org.springframework/spring-jdbc/5.3.3 : org/springframework/jdbc/support/lob/LobHandler.java

LobHandler
https://github.com/spring-projects/spring-framework: Spring JDBC (Spring IO)
Apache License, Version 2.0
Juergen Hoeller
/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.support.lob;

import java.io.InputStream;
import java.io.Reader;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.lang.Nullable;

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. 
Author: Juergen Hoeller
See Also: DefaultLobHandler
ResultSet.getBlob
ResultSet.getClob
ResultSet.getBytes
ResultSet.getBinaryStream
ResultSet.getString
ResultSet.getAsciiStream
ResultSet.getCharacterStream
Since: 23.12.2003/**
 * Abstraction for handling large binary fields and large text fields in
 * specific databases, no matter if represented as simple types or Large OBjects.
 *
 * <p>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.
 *
 * <p>Most databases/drivers should be able to work with {@link DefaultLobHandler},
 * which by default delegates to JDBC's direct accessor methods, avoiding the
 * {@code java.sql.Blob} and {@code java.sql.Clob} API completely.
 * {@link DefaultLobHandler} can also be configured to access LOBs using
 * {@code PreparedStatement.setBlob/setClob} (e.g. for PostgreSQL), through
 * setting the {@link DefaultLobHandler#setWrapAsLob "wrapAsLob"} property.
 *
 * <p>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).
 *
 * <p><b>Summarizing the recommended options (for actual LOB fields):</b>
 * <ul>
 * <li><b>JDBC 4.0 driver (including Oracle 11g driver):</b> Use {@link DefaultLobHandler},
 * potentially with {@code streamAsLob=true} if your database driver requires that
 * hint when populating a LOB field. Fall back to {@code createTemporaryLob=true}
 * if you happen to run into LOB size limitations with your (Oracle) database setup.
 * <li><b>Oracle 10g driver:</b> Use {@link 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.
 * <li><b>PostgreSQL:</b> Configure {@link DefaultLobHandler} with {@code wrapAsLob=true},
 * and use that LobHandler to access OID columns (but not BYTEA) in your database tables.
 * <li>For all other database drivers (and for non-LOB fields that might potentially
 * turn into LOBs on some databases): Simply use a plain {@link DefaultLobHandler}.
 * </ul>
 *
 * @author Juergen Hoeller
 * @since 23.12.2003
 * @see DefaultLobHandler
 * @see java.sql.ResultSet#getBlob
 * @see java.sql.ResultSet#getClob
 * @see java.sql.ResultSet#getBytes
 * @see java.sql.ResultSet#getBinaryStream
 * @see java.sql.ResultSet#getString
 * @see java.sql.ResultSet#getAsciiStream
 * @see java.sql.ResultSet#getCharacterStream
 */
public interface LobHandler {

	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. 
Params: rs – the ResultSet to retrieve the content from
columnName – the column name to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getBytes
Returns: the content as byte array, or null in case of SQL NULL/**
	 * Retrieve the given column as bytes from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getBytes} or work with
	 * {@code ResultSet.getBlob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnName the column name to use
	 * @return the content as byte array, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getBytes
	 */
	@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. 
Params: rs – the ResultSet to retrieve the content from
columnIndex – the column index to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getBytes
Returns: the content as byte array, or null in case of SQL NULL/**
	 * Retrieve the given column as bytes from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getBytes} or work with
	 * {@code ResultSet.getBlob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnIndex the column index to use
	 * @return the content as byte array, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getBytes
	 */
	@Nullable
	byte[] getBlobAsBytes(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. 
Params: rs – the ResultSet to retrieve the content from
columnName – the column name to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getBinaryStream
Returns: the content as binary stream, or null in case of SQL NULL/**
	 * Retrieve the given column as binary stream from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getBinaryStream} or work with
	 * {@code ResultSet.getBlob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnName the column name to use
	 * @return the content as binary stream, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getBinaryStream
	 */
	@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. 
Params: rs – the ResultSet to retrieve the content from
columnIndex – the column index to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getBinaryStream
Returns: the content as binary stream, or null in case of SQL NULL/**
	 * Retrieve the given column as binary stream from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getBinaryStream} or work with
	 * {@code ResultSet.getBlob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnIndex the column index to use
	 * @return the content as binary stream, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getBinaryStream
	 */
	@Nullable
	InputStream getBlobAsBinaryStream(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. 
Params: rs – the ResultSet to retrieve the content from
columnName – the column name to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getString
Returns: the content as String, or null in case of SQL NULL/**
	 * Retrieve the given column as String from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getString} or work with
	 * {@code ResultSet.getClob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnName the column name to use
	 * @return the content as String, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getString
	 */
	@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. 
Params: rs – the ResultSet to retrieve the content from
columnIndex – the column index to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getString
Returns: the content as String, or null in case of SQL NULL/**
	 * Retrieve the given column as String from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getString} or work with
	 * {@code ResultSet.getClob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnIndex the column index to use
	 * @return the content as String, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getString
	 */
	@Nullable
	String getClobAsString(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. 
Params: rs – the ResultSet to retrieve the content from
columnName – the column name to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getAsciiStream
Returns: the content as ASCII stream, or null in case of SQL NULL/**
	 * Retrieve the given column as ASCII stream from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getAsciiStream} or work with
	 * {@code ResultSet.getClob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnName the column name to use
	 * @return the content as ASCII stream, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getAsciiStream
	 */
	@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. 
Params: rs – the ResultSet to retrieve the content from
columnIndex – the column index to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getAsciiStream
Returns: the content as ASCII stream, or null in case of SQL NULL/**
	 * Retrieve the given column as ASCII stream from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getAsciiStream} or work with
	 * {@code ResultSet.getClob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnIndex the column index to use
	 * @return the content as ASCII stream, or {@code null} in case of SQL NULL
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getAsciiStream
	 */
	@Nullable
	InputStream getClobAsAsciiStream(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. 
Params: rs – the ResultSet to retrieve the content from
columnName – the column name to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getCharacterStream
Returns: the content as character stream/**
	 * Retrieve the given column as character stream from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getCharacterStream} or work with
	 * {@code ResultSet.getClob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnName the column name to use
	 * @return the content as character stream
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getCharacterStream
	 */
	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. 
Params: rs – the ResultSet to retrieve the content from
columnIndex – the column index to use
Throws: SQLException – if thrown by JDBC methods
See Also: ResultSet.getCharacterStream
Returns: the content as character stream/**
	 * Retrieve the given column as character stream from the given ResultSet.
	 * Might simply invoke {@code ResultSet.getCharacterStream} or work with
	 * {@code ResultSet.getClob}, depending on the database and driver.
	 * @param rs the ResultSet to retrieve the content from
	 * @param columnIndex the column index to use
	 * @return the content as character stream
	 * @throws SQLException if thrown by JDBC methods
	 * @see java.sql.ResultSet#getCharacterStream
	 */
	Reader getClobAsCharacterStream(ResultSet rs, int columnIndex) throws SQLException;

	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. 
See Also: LobCreator.close()
Returns: the new LobCreator instance/**
	 * Create a new {@link 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.
	 * @return the new LobCreator instance
	 * @see LobCreator#close()
	 */
	LobCreator getLobCreator();

}
Author:	Juergen Hoeller
See Also:	DefaultLobHandler ResultSet.getBlob ResultSet.getClob ResultSet.getBytes ResultSet.getBinaryStream ResultSet.getString ResultSet.getAsciiStream ResultSet.getCharacterStream
Since:	23.12.2003
Params:	rs – the ResultSet to retrieve the content from columnName – the column name to use
Throws:	SQLException – if thrown by JDBC methods
See Also:	ResultSet.getBytes
Returns:	the content as byte array, or `null` in case of SQL NULL
See Also:	LobCreator.close()
Returns:	the new LobCreator instance
/

org.springframework/ spring-jdbc/ 5.3.3/ org/springframework/jdbc/support/lob/LobHandler.java
