程序包 java.sql

接口 Blob

所有已知实现类:

Blob

public interface Blob

The representation (mapping) in the Java™ programming language of an SQL BLOB value. An SQL BLOB is a built-in type that stores a Binary Large Object as a column value in a row of a database table. By default drivers implement Blob using an SQL locator(BLOB), which means that a Blob object contains a logical pointer to the SQL BLOB data rather than the data itself. A Blob object is valid for the duration of the transaction in which is was created.

Methods in the interfaces ResultSet, CallableStatement, and PreparedStatement, such as getBlob and setBlob allow a programmer to access an SQL BLOB value. The Blob interface 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 a pattern of bytes within a BLOB value. In addition, this interface has methods for updating a BLOB value.

All methods on the Blob interface must be fully implemented if the JDBC driver supports the data type.

从以下版本开始:

1.2

方法概要

限定符和类型	方法	说明
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.
long	length()	Returns the number of bytes in the BLOB value designated by this Blob object.
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.
long	position(Blob pattern, long start)	Retrieves the byte position in the BLOB value designated by this Blob object at which pattern begins.
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.

方法详细资料

length

long length()
     throws SQLException

Returns the number of bytes in the BLOB value designated by this Blob object.

返回:

length of the BLOB in bytes

抛出:

SQLException - if there is an error accessing the length of the BLOB

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

从以下版本开始:

1.2

getBytes

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.

参数:

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

返回:

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

抛出:

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

从以下版本开始:

1.2

另请参阅:

setBytes(long, byte[])

getBinaryStream

InputStream getBinaryStream()
                     throws SQLException

Retrieves the BLOB value designated by this Blob instance as a stream.

返回:

a stream containing the BLOB data

抛出:

SQLException - if there is an error accessing the BLOB value

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

从以下版本开始:

1.2

另请参阅:

setBinaryStream(long)

position

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.

参数:

pattern - the byte array for which to search

start - the position at which to begin searching; the first position is 1

返回:

the position at which the pattern appears, else -1

抛出:

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

从以下版本开始:

1.2

position

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.

参数:

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

返回:

the position at which the pattern begins, else -1

抛出:

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

从以下版本开始:

1.2

setBytes

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.

参数:

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

返回:

the number of bytes written

抛出:

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

从以下版本开始:

1.4

另请参阅:

getBytes(long, int)

setBytes

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.

参数:

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

返回:

the number of bytes written

抛出:

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

从以下版本开始:

1.4

另请参阅:

getBytes(long, int)

setBinaryStream

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.

参数:

pos - the position in the BLOB value at which to start writing; the first position is 1

返回:

a java.io.OutputStream object to which data can be written

抛出:

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

从以下版本开始:

1.4

另请参阅:

getBinaryStream()

truncate

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.

参数:

len - the length, in bytes, to which the BLOB value that this Blob object represents should be truncated

抛出:

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

从以下版本开始:

1.4

free

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.

抛出:

SQLException - if an error occurs releasing the Blob's resources

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

从以下版本开始:

1.6

getBinaryStream

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.

参数:

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

返回:

InputStream through which the partial Blob value can be read.

抛出:

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

从以下版本开始:

1.6