org.springframework.jdbc.support.lob
Interface LobHandler

All Known Implementing Classes:

DefaultLobHandler, OracleLobHandler

public interface LobHandler

Abstraction for handling large binary fields and large text fields in specific databases, no matter if represented as simple types or Large OBjects. Its main purpose is to isolate Oracle's peculiar handling of LOBs in OracleLobHandler; most other databases should work with DefaultLobHandler.

Provides accessor methods for BLOBs and CLOBs, and acts as factory for LobCreator instances, to be used as sessions for creating BLOBs or CLOBs. LobCreators are typically instantiated for each statement execution or for each transaction. They are not thread-safe because they might track allocated database resources to be able to free them after execution.

Most databases/drivers should be able to work with DefaultLobHandler, which simply delegates to JDBC's direct accessor methods, avoiding java.sql.Blob and java.sql.Clob completely. Unfortunately, Oracle just accepts Blob/Clob instances created via its own proprietary BLOB/CLOB API, and additionally doesn't accept large streams for PreparedStatement's corresponding setter methods. Therefore, you need to use OracleLobHandler there, which uses Oracle's BLOB/CLOB API for both all access.

Of course, you need to declare different field types for each database. In Oracle, any binary content needs to go into a BLOB, and all character content beyond 4000 bytes needs to go into a CLOB. In MySQL, there is no notion of a CLOB type but rather a LONGTEXT type that behaves like a VARCHAR. For complete portability, just use a LobHandler for fields that might typically require LOBs on some database because of their size (take Oracle's numbers as a guideline).

Since:

23.12.2003

Author:

Juergen Hoeller

See Also:

DefaultLobHandler, OracleLobHandler, ResultSet.getBytes(int), ResultSet.getBinaryStream(int), ResultSet.getString(int), ResultSet.getAsciiStream(int), ResultSet.getCharacterStream(int)

Method Summary

InputStream	getBlobAsBinaryStream(ResultSet rs, int columnIndex) Retrieve the given column as binary stream from the given ResultSet.
byte[]	getBlobAsBytes(ResultSet rs, int columnIndex) Retrieve the given column as bytes from the given ResultSet.
InputStream	getClobAsAsciiStream(ResultSet rs, int columnIndex) Retrieve the given column as ASCII stream from the given ResultSet.
Reader	getClobAsCharacterStream(ResultSet rs, int columnIndex) Retrieve the given column as character stream from the given ResultSet.
String	getClobAsString(ResultSet rs, int columnIndex) Retrieve the given column as String from the given ResultSet.
LobCreator	getLobCreator() Create a new LobCreator instance, i.e. a session for creating BLOBs and CLOBs.

Method Detail

getBlobAsBytes

public byte[] getBlobAsBytes(ResultSet rs,
                             int columnIndex)
                      throws SQLException

Retrieve the given column as bytes from the given ResultSet. Might simply invoke ResultSet.getBytes or work with ResultSet.getBlob, depending on the database and driver.

Parameters:

rs - the ResultSet to retrieve the content from

columnIndex - the column index to use

Returns:

the content as byte array, or null in case of SQL NULL

Throws:

SQLException - if thrown by JDBC methods

getBlobAsBinaryStream

public InputStream getBlobAsBinaryStream(ResultSet rs,
                                         int columnIndex)
                                  throws SQLException

Retrieve the given column as binary stream from the given ResultSet. Might simply invoke ResultSet.getBinaryStream or work with ResultSet.getBlob, depending on the database and driver.

Parameters:

rs - the ResultSet to retrieve the content from

columnIndex - the column index to use

Returns:

the content as binary stream, or null in case of SQL NULL

Throws:

SQLException - if thrown by JDBC methods

getClobAsString

public String getClobAsString(ResultSet rs,
                              int columnIndex)
                       throws SQLException

Retrieve the given column as String from the given ResultSet. Might simply invoke ResultSet.getString or work with ResultSet.getClob, depending on the database and driver.

Parameters:

rs - the ResultSet to retrieve the content from

columnIndex - the column index to use

Returns:

the content as String, or null in case of SQL NULL

Throws:

SQLException - if thrown by JDBC methods

getClobAsAsciiStream

public InputStream getClobAsAsciiStream(ResultSet rs,
                                        int columnIndex)
                                 throws SQLException

Retrieve the given column as ASCII stream from the given ResultSet. Might simply invoke ResultSet.getAsciiStream or work with ResultSet.getClob, depending on the database and driver.

Parameters:

rs - the ResultSet to retrieve the content from

columnIndex - the column index to use

Returns:

the content as ASCII stream, or null in case of SQL NULL

Throws:

SQLException - if thrown by JDBC methods

getClobAsCharacterStream

public Reader getClobAsCharacterStream(ResultSet rs,
                                       int columnIndex)
                                throws SQLException

Retrieve the given column as character stream from the given ResultSet. Might simply invoke ResultSet.getCharacterStream or work with ResultSet.getClob, depending on the database and driver.

Parameters:

rs - the ResultSet to retrieve the content from

columnIndex - the column index to use

Returns:

the content as character stream

Throws:

SQLException - if thrown by JDBC methods

getLobCreator

public LobCreator getLobCreator()

Create a new LobCreator instance, i.e. a session for creating BLOBs and CLOBs. Needs to be closed after the created LOBs are not needed anymore, i.e. after statement execution or transaction completion.

Returns:

the new LobCreator instance

See Also:

LobCreator.close()