

Modifier and Type	Field	Description
private final ClientClob	clob	The Clob to be accessed.
private final ClientConnection	connection	Connection used to read Clob from server.
private long	currentPos	Current position in the underlying Clob.
private boolean	isClosed	Stores the information to whether this Reader has been closed or not.
private final long	maxPos	Position in Clob where to stop reading. maxPos starts counting from 1.

Fields inherited from class Reader

lock

Constructor Summary

Constructors

Constructor	Description
ClobLocatorReader(ClientConnection connection, ClientClob clob)	Create an Reader for reading the Clob value represented by the given locator based Clob object.
ClobLocatorReader(ClientConnection connection, ClientClob clob, long pos, long len)	Create an Reader for reading the Clob value represented by the given locator based Clob object.

Method Summary

Modifier and Type	Method	Description
private void	checkClosed()	Check to see if this Reader is closed.
void	close()
int	read()
int	read(char[] c, int off, int len)
private char[]	readCharacters(int len)	Read the next len characters of the Clob value from the server.

Methods inherited from class Reader

mark, markSupported, nullReader, of, read, read, readAllAsString, readAllLines, ready, reset, skip, transferTo

Methods inherited from class Object

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

Field Details

connection

private final ClientConnection connection

Connection used to read Clob from server.

clob

private final ClientClob clob

The Clob to be accessed.

currentPos

private long currentPos

Current position in the underlying Clob. Clobs are indexed from 1

maxPos

private final long maxPos

Position in Clob where to stop reading. maxPos starts counting from 1.

isClosed

private boolean isClosed

Stores the information to whether this Reader has been closed or not. Is set to true if close() has been called. Is false otherwise.

Constructor Details

ClobLocatorReader

ClobLocatorReader(ClientConnection connection,
 ClientClob clob)
           throws SqlException

Create an Reader for reading the Clob value represented by the given locator based Clob object.

Parameters:

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

clob - Clob object that contains locator for the Clob value on the server.

Throws:

SqlException

ClobLocatorReader

ClobLocatorReader(ClientConnection connection,
 ClientClob clob,
 long pos,
 long len)
           throws SqlException

Create an Reader for reading the Clob value represented by the given locator based Clob object.

Parameters:

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

clob - Clob object that contains locator for the Clob value on the server.

pos - The offset to the first character of the partial value to be retrieved.

len - The length in characters 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:

• This method fetches one character at a time from the server. For more efficient retrieval, use #read(char[]).

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()

checkClosed

private void checkClosed()
                  throws IOException

Check to see if this Reader is closed. If it is closed throw an IOException that states that the stream is closed.

Throws:

IOException - if isClosed = true.

readCharacters

private char[] readCharacters(int len)
                       throws IOException

Read the next len characters of the Clob value from the server.

Parameters:

len - number of characters to read.

Returns:

char[] containing the read characters.

Throws:

IOException - Wrapped SqlException if reading from server fails.