org.springframework.jdbc.support.lob

Interface LobHandler

All Known Implementing Classes:

AbstractLobHandler, 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 9i'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 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.

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 types of access. The Oracle 10g+ JDBC driver will work with DefaultLobHandler as well, with some limitations in terms of LOB sizes depending on DBMS setup; as of Oracle 11g (or actually, using the 11g driver even against older databases), there should be no need to use OracleLobHandler at all anymore.

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. Alternatively, consider using the proprietary OracleLobHandler (see below).
• Oracle 9i driver: Use OracleLobHandler with a connection-pool-specific NativeJdbcExtractor.
• 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, OracleLobHandler, 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
java.io.InputStream	getBlobAsBinaryStream(java.sql.ResultSet rs, int columnIndex) Retrieve the given column as binary stream from the given ResultSet.
java.io.InputStream	getBlobAsBinaryStream(java.sql.ResultSet rs, java.lang.String columnName) Retrieve the given column as binary stream from the given ResultSet.
byte[]	getBlobAsBytes(java.sql.ResultSet rs, int columnIndex) Retrieve the given column as bytes from the given ResultSet.
byte[]	getBlobAsBytes(java.sql.ResultSet rs, java.lang.String columnName) Retrieve the given column as bytes from the given ResultSet.
java.io.InputStream	getClobAsAsciiStream(java.sql.ResultSet rs, int columnIndex) Retrieve the given column as ASCII stream from the given ResultSet.
java.io.InputStream	getClobAsAsciiStream(java.sql.ResultSet rs, java.lang.String columnName) Retrieve the given column as ASCII stream from the given ResultSet.
java.io.Reader	getClobAsCharacterStream(java.sql.ResultSet rs, int columnIndex) Retrieve the given column as character stream from the given ResultSet.
java.io.Reader	getClobAsCharacterStream(java.sql.ResultSet rs, java.lang.String columnName) Retrieve the given column as character stream from the given ResultSet.
java.lang.String	getClobAsString(java.sql.ResultSet rs, int columnIndex) Retrieve the given column as String from the given ResultSet.
java.lang.String	getClobAsString(java.sql.ResultSet rs, java.lang.String columnName) Retrieve the given column as String from the given ResultSet.
LobCreator	getLobCreator() Create a new LobCreator instance, i.e.

Method Detail

getBlobAsBytes

byte[] getBlobAsBytes(java.sql.ResultSet rs,
                      java.lang.String columnName)
               throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getBytes(int)

getBlobAsBytes

byte[] getBlobAsBytes(java.sql.ResultSet rs,
                      int columnIndex)
               throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getBytes(int)

getBlobAsBinaryStream

java.io.InputStream getBlobAsBinaryStream(java.sql.ResultSet rs,
                                          java.lang.String columnName)
                                   throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getBinaryStream(int)

getBlobAsBinaryStream

java.io.InputStream getBlobAsBinaryStream(java.sql.ResultSet rs,
                                          int columnIndex)
                                   throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getBinaryStream(int)

getClobAsString

java.lang.String getClobAsString(java.sql.ResultSet rs,
                                 java.lang.String columnName)
                          throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getString(int)

getClobAsString

java.lang.String getClobAsString(java.sql.ResultSet rs,
                                 int columnIndex)
                          throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getString(int)

getClobAsAsciiStream

java.io.InputStream getClobAsAsciiStream(java.sql.ResultSet rs,
                                         java.lang.String columnName)
                                  throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getAsciiStream(int)

getClobAsAsciiStream

java.io.InputStream getClobAsAsciiStream(java.sql.ResultSet rs,
                                         int columnIndex)
                                  throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getAsciiStream(int)

getClobAsCharacterStream

java.io.Reader getClobAsCharacterStream(java.sql.ResultSet rs,
                                        java.lang.String columnName)
                                 throws java.sql.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:

java.sql.SQLException - if thrown by JDBC methods

See Also:

ResultSet.getCharacterStream(int)

getClobAsCharacterStream

java.io.Reader getClobAsCharacterStream(java.sql.ResultSet rs,
                                        int columnIndex)
                                 throws java.sql.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:

java.sql.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()