public class JDBCBlobFile
extends java.lang.Object
implements java.sql.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 java.lang.String |
TEMP_FILE_PREFIX |
static java.lang.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(java.io.File file)
Convenience constructor; equivalent to JDBCBlobFile(file, false);
|
JDBCBlobFile(java.io.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. |
java.io.InputStream |
getBinaryStream()
Retrieves the
BLOB value designated by this
Blob instance as a stream. |
java.io.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. |
java.io.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(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 |
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 java.lang.String TEMP_FILE_PREFIX
public static final java.lang.String TEMP_FILE_SUFFIX
public JDBCBlobFile() throws java.sql.SQLException
java.sql.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 java.sql.SQLException
deleteOnFree
- Assigns whether an attempt to delete the backing file
is to be made in response to invocation of free()
.java.sql.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(java.io.File file) throws java.sql.SQLException
file
- used to back this BLOB instance.java.sql.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(java.io.File file, boolean deleteOnFree) throws java.sql.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()
.java.sql.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 java.sql.SQLException
BLOB
value
designated by this Blob
object.length
in interface java.sql.Blob
BLOB
in bytesjava.sql.SQLException
- if there is an error accessing the
length of the BLOB
java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic byte[] getBytes(long pos, int length) throws java.sql.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 java.sql.Blob
pos
- 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 pos
java.sql.SQLException
- if there is an error accessing the
BLOB
value; if pos is less than 1 or length is
less than 0java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodsetBytes(long, byte[])
public java.io.InputStream getBinaryStream() throws java.sql.SQLException
BLOB
value designated by this
Blob
instance as a stream.getBinaryStream
in interface java.sql.Blob
BLOB
datajava.sql.SQLException
- if there is an error accessing the
BLOB
valuejava.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodsetBinaryStream(long)
public long position(byte[] pattern, long start) throws java.sql.SQLException
pattern
begins within the BLOB
value that this Blob
object represents. The
search for pattern
begins at position
start
.position
in interface java.sql.Blob
pattern
- the byte array for which to searchstart
- the position at which to begin searching; the
first position is 1java.sql.SQLException
- if there is an error accessing the
BLOB
or if start is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic long position(java.sql.Blob pattern, long start) throws java.sql.SQLException
BLOB
value
designated by this Blob
object at which
pattern
begins. The search begins at position
start
.position
in interface java.sql.Blob
pattern
- 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 1java.sql.SQLException
- if there is an error accessing the
BLOB
value or if start is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic int setBytes(long pos, byte[] bytes) throws java.sql.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 java.sql.Blob
pos
- 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 representsjava.sql.SQLException
- if there is an error accessing the
BLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodgetBytes(long, int)
public int setBytes(long pos, byte[] bytes, int offset, int len) throws java.sql.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 java.sql.Blob
pos
- 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 bytes
java.sql.SQLException
- if there is an error accessing the
BLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodgetBytes(long, int)
public java.io.OutputStream setBinaryStream(long pos) throws java.sql.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 java.sql.Blob
pos
- the position in the BLOB
value at which
to start writing; the first position is 1java.io.OutputStream
object to which data can
be writtenjava.sql.SQLException
- if there is an error accessing the
BLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodgetBinaryStream()
public void truncate(long len) throws java.sql.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 java.sql.Blob
len
- the length, in bytes, to which the BLOB
value
that this Blob
object represents should be truncatedjava.sql.SQLException
- if there is an error accessing the
BLOB
value or if len is less than 0java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic void free() throws java.sql.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 java.sql.Blob
java.sql.SQLException
- if an error occurs releasing
the Blob's resourcesjava.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodsetDeleteOnFree(boolean)
,
isDeleteOnFree()
public java.io.InputStream getBinaryStream(long pos, long length) throws java.sql.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 java.sql.Blob
pos
- 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.java.sql.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 Blob
java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic java.io.File getFile()
public boolean isDeleteOnFree()
free()
.public void setDeleteOnFree(boolean deleteOnFree)
free()
.deleteOnFree
- the new value to assignCopyright �� 2001 - 2017 HSQL Development Group.