org.springframework.jdbc.support.lob: public interface: LobHandler

org.springframework.jdbc.support.lob
public interface: LobHandler [javadoc | source]

All Known Implementing Classes:
DefaultLobHandler, AbstractLobHandler, OracleLobHandler

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 be able to work with the provided 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 by default delegates to JDBC's direct accessor methods, avoiding java.sql.Blob and java.sql.Clob completely. DefaultLobHandler can also be configured to populate LOBs using PreparedStatement.setBlob/setClob (e.g. for PostgreSQL).

Unfortunately, Oracle 9i 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. The Oracle 10g JDBC driver should basically work with DefaultLobHandler as well, with some limitations in terms of LOB sizes.

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, use a LobHandler for fields that might typically require LOBs on some database because of the field size (take Oracle's numbers as a guideline).

Summarizing the recommended options (for actual LOB fields):

JDBC 4.0 driver: DefaultLobHandler with streamAsLob=true.
PostgreSQL: DefaultLobHandler with wrapAsLob=true.
Oracle 9i/10g: OracleLobHandler with a connection-pool-specific NativeJdbcExtractor .
For all other database drivers (and for non-LOB fields that might potentially turn into LOBs on some databases): a plain DefaultLobHandler .

Also see:

DefaultLobHandler

OracleLobHandler

java.sql.ResultSet#getBlob

java.sql.ResultSet#getClob

java.sql.ResultSet#getBytes

java.sql.ResultSet#getBinaryStream

java.sql.ResultSet#getString

java.sql.ResultSet#getAsciiStream

java.sql.ResultSet#getCharacterStream

author: Juergen - Hoeller

since: 23.12.2003 -

Method from org.springframework.jdbc.support.lob.LobHandler Summary:
getBlobAsBinaryStream, getBlobAsBinaryStream, getBlobAsBytes, getBlobAsBytes, getClobAsAsciiStream, getClobAsAsciiStream, getClobAsCharacterStream, getClobAsCharacterStream, getClobAsString, getClobAsString, getLobCreator

Method from org.springframework.jdbc.support.lob.LobHandler Detail:
public InputStream getBlobAsBinaryStream(ResultSet rs, String columnName) 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.
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.
public byte[] getBlobAsBytes(ResultSet rs, String columnName) 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.
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.
public InputStream getClobAsAsciiStream(ResultSet rs, String columnName) 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.
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.
public Reader getClobAsCharacterStream(ResultSet rs, String columnName) 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.
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.
public String getClobAsString(ResultSet rs, String columnName) 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.
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.
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 - typically after statement execution or transaction completion.