public class JDBCBlobFile extends Object implements Blob
Starting with 2.1, in addition to HSQLDB driver support for both client-side in-memory and remote SQL CLOB data implementations, this class is provided to expose efficient, relatively high-performance BLOB operations over client accessible files.
Design Notes
Although it is possible to implement a transactional version of this class, the present implementation directly propagates changes to the underlying file such that changes become visible as soon as they are either implicitly or explicitly flushed to disk.
| Modifier and Type | Field and Description |
|---|---|
static String |
TEMP_FILE_PREFIX |
static String |
TEMP_FILE_SUFFIX |
| Constructor and Description |
|---|
JDBCBlobFile()
Convenience constructor; equivalent to JDBCBlobFile(true);
|
JDBCBlobFile(boolean deleteOnFree)
Constructs a new instance backed by a File object created in response
to invoking File.createTempFile(TEMP_FILE_PREFIX,TEMP_FILE_SUFFIX)
|
JDBCBlobFile(File file)
Convenience constructor; equivalent to JDBCBlobFile(file, false);
|
JDBCBlobFile(File file,
boolean deleteOnFree)
Constructs a new instance backed by the given File object.
|
| Modifier and Type | Method and Description |
|---|---|
void |
free()
This method frees the
Blob object and releases the resources that
it holds. |
InputStream |
getBinaryStream()
Retrieves the
BLOB value designated by this
Blob instance as a stream. |
InputStream |
getBinaryStream(long pos,
long length)
Returns an
InputStream object that contains a partial Blob value,
starting with the byte specified by pos, which is length bytes in length. |
byte[] |
getBytes(long pos,
int length)
Retrieves all or part of the
BLOB
value that this Blob object represents, as an array of
bytes. |
File |
getFile()
Retrieves the canonical File object denoting the file that
backs this BLOB.
|
boolean |
isDeleteOnFree()
Retrieves whether an attempt to delete the backing file
is made in response to invocation of
free(). |
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 |
setDeleteOnFree(boolean deleteOnFree)
Assigns whether an attempt to delete the backing file
is made in response to invocation of
free(). |
void |
truncate(long len)
Truncates the
BLOB value that this Blob
object represents to be len bytes in length. |
public static final String TEMP_FILE_PREFIX
public static final String TEMP_FILE_SUFFIX
public JDBCBlobFile()
throws SQLException
SQLException - If a file could not be created or if a security
manager exists and its SecurityManager.checkWrite(java.lang.String)
method does not allow a file to be created.public JDBCBlobFile(boolean deleteOnFree)
throws SQLException
deleteOnFree - Assigns whether an attempt to delete the backing file
is to be made in response to invocation of free().SQLException - If a file could not be created or if a security
manager exists and its SecurityManager.checkWrite(java.lang.String)
method does not allow a file to be created.public JDBCBlobFile(File file) throws SQLException
file - used to back this BLOB instance.SQLException - If an I/O error occurs, which is possible because
the construction of the canonical pathname may require file system
queries; if a required system property value cannot be accessed,
or if a security manager exists and its SecurityManager.checkRead(java.io.FileDescriptor) method denies
read access to the filepublic JDBCBlobFile(File file, boolean deleteOnFree) throws SQLException
file - used to back this BLOB instance.deleteOnFree - Assigns whether an attempt to delete the backing file
is to be made in response to invocation of free().SQLException - If an I/O error occurs, which is possible because
the construction of the canonical pathname may require file system
queries; if a required system property value cannot be accessed,
or if a security manager exists and its SecurityManager.checkRead(java.io.FileDescriptor) method denies
read access to the filepublic long length()
throws SQLException
BLOB value
designated by this Blob object.length in interface BlobBLOB in bytesSQLException - if there is an error accessing the
length of the BLOBSQLFeatureNotSupportedException - if the JDBC driver does not support
this methodpublic byte[] getBytes(long pos,
int length)
throws SQLException
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.getBytes in interface Blobpos - the ordinal position of the first byte in the
BLOB value to be extracted; the first byte is at
position 1length - the number of consecutive bytes to be copied; the value
for length must be 0 or greaterlength
consecutive bytes from the BLOB value designated
by this Blob object, starting with the
byte at position posSQLException - if there is an error accessing the
BLOB value; if pos is less than 1 or length is
less than 0SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodsetBytes(long, byte[])public InputStream getBinaryStream() throws SQLException
BLOB value designated by this
Blob instance as a stream.getBinaryStream in interface BlobBLOB dataSQLException - if there is an error accessing the
BLOB valueSQLFeatureNotSupportedException - if the JDBC driver does not support
this methodsetBinaryStream(long)public long position(byte[] pattern,
long start)
throws SQLException
pattern begins within the BLOB
value that this Blob object represents. The
search for pattern begins at position
start.position in interface Blobpattern - the byte array for which to searchstart - the position at which to begin searching; the
first position is 1SQLException - if there is an error accessing the
BLOB or if start is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodpublic long position(Blob pattern, long start) throws SQLException
BLOB value
designated by this Blob object at which
pattern begins. The search begins at position
start.position in interface Blobpattern - the Blob object designating
the BLOB value for which to searchstart - the position in the BLOB value
at which to begin searching; the first position is 1SQLException - if there is an error accessing the
BLOB value or if start is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodpublic int setBytes(long pos,
byte[] bytes)
throws SQLException
BLOB value that
this Blob object represents, starting at position
pos, and returns the number of bytes written.
The array of bytes will overwrite the existing bytes
in the Blob object starting at the position
pos. If the end of the Blob value is reached
while writing the array of bytes, then the length of the Blob
value will be increased to accommodate the extra bytes.
Note: If the value specified for pos
is greater then the length+1 of the BLOB value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException while other drivers may support this
operation.
This operation affects only the content of the underlying file; it has no effect upon a value stored in a database. To propagate the updated Blob value to a database, it is required to supply the Blob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Blob instance to an updateXXX method of an updatable ResultSet.
setBytes in interface Blobpos - the position in the BLOB object at which
to start writing; the first position is 1bytes - the array of bytes to be written to the BLOB
value that this Blob object representsSQLException - if there is an error accessing the
BLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodgetBytes(long, int)public int setBytes(long pos,
byte[] bytes,
int offset,
int len)
throws SQLException
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.
The array of bytes will overwrite the existing bytes
in the Blob object starting at the position
pos. If the end of the Blob value is reached
while writing the array of bytes, then the length of the Blob
value will be increased to accommodate the extra bytes.
Note: If the value specified for pos
is greater then the length+1 of the BLOB value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException while other drivers may support this
operation.
This operation affects only the content of the underlying file; it has no effect upon a value stored in a database. To propagate the updated Blob value to a database, it is required to supply the Blob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Blob instance to an updateXXX method of an updatable ResultSet.
setBytes in interface Blobpos - the position in the BLOB object at which
to start writing; the first position is 1bytes - the array of bytes to be written to this BLOB
objectoffset - the offset into the array bytes at which
to start reading the bytes to be setlen - the number of bytes to be written to the BLOB
value from the array of bytes bytesSQLException - if there is an error accessing the
BLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodgetBytes(long, int)public OutputStream setBinaryStream(long pos) throws SQLException
BLOB
value that this Blob object represents. The stream begins
at position pos.
The bytes written to the stream will overwrite the existing bytes
in the Blob object starting at the position
pos. If the end of the Blob value is reached
while writing to the stream, then the length of the Blob
value will be increased to accommodate the extra bytes.
Note: If the value specified for pos
is greater then the length+1 of the BLOB value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException while other drivers may support this
operation.
Data written to the returned stream affects only the content of the underlying file; it has no effect upon a value stored in a database. To propagate the updated Blob value to a database, it is required to supply the Blob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Blob instance to an updateXXX method of an updateable ResultSet.
setBinaryStream in interface Blobpos - the position in the BLOB value at which
to start writing; the first position is 1java.io.OutputStream object to which data can
be writtenSQLException - if there is an error accessing the
BLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodgetBinaryStream()public void truncate(long len)
throws SQLException
BLOB value that this Blob
object represents to be len bytes in length.
Note: If the value specified for pos
is greater then the length+1 of the BLOB value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException while other drivers may support this
operation.
This operation affects only the length of the underlying file; it has no effect upon a value stored in a database. To propagate the truncated Blob value to a database, it is required to supply the Blob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Blob instance to an updateXXX method of an updatable ResultSet.
truncate in interface Bloblen - the length, in bytes, to which the BLOB value
that this Blob object represents should be truncatedSQLException - if there is an error accessing the
BLOB value or if len is less than 0SQLFeatureNotSupportedException - if the JDBC driver does not support
this methodpublic void free()
throws SQLException
Blob object and releases the resources that
it holds. The object is invalid once the free
method is called.
After free has been called, any attempt to invoke a
method other than free will result in a SQLException
being thrown. If free is called multiple times, the subsequent
calls to free are treated as a no-op.
This operation closes any input and/or output streams obtained
via getBinaryStream(), getBinaryStream(long, long) or
setBinaryStream(long).
Additionally, if the property isDeleteOnFree() is true, then
an attempt is made to delete the backing file.
free in interface BlobSQLException - if an error occurs releasing
the Blob's resourcesSQLFeatureNotSupportedException - if the JDBC driver does not support
this methodsetDeleteOnFree(boolean),
isDeleteOnFree()public InputStream getBinaryStream(long pos, long length) throws SQLException
InputStream object that contains a partial Blob value,
starting with the byte specified by pos, which is length bytes in length.getBinaryStream in interface Blobpos - the offset to the first byte of the partial value to be retrieved.
The first byte in the Blob is at position 1length - the length in bytes of the partial value to be retrievedInputStream through which the partial Blob value can be read.SQLException - if pos is less than 1 or if pos is greater than the number of bytes
in the Blob or if pos + length is greater than the number of bytes
in the BlobSQLFeatureNotSupportedException - if the JDBC driver does not support
this methodpublic File getFile()
public boolean isDeleteOnFree()
free().public void setDeleteOnFree(boolean deleteOnFree)
free().deleteOnFree - the new value to assignCopyright © 2001 - 2017 HSQL Development Group.