org.apache.derby.client.am

Class ClobLocatorReader

java.lang.Object

java.io.Reader

org.apache.derby.client.am.ClobLocatorReader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable

public class ClobLocatorReader
extends java.io.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 efficieny #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 and Description
private Clob	clob The Clob to be accessed.
private Connection	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 long	maxPos Position in Clob where to stop reading.

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor and Description
ClobLocatorReader(Connection connection, Clob clob) Create an Reader for reading the Clob value represented by the given locator based Clob object.
ClobLocatorReader(Connection connection, Clob 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 and 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 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

connection

private final Connection connection

Connection used to read Clob from server.

clob

private final Clob 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 Detail

ClobLocatorReader

public ClobLocatorReader(Connection connection,
                         Clob 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

public ClobLocatorReader(Connection connection,
                         Clob 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 Detail

read

public int read()
         throws java.io.IOException

Overrides:

read in class java.io.Reader

Throws:

java.io.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 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 interface java.lang.AutoCloseable

Specified by:

close in class java.io.Reader

Throws:

java.io.IOException

See Also:

Reader.close()

checkClosed

private void checkClosed()
                  throws java.io.IOException

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

Throws:

java.io.IOException - if isClosed = true.

readCharacters

private char[] readCharacters(int len)
                       throws java.io.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:

java.io.IOException - Wrapped SqlException if reading from server fails.