org.springframework.jdbc.support.lob.LobHandler Maven / Gradle / Ivy
/*
* 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 {@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.
*
*
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 {@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.
*
- Oracle 10g driver: 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.
*
- PostgreSQL: Configure {@link DefaultLobHandler} with {@code 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 {@link DefaultLobHandler}.
*
*
* @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 {@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 {@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 {@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 {@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 {@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 {@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 {@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 {@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 {@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 {@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 {@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();
}