org.hsqldb.jdbc
Class jdbcBlob

java.lang.Object
  extended byorg.hsqldb.jdbc.jdbcBlob
All Implemented Interfaces:
java.sql.Blob

public class jdbcBlob
extends java.lang.Object
implements java.sql.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.

HSQLDB-Specific Information:

Including 1.7.2, 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
 java.io.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(java.sql.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.
 java.io.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.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

jdbcBlob

public jdbcBlob(byte[] data)
         throws java.sql.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
Throws:
java.sql.SQLException - if the argument is null
Method Detail

length

public long length()
            throws java.sql.SQLException
Returns the number of bytes in the BLOB value designated by this Blob object.

Specified by:
length in interface java.sql.Blob
Returns:
length of the BLOB in bytes
Throws:
java.sql.SQLException - if there is an error accessing the length of the BLOB
Since:
JDK 1.2, HSQLDB 1.7.2

getBytes

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

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.

Specified by:
getBytes in interface java.sql.Blob
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:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.2, HSQLDB 1.7.2
See Also:
setBytes(long, byte[])

getBinaryStream

public java.io.InputStream getBinaryStream()
                                    throws java.sql.SQLException
Retrieves the BLOB value designated by this Blob instance as a stream.

Specified by:
getBinaryStream in interface java.sql.Blob
Returns:
a stream containing the BLOB data
Throws:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.2, HSQLDB 1.7.2
See Also:
setBinaryStream(long)

position

public long position(byte[] pattern,
                     long start)
              throws java.sql.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.

Specified by:
position in interface java.sql.Blob
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:
java.sql.SQLException - if there is an error accessing the BLOB
Since:
JDK 1.2, HSQLDB 1.7.2

position

public long position(java.sql.Blob pattern,
                     long start)
              throws java.sql.SQLException
Retrieves the byte position in the BLOB value designated by this Blob object at which pattern begins. The search begins at position start.

Specified by:
position in interface java.sql.Blob
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:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.2, HSQLDB 1.7.2

setBytes

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

HSQLDB-Specific Information:

HSLQDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

Specified by:
setBytes in interface java.sql.Blob
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:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.4, HSQLDB 1.7.2
See Also:
getBytes(long, int)

setBytes

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

HSQLDB-Specific Information:

HSLQDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

Specified by:
setBytes in interface java.sql.Blob
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:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.4, HSQLDB 1.7.2
See Also:
getBytes(long, int)

setBinaryStream

public java.io.OutputStream setBinaryStream(long pos)
                                     throws java.sql.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.

HSQLDB-Specific Information:

HSQLDB 1.7.2 does not support this feature.

Calling this method always throws an SQLException.

Specified by:
setBinaryStream in interface java.sql.Blob
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:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.4, HSQLDB 1.7.2
See Also:
getBinaryStream()

truncate

public void truncate(long len)
              throws java.sql.SQLException
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.

Specified by:
truncate in interface java.sql.Blob
Parameters:
len - the length, in bytes, to which the BLOB value that this Blob object represents should be truncated
Throws:
java.sql.SQLException - if there is an error accessing the BLOB value
Since:
JDK 1.4, HSQLDB 1.7.2


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