org.hsqldb.jdbc

Class jdbcBlob

Implemented Interfaces:
Blob

public class jdbcBlob
extends java.lang.Object
implements Blob

The representation (mapping) in the JavaTM 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.

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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.

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Authors:
james house jhouse@part.net
boucherb@users
Since:
JDK 1.2, HSQLDB 1.7.2

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(Blob pattern, long start)
Retrieves the byte position in the BLOB value designated by this Blob object at which pattern begins.
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.
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 Details

jdbcBlob

public jdbcBlob(byte[] data)
            throws SQLException
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

Method Details

getBinaryStream

public InputStream getBinaryStream()
            throws SQLException
Retrieves the BLOB value designated by this Blob instance as a stream.
Returns:
a stream containing the BLOB data
Since:
JDK 1.2, HSQLDB 1.7.2

getBytes

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

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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
Since:
JDK 1.2, HSQLDB 1.7.2
See Also:
setBytes

length

public long length()
            throws SQLException
Returns the number of bytes in the BLOB value designated by this Blob object.
Returns:
length of the BLOB in bytes
Since:
JDK 1.2, HSQLDB 1.7.2

position

public long position(Blob pattern,
                     long start)
            throws SQLException
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
Since:
JDK 1.2, HSQLDB 1.7.2

position

public long position(byte[] pattern,
                     long start)
            throws SQLException
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
Since:
JDK 1.2, HSQLDB 1.7.2

setBinaryStream

public OutputStream setBinaryStream(long pos)
            throws SQLException
Retrieves a stream that can be used to write to the BLOB value that this Blob object represents. The stream begins at position pos.

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HSQLDB-Specific Information:

HSQLDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

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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
Since:
JDK 1.4, HSQLDB 1.7.2

setBytes

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

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HSQLDB-Specific Information:

HSLQDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

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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
Since:
JDK 1.4, HSQLDB 1.7.2

setBytes

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

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HSQLDB-Specific Information:

HSLQDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

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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
Since:
JDK 1.4, HSQLDB 1.7.2

truncate

public void truncate(long len)
            throws SQLException
Truncates the BLOB value that this Blob object represents to be len bytes in length. <!-- start release-specific documentation -->

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.

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Parameters:
len - the length, in bytes, to which the BLOB value that this Blob object represents should be truncated
Since:
JDK 1.4, HSQLDB 1.7.2

Copyright B) 2001 - 2005 HSQL Development Group. All Rights Reserved.