Class EmbedBlob
Supports
- JSR169 - no subsetting for java.sql.Blob
- JDBC 2.0
- JDBC 3.0 - no new dependencies on new JDBC 3.0 or JDK 1.4 classes, new update methods can safely be added into implementation.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate LOBStreamControl
private boolean
private int
Locator value for this Blob, used as a handle by the client driver to map operations to the correct Blob on the server side.private boolean
Tells whether the Blob has been materialized or not.private PositionedStoreStream
The underlying positionable store stream, if any.private long
Length of the stream representing the Blob.private final int
Position offset for the stream representing the Blob, if any.Fields inherited from class org.apache.derby.impl.jdbc.ConnectionChild
factory, localConn
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Constructor Summary
ConstructorsModifierConstructorDescription(package private)
EmbedBlob
(byte[] blobBytes, EmbedConnection con) This constructor is used to create a empty Blob object.protected
EmbedBlob
(DataValueDescriptor dvd, EmbedConnection con) -
Method Summary
Modifier and TypeMethodDescriptionprivate boolean
checkMatch
(byte[] pattern, long pos) Checks if the pattern (starting from the second byte) appears inside the Blob content.private boolean
checkMatch
(Blob pattern, long pos) Checks if the pattern (starting from the second byte) appears inside the Blob content.private void
protected void
finalize()
void
free()
This method frees theBlob
object and releases the resources that it holds.Retrieves theBLOB
designated by thisBlob
instance as a stream.getBinaryStream
(long pos, long length) Returns anInputStream
object that contains a partialBlob
value, starting with the byte specified by pos, which is length bytes in length.byte[]
getBytes
(long startPos, int length) Returns as an array of bytes part or all of theBLOB
value that thisBlob
object designates.int
Return locator for this lob.private SQLException
private int
handleStreamValue
(InputStream dvdStream, EmbedConnection con) Constructs a Blob object on top of a stream.(package private) boolean
Returns if blob data is stored locally (using LOBStreamControl).long
length()
Returns the number of bytes in theBLOB
value designated by thisBlob
object.long
position
(byte[] pattern, long start) Determines the byte position at which the specified bytepattern
begins within theBLOB
value that thisBlob
object represents.long
Determines the byte position in theBLOB
value designated by thisBlob
object at whichpattern
begins.private int
read
(long pos) Reads one byte from the Blob at the specified position.setBinaryStream
(long pos) JDBC 3.0 Retrieves a stream that can be used to write to the BLOB value that this Blob object represents.private long
setBlobPosition
(long logicalPos) Sets the position of the Blob tologicalPos
, where position 0 is the beginning of the Blob content.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 array of byte array to the BLOB value that this Blob object represents and returns the number of bytes written.void
truncate
(long len) JDBC 3.0 Truncates the BLOB value that this Blob object represents to be len bytes in length.Methods inherited from class org.apache.derby.impl.jdbc.ConnectionChild
commitIfAutoCommit, commitIfNeeded, getCal, getConnectionSynchronization, getEmbedConnection, getLanguageConnectionContext, getLCC, handleException, needCommit, newSQLException, restoreContextStack, restoreIntrFlagIfSeen, setupContextStack
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Field Details
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materialized
private boolean materializedTells whether the Blob has been materialized or not.Materialization happens when the Blob is updated by the user. A materialized Blob is represented either in memory or in a temporary file on disk, depending on size.
A Blob that has not been materialized is represented by a stream into the Derby store, and is read-only.
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myStream
The underlying positionable store stream, if any.If
materialized
istrue
, the stream isnull
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locator
private int locatorLocator value for this Blob, used as a handle by the client driver to map operations to the correct Blob on the server side.- See Also:
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streamLength
private long streamLengthLength of the stream representing the Blob.Set to -1 when the stream has been
materialized
or the length of the stream is not currently known. -
streamPositionOffset
private final int streamPositionOffsetPosition offset for the stream representing the Blob, if any.This offset accounts for the bytes encoding the stream length at the head of the stream. Data byte
pos
is atpos + streamPositionOffset
in the underlying stream. Set toInteger.MIN_VALUE
if the Blob isn't represented by a store stream. -
isValid
private boolean isValid -
control
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Constructor Details
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EmbedBlob
EmbedBlob(byte[] blobBytes, EmbedConnection con) throws SQLException This constructor is used to create a empty Blob object. It is used by the Connection interface method createBlob().- Parameters:
blobBytes
- A byte array containing the data to be stores in the Blob.con
- The EmbedConnection object associated with this Blob object.- Throws:
SQLException
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EmbedBlob
protected EmbedBlob(DataValueDescriptor dvd, EmbedConnection con) throws StandardException, SQLException - Throws:
StandardException
SQLException
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Method Details
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handleStreamValue
private int handleStreamValue(InputStream dvdStream, EmbedConnection con) throws StandardException, SQLException Constructs a Blob object on top of a stream.- Parameters:
dvdStream
- the source streamcon
- the connection owning the Blob- Returns:
- The offset into the stream where the user data begins (used if resetting the stream).
- Throws:
StandardException
- if accessing the stream fails, or if writing data to temporary storage failsSQLException
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setBlobPosition
Sets the position of the Blob tologicalPos
, where position 0 is the beginning of the Blob content.The position is only guaranteed to be valid from the time this method is invoked until the synchronization monitor is released, or until the next invokation of this method.
The position is logical in the sense that it specifies the requested position in the Blob content. This position might be at a different position in the underlying representation, for instance the Derby store stream prepends the Blob content with a length field.
- Parameters:
logicalPos
- requested Blob position, 0-based- Returns:
- The new position, which will be equal to the requested position.
- Throws:
IOException
- if reading/accessing the Blob failsStandardException
- throws BLOB_POSITION_TOO_LARGE if the requested position is larger than the Blob length, throws other SQL states if resetting the stream fails
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read
Reads one byte from the Blob at the specified position.Depending on the representation, this might result in a read from a byte array, a temporary file on disk or from a Derby store stream.
- Returns:
- the byte at the current position, or -1 if end of file has been reached
- Throws:
IOException
- if reading from the underlying data representation failsStandardException
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length
Returns the number of bytes in theBLOB
value designated by thisBlob
object.- Specified by:
length
in interfaceBlob
- Returns:
- length of the
BLOB
in bytes - Throws:
SQLException
- if there is an error accessing the length of theBLOB
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getBytes
Returns as an array of bytes part or all of theBLOB
value that thisBlob
object designates. The byte array contains up tolength
consecutive bytes starting at positionstartPos
. The starting position must be between 1 and the length of the BLOB plus 1. This allows for zero-length BLOB values, from which only zero-length byte arrays can be returned. If a larger length is requested than there are bytes available, characters from the start position to the end of the BLOB are returned.- Specified by:
getBytes
in interfaceBlob
- Parameters:
startPos
- the ordinal position of the first byte in theBLOB
value to be extracted; the first byte is at position 1length
- is the number of consecutive bytes to be copied- Returns:
- a byte array containing up to
length
consecutive bytes from theBLOB
value designated by thisBlob
object, starting with the byte at positionstartPos
. - Throws:
SQLException
- if there is an error accessing theBLOB
NOTE: If the starting position is the length of the BLOB plus 1, zero bytess are returned regardless of the length requested.
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getBinaryStream
Retrieves theBLOB
designated by thisBlob
instance as a stream.- Specified by:
getBinaryStream
in interfaceBlob
- Returns:
- a stream containing the
BLOB
data - Throws:
SQLException
- if there is an error accessing theBLOB
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position
Determines the byte position at which the specified bytepattern
begins within theBLOB
value that thisBlob
object represents. The search forpattern
. begins at positionstart
- Specified by:
position
in interfaceBlob
- Parameters:
pattern
- the byte array for which to searchstart
- 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 theBLOB
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checkMatch
Checks if the pattern (starting from the second byte) appears inside the Blob content.At this point, the first byte of the pattern must already have been matched, and
pos
must be pointing at the second byte to compare.- Parameters:
pattern
- the byte array to search for, passed in by the userpos
- the position in the Blob content to start searching from- Returns:
true
if a match is found,false
if not.- Throws:
IOException
StandardException
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position
Determines the byte position in theBLOB
value designated by thisBlob
object at whichpattern
begins. The search begins at positionstart
.- Specified by:
position
in interfaceBlob
- Parameters:
pattern
- theBlob
object designating theBLOB
value for which to searchstart
- the position in theBLOB
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 theBLOB
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checkMatch
Checks if the pattern (starting from the second byte) appears inside the Blob content.- Parameters:
pattern
- the Blob to search for, passed in by the userpos
- the position in the Blob (this) content to start searching- Returns:
true
if a match is found,false
if not.- Throws:
IOException
StandardException
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handleMyExceptions
- Throws:
SQLException
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finalize
protected void finalize() -
setBytes
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.- Specified by:
setBytes
in interfaceBlob
- Parameters:
pos
- the position in the BLOB object at which to start writingbytes
- the array of bytes to be written to the BLOB value that this Blob object represents- Returns:
- The number of bytes written to the BLOB.
- Throws:
SQLException
- if writing the bytes to the BLOB fails- Since:
- 1.4
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setBytes
Writes all or part of the given array of 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.- Specified by:
setBytes
in interfaceBlob
- Parameters:
pos
- the position in the BLOB object at which to start writingbytes
- the array of bytes to be written to the BLOB value that this Blob object representsoffset
- the offset into the byte array at which to start reading the bytes to be writtenlen
- the number of bytes to be written to the BLOB value from the array of bytes bytes- Returns:
- The number of bytes written to the BLOB.
- Throws:
SQLException
- if writing the bytes to the BLOB failsIndexOutOfBoundsException
- iflen
is larger thanbytes.length - offset
- Since:
- 1.4
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setBinaryStream
JDBC 3.0 Retrieves a stream that can be used to write to the BLOB value that this Blob object represents. The stream begins at position pos.- Specified by:
setBinaryStream
in interfaceBlob
- Parameters:
pos
- - the position in the BLOB object at which to start writing- Returns:
- a java.io.OutputStream object to which data can be written
- Throws:
SQLException
- Feature not implemented for now.
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truncate
JDBC 3.0 Truncates the BLOB value that this Blob object represents to be len bytes in length.- Specified by:
truncate
in interfaceBlob
- Parameters:
len
- - the length, in bytes, to which the BLOB value that this Blob object represents should be truncated- Throws:
SQLException
- Feature not implemented for now.
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free
This method frees theBlob
object and releases the resources that it holds. The object is invalid once thefree
method is called. Iffree
is called multiple times, the subsequent calls tofree
are treated as a no-op.- Specified by:
free
in interfaceBlob
- Specified by:
free
in interfaceEngineLOB
- Throws:
SQLException
- if an error occurs releasing the Blob's resources
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getBinaryStream
Returns anInputStream
object that contains a partialBlob
value, starting with the byte specified by pos, which is length bytes in length.- Specified by:
getBinaryStream
in interfaceBlob
- Parameters:
pos
- the offset to the first byte of the partial value to be retrieved. The first byte in theBlob
is at position 1length
- the length in bytes of the partial value to be retrieved- Returns:
- through which the partial
Blob
value can be read. - Throws:
SQLException
- if pos is less than 1 or if pos is greater than the number of bytes in theBlob
or ifpos + length
is greater thanBlob.length() +1
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checkValidity
- Throws:
SQLException
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isMaterialized
boolean isMaterialized()Returns if blob data is stored locally (using LOBStreamControl).- Returns:
- true if materialized else false
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getLocator
public int getLocator()Return locator for this lob.- Specified by:
getLocator
in interfaceEngineLOB
- Returns:
- The locator identifying this lob.
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