org.springframework.jdbc.support.lob

Interface LobHandler

All Known Implementing Classes:

AbstractLobHandler, DefaultLobHandler

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.

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 in order 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 the java.sql.Blob and java.sql.Clob API completely. DefaultLobHandler can also be configured to access LOBs using PreparedStatement.setBlob/setClob (e.g. for PostgreSQL), through setting the "wrapAsLob" property.

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 (including Oracle 11g driver): Use DefaultLobHandler, potentially with streamAsLob=true if your database driver requires that hint when populating a LOB field. Fall back to createTemporaryLob=true if you happen to run into LOB size limitations with your (Oracle) database setup.
• Oracle 10g driver: Use DefaultLobHandler with standard setup. On Oracle 10.1, set the "SetBigStringTryClob" connection property; as of Oracle 10.2, DefaultLobHandler should work with standard setup out of the box.
• PostgreSQL: Configure DefaultLobHandler with wrapAsLob=true, and use that LobHandler to access OID columns (but not BYTEA) in your database tables.
• For all other database drivers (and for non-LOB fields that might potentially turn into LOBs on some databases): Simply use a plain DefaultLobHandler.

Since:

23.12.2003

Author:

Juergen Hoeller

See Also:

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

Method Summary

Modifier and Type	Method and Description
InputStream	getBlobAsBinaryStream(ResultSet rs, int columnIndex) Retrieve the given column as binary stream from the given ResultSet.
InputStream	getBlobAsBinaryStream(ResultSet rs, String columnName) 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.
byte[]	getBlobAsBytes(ResultSet rs, String columnName) 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.
InputStream	getClobAsAsciiStream(ResultSet rs, String columnName) 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.
Reader	getClobAsCharacterStream(ResultSet rs, String columnName) 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.
String	getClobAsString(ResultSet rs, String columnName) Retrieve the given column as String from the given ResultSet.
LobCreator	getLobCreator() Create a new LobCreator instance, i.e.

Method Detail

getBlobAsBytes

@Nullable
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.

Parameters:

rs - the ResultSet to retrieve the content from

columnName - the column name to use

Returns:

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

Throws:

SQLException - if thrown by JDBC methods

See Also:

ResultSet.getBytes(int)

getBlobAsBytes

@Nullable
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

See Also:

ResultSet.getBytes(int)

getBlobAsBinaryStream

@Nullable
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.

Parameters:

rs - the ResultSet to retrieve the content from

columnName - the column name to use

Returns:

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

Throws:

SQLException - if thrown by JDBC methods

See Also:

ResultSet.getBinaryStream(int)

getBlobAsBinaryStream

@Nullable
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

See Also:

ResultSet.getBinaryStream(int)

getClobAsString

@Nullable
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.

Parameters:

rs - the ResultSet to retrieve the content from

columnName - the column name to use

Returns:

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

Throws:

SQLException - if thrown by JDBC methods

See Also:

ResultSet.getString(int)

getClobAsString

@Nullable
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

See Also:

ResultSet.getString(int)

getClobAsAsciiStream

@Nullable
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.

Parameters:

rs - the ResultSet to retrieve the content from

columnName - the column name to use

Returns:

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

Throws:

SQLException - if thrown by JDBC methods

See Also:

ResultSet.getAsciiStream(int)

getClobAsAsciiStream

@Nullable
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

See Also:

ResultSet.getAsciiStream(int)

getClobAsCharacterStream

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.

Parameters:

rs - the ResultSet to retrieve the content from

columnName - the column name to use

Returns:

the content as character stream

Throws:

SQLException - if thrown by JDBC methods

See Also:

ResultSet.getCharacterStream(int)

getClobAsCharacterStream

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

See Also:

ResultSet.getCharacterStream(int)

getLobCreator

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.

Returns:

the new LobCreator instance

See Also:

LobCreator.close()