org.hsqldb.jdbc

Class jdbcBlob

public class jdbcBlob extends Object implements Blob

The representation (mapping) in the Java^TM programming language of an SQL BLOB value.

Provides methods for getting the length of an SQL BLOB (Binary Large Object) value, for materializing a BLOB value on the client, and for determining the position of an octet sequence (byte pattern) within a BLOB value.

HSQLDB-Specific Information:

Including 1.8.x, the HSQLDB driver does not implement Blob using an SQL locator(BLOB). That is, an HSQLDB Blob object does not contain a logical pointer to SQL BLOB data; rather it directly contains a representation of the data (a byte array). As a result, an HSQLDB Blob object is itself valid beyond the duration of the transaction in which is was created, although it does not necessarily represent a corresponding value on the database.

Currently, the interface methods for updating a BLOB value are unsupported. However, the truncate method is supported for local use.

Since: JDK 1.2, HSQLDB 1.7.2

Author: james house jhouse@part.net boucherb@users

Constructor Summary
	jdbcBlob(byte[] data) Constructs a new jdbcBlob instance wrapping the given octet sequence.

Method Summary
InputStream	getBinaryStream() Retrieves the `BLOB` value designated by this `Blob` instance as a stream.
byte[]	getBytes(long pos, int length) Retrieves all or part of the `BLOB` value that this `Blob` object represents, as an array of bytes.
long	length() Returns the number of bytes in the `BLOB` value designated by this `Blob` object.
long	position(byte[] pattern, long start) Retrieves the byte position at which the specified byte array `pattern` begins within the `BLOB` value that this `Blob` object represents.
long	position(Blob pattern, long start) Retrieves the byte position in the `BLOB` value designated by this `Blob` object at which `pattern` begins.
OutputStream	setBinaryStream(long pos) Retrieves a stream that can be used to write to the `BLOB` value that this `Blob` object represents.
int	setBytes(long pos, byte[] bytes) Writes the given array of bytes to the `BLOB` value that this `Blob` object represents, starting at position `pos`, and returns the number of bytes written.
int	setBytes(long pos, byte[] bytes, int offset, int len) Writes all or part of the given `byte` array to the `BLOB` value that this `Blob` object represents and returns the number of bytes written.
void	truncate(long len) Truncates the `BLOB` value that this `Blob` object represents to be `len` bytes in length.

Constructor Detail

jdbcBlob

public jdbcBlob(byte[] data)

Constructs a new jdbcBlob instance wrapping the given octet sequence.

This constructor is used internally to retrieve result set values as Blob objects, yet it must be public to allow access from other packages. As such (in the interest of efficiency) this object maintains a reference to the given octet sequence rather than making a copy; special care should be taken by extenal clients never to use this constructor with a byte array object that may later be modified extenally.

Parameters: data the octet sequence representing the Blob value

Throws: SQLException if the argument is null

Method Detail

getBinaryStream

public InputStream getBinaryStream()

Retrieves the BLOB value designated by this Blob instance as a stream.

Returns: a stream containing the BLOB data

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.2, HSQLDB 1.7.2

See Also: jdbcBlob

getBytes

public byte[] getBytes(long pos, int length)

Retrieves all or part of the BLOB value that this Blob object represents, as an array of bytes. This byte array contains up to length consecutive bytes starting at position pos.

HSQLDB-Specific Information:

The official specification above is ambiguous in that it does not precisely indicate the policy to be observed when pos > this.length() - length. One policy would be to retrieve the octets from pos to this.length(). Another would be to throw an exception. HSQLDB observes the later policy.

Parameters: pos the ordinal position of the first byte in the BLOB value to be extracted; the first byte is at position 1 length the number of consecutive bytes to be copied

Returns: a byte array containing up to length consecutive bytes from the BLOB value designated by this Blob object, starting with the byte at position pos

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.2, HSQLDB 1.7.2

See Also: jdbcBlob

length

public long length()

Returns the number of bytes in the BLOB value designated by this Blob object.

Returns: length of the BLOB in bytes

Throws: SQLException if there is an error accessing the length of the BLOB

Since: JDK 1.2, HSQLDB 1.7.2

position

public long position(byte[] pattern, long start)

Retrieves the byte position at which the specified byte array pattern begins within the BLOB value that this Blob object represents. The search for pattern begins at position start.

Parameters: pattern the byte array for which to search start the position at which to begin searching; the first position is 1

Returns: the position at which the pattern appears, else -1

Throws: SQLException if there is an error accessing the BLOB

Since: JDK 1.2, HSQLDB 1.7.2

position

public long position(Blob pattern, long start)

Retrieves the byte position in the BLOB value designated by this Blob object at which pattern begins. The search begins at position start.

Parameters: pattern the Blob object designating the BLOB value for which to search start the position in the BLOB value at which to begin searching; the first position is 1

Returns: the position at which the pattern begins, else -1

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.2, HSQLDB 1.7.2

setBinaryStream

public OutputStream setBinaryStream(long pos)

Retrieves a stream that can be used to write to the BLOB value that this Blob object represents. The stream begins at position pos.

HSQLDB-Specific Information:

HSQLDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

Parameters: pos the position in the BLOB value at which to start writing

Returns: a java.io.OutputStream object to which data can be written

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.4, HSQLDB 1.7.2

See Also: jdbcBlob

setBytes

public int setBytes(long pos, byte[] bytes)

Writes the given array of bytes to the BLOB value that this Blob object represents, starting at position pos, and returns the number of bytes written.

HSQLDB-Specific Information:

HSLQDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

Parameters: pos the position in the BLOB object at which to start writing bytes the array of bytes to be written to the BLOB value that this Blob object represents

Returns: the number of bytes written

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.4, HSQLDB 1.7.2

See Also: jdbcBlob

setBytes

public int setBytes(long pos, byte[] bytes, int offset, int len)

Writes all or part of the given byte array to the BLOB value that this Blob object represents and returns the number of bytes written. Writing starts at position pos in the BLOB value; len bytes from the given byte array are written.

HSQLDB-Specific Information:

HSLQDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

Parameters: pos the position in the BLOB object at which to start writing bytes the array of bytes to be written to this BLOB object offset the offset into the array bytes at which to start reading the bytes to be set len the number of bytes to be written to the BLOB value from the array of bytes bytes

Returns: the number of bytes written

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.4, HSQLDB 1.7.2

See Also: jdbcBlob

truncate

public void truncate(long len)

Truncates the BLOB value that this Blob object represents to be len bytes in length.

HSQLDB-Specific Information:

This operation affects only the client-side value; it has no effect upon the value as it is stored in the database.

Parameters: len the length, in bytes, to which the BLOB value that this Blob object represents should be truncated

Throws: SQLException if there is an error accessing the BLOB value

Since: JDK 1.4, HSQLDB 1.7.2