Class BlobLocatorInputStream

java.lang.Object

java.io.InputStream

org.apache.derby.client.am.BlobLocatorInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

class BlobLocatorInputStream
extends InputStream

An InputStream that will use an locator to fetch the Blob value from the server.

Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException.

This InputStream implementation is pretty basic. No buffering of data is done. Hence, for efficiency #read(byte[]) 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 ClientBlob	blob	The Blob to be accessed.
private final ClientConnection	connection	Connection used to read Blob from server.
private long	currentPos	Current position in the underlying Blob.
private final long	maxPos	Position in Blob where to stop reading. maxPos starts counting from 1.

Constructor Summary

Constructors

Constructor	Description
BlobLocatorInputStream(ClientConnection connection, ClientBlob blob)	Create an InputStream for reading the Blob value represented by the given locator based Blob object.
BlobLocatorInputStream(ClientConnection connection, ClientBlob blob, long position, long length)	Create an InputStream for reading the Blob value represented by the given locator based Blob object.

Method Summary

Modifier and Type	Method	Description
int	read()
int	read(byte[] b, int off, int len)
private byte[]	readBytes(int len)	Read the next len bytes of the Blob value from the server.

Methods inherited from class InputStream

available, close, 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

connection

private final ClientConnection connection

Connection used to read Blob from server.

blob

private final ClientBlob blob

The Blob to be accessed.

currentPos

private long currentPos

Current position in the underlying Blob. Blobs are indexed from 1

maxPos

private final long maxPos

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

Constructor Details

BlobLocatorInputStream

BlobLocatorInputStream(ClientConnection connection,
 ClientBlob blob)
                throws SqlException

Create an InputStream for reading the Blob value represented by the given locator based Blob object.

Parameters:

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

blob - Blob object that contains locator for the Blob value on the server.

Throws:

SqlException - if an error occurs when obtaining the length of the Blob.

BlobLocatorInputStream

BlobLocatorInputStream(ClientConnection connection,
 ClientBlob blob,
 long position,
 long length)
                throws SqlException

Create an InputStream for reading the Blob value represented by the given locator based Blob object.

Parameters:

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

blob - Blob object that contains locator for the Blob value on the server.

position - the position in the Blob of the first byte to read.

length - the maximum number of bytes to read from the Blob.

Throws:

SqlException - if an error occurs when obtaining the length of the Blob.

Method Details

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

See Also:

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

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)

readBytes

private byte[] readBytes(int len)
                  throws IOException

Read the next len bytes of the Blob value from the server.

Parameters:

len - number of bytes to read

Returns:

byte[] containing the read bytes

Throws:

IOException - Wrapped SqlException if reading from server fails.