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org.hsqldb.jdbc
Class JDBCBlobFile

java.lang.Object
  extended by org.hsqldb.jdbc.JDBCBlobFile
All Implemented Interfaces:
Blob
public class JDBCBlobFile
extends Object
implements Blob

HSQLDB-Specific Information:

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.

Since:
HSQLDB 2.1
Author:
boucherb@users

Field Summary
static String TEMP_FILE_PREFIX
           
static String TEMP_FILE_SUFFIX
           
 
Constructor Summary
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.
 
Method Summary
 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.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

TEMP_FILE_PREFIX

public static final String TEMP_FILE_PREFIX
See Also:
Constant Field Values

TEMP_FILE_SUFFIX

public static final String TEMP_FILE_SUFFIX
See Also:
Constant Field Values
Constructor Detail

JDBCBlobFile

public JDBCBlobFile()
             throws SQLException
Convenience constructor; equivalent to JDBCBlobFile(true);

Throws:
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.

JDBCBlobFile

public JDBCBlobFile(boolean deleteOnFree)
             throws SQLException
Constructs a new instance backed by a File object created in response to invoking File.createTempFile(TEMP_FILE_PREFIX,TEMP_FILE_SUFFIX)

Parameters:
deleteOnFree - Assigns whether an attempt to delete the backing file is to be made in response to invocation of free().
Throws:
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.

JDBCBlobFile

public JDBCBlobFile(File file)
             throws SQLException
Convenience constructor; equivalent to JDBCBlobFile(file, false);

Parameters:
file - used to back this BLOB instance.
Throws:
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 file

JDBCBlobFile

public JDBCBlobFile(File file,
                    boolean deleteOnFree)
             throws SQLException
Constructs a new instance backed by the given File object.

Parameters:
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().
Throws:
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 file
Method Detail

length

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

Specified by:
length in interface Blob
Returns:
length of the BLOB in bytes
Throws:
SQLException - if there is an error accessing the length of the BLOB
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.2

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.

Specified by:
getBytes in interface 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; the value for length must be 0 or greater
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:
SQLException - if there is an error accessing the BLOB value; if pos is less than 1 or length is less than 0
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.2
See Also:
setBytes(long, byte[])

getBinaryStream

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

Specified by:
getBinaryStream in interface Blob
Returns:
a stream containing the BLOB data
Throws:
SQLException - if there is an error accessing the BLOB value
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.2
See Also:
setBinaryStream(long)

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.

Specified by:
position in interface 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:
SQLException - if there is an error accessing the BLOB or if start is less than 1
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.2

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.

Specified by:
position in interface 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:
SQLException - if there is an error accessing the BLOB value or if start is less than 1
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.2

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. 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.

HSQLDB-Specific Information:

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 updateable ResultSet.

Specified by:
setBytes in interface Blob
Parameters:
pos - the position in the BLOB object at which to start writing; the first position is 1
bytes - the array of bytes to be written to the BLOB value that this Blob object represents
Returns:
the number of bytes written
Throws:
SQLException - if there is an error accessing the BLOB value or if pos is less than 1
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.4
See Also:
getBytes(long, int)

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. 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.

HSQLDB-Specific Information:

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 updateable ResultSet.

Specified by:
setBytes in interface Blob
Parameters:
pos - the position in the BLOB object at which to start writing; the first position is 1
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:
SQLException - if there is an error accessing the BLOB value or if pos is less than 1
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.4
See Also:
getBytes(long, int)

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. 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.

HSQLDB-Specific Information:

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.

Specified by:
setBinaryStream in interface Blob
Parameters:
pos - the position in the BLOB value at which to start writing; the first position is 1
Returns:
a java.io.OutputStream object to which data can be written
Throws:
SQLException - if there is an error accessing the BLOB value or if pos is less than 1
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.4
See Also:
getBinaryStream()

truncate

public void truncate(long len)
              throws SQLException
Truncates the 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.

HSQLDB-Specific Information:

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 updateable ResultSet.

Specified by:
truncate in interface Blob
Parameters:
len - the length, in bytes, to which the BLOB value that this Blob object represents should be truncated
Throws:
SQLException - if there is an error accessing the BLOB value or if len is less than 0
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.4

free

public void free()
          throws SQLException
This method frees the 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.

HSQLDB-Specific Information:

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.

Specified by:
free in interface Blob
Throws:
SQLException - if an error occurs releasing the Blob's resources
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.6
See Also:
setDeleteOnFree(boolean), isDeleteOnFree()

getBinaryStream

public InputStream getBinaryStream(long pos,
                                   long length)
                            throws SQLException
Returns an InputStream object that contains a partial Blob value, starting with the byte specified by pos, which is length bytes in length.

Specified by:
getBinaryStream in interface Blob
Parameters:
pos - the offset to the first byte of the partial value to be retrieved. The first byte in the Blob is at position 1
length - the length in bytes of the partial value to be retrieved
Returns:
InputStream 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 the Blob or if pos + length is greater than the number of bytes in the Blob
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
JDK 1.6

getFile

public File getFile()
Retrieves the canonical File object denoting the file that backs this BLOB.

Returns:
the file that backs this BLOB.

isDeleteOnFree

public boolean isDeleteOnFree()
Retrieves whether an attempt to delete the backing file is made in response to invocation of free().

Returns:
true if backing file deletion is attempted; otherwise false.

setDeleteOnFree

public void setDeleteOnFree(boolean deleteOnFree)
Assigns whether an attempt to delete the backing file is made in response to invocation of free().

Parameters:
deleteOnFree - the new value to assign
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