https://github.com/spring-projects/spring-framework: Spring JDBC (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2018 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
 *
 *      http://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.core.support;

import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.dao.DataAccessException;
import org.springframework.dao.EmptyResultDataAccessException;
import org.springframework.dao.IncorrectResultSizeDataAccessException;
import org.springframework.jdbc.LobRetrievalFailureException;
import org.springframework.jdbc.core.ResultSetExtractor;
import org.springframework.lang.Nullable;


Abstract ResultSetExtractor implementation that assumes streaming of LOB data.
Typically used as inner class, with access to surrounding method arguments.

Delegates to the streamData template method for streaming LOB content to some OutputStream, typically using a LobHandler. Converts an IOException thrown during streaming to a LobRetrievalFailureException. 
A usage example with JdbcTemplate:

JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);  // reusable object
final LobHandler lobHandler = new DefaultLobHandler();  // reusable object
jdbcTemplate.query(
	 "SELECT content FROM imagedb WHERE image_name=?", new Object[] {name},
	 new AbstractLobStreamingResultSetExtractor() {
		 public void streamData(ResultSet rs) throws SQLException, IOException {
			 FileCopyUtils.copy(lobHandler.getBlobAsBinaryStream(rs, 1), contentStream);
            }
        }
);


Author:Juergen Hoeller
Type parameters:
  • <T> – the result type
See Also:
Since:1.0.2
/**
 * Abstract ResultSetExtractor implementation that assumes streaming of LOB data.
 * Typically used as inner class, with access to surrounding method arguments.
 *
 * <p>Delegates to the {@code streamData} template method for streaming LOB
 * content to some OutputStream, typically using a LobHandler. Converts an
 * IOException thrown during streaming to a LobRetrievalFailureException.
 *
 * <p>A usage example with JdbcTemplate:
 *
 * <pre class="code">JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);  // reusable object
 * final LobHandler lobHandler = new DefaultLobHandler();  // reusable object
 *
 * jdbcTemplate.query(
 *		 "SELECT content FROM imagedb WHERE image_name=?", new Object[] {name},
 *		 new AbstractLobStreamingResultSetExtractor() {
 *			 public void streamData(ResultSet rs) throws SQLException, IOException {
 *				 FileCopyUtils.copy(lobHandler.getBlobAsBinaryStream(rs, 1), contentStream);
 *             }
 *         }
 * );</pre>
 *
 * @author Juergen Hoeller
 * @since 1.0.2
 * @param <T> the result type
 * @see org.springframework.jdbc.support.lob.LobHandler
 * @see org.springframework.jdbc.LobRetrievalFailureException
 */
public abstract class AbstractLobStreamingResultSetExtractor<T> implements ResultSetExtractor<T> {

	
Delegates to handleNoRowFound, handleMultipleRowsFound and streamData,
according to the ResultSet state. Converts an IOException thrown by
streamData to a LobRetrievalFailureException.

See Also:
/**
	 * Delegates to handleNoRowFound, handleMultipleRowsFound and streamData,
	 * according to the ResultSet state. Converts an IOException thrown by
	 * streamData to a LobRetrievalFailureException.
	 * @see #handleNoRowFound
	 * @see #handleMultipleRowsFound
	 * @see #streamData
	 * @see org.springframework.jdbc.LobRetrievalFailureException
	 */
	@Override
	@Nullable
	public final T extractData(ResultSet rs) throws SQLException, DataAccessException {
		if (!rs.next()) {
			handleNoRowFound();
		}
		else {
			try {
				streamData(rs);
				if (rs.next()) {
					handleMultipleRowsFound();
				}
			}
			catch (IOException ex) {
				throw new LobRetrievalFailureException("Couldn't stream LOB content", ex);
			}
		}
		return null;
	}

	
Handle the case where the ResultSet does not contain a row.

Throws:
  • DataAccessException – a corresponding exception,
by default an EmptyResultDataAccessException
See Also:
/**
	 * Handle the case where the ResultSet does not contain a row.
	 * @throws DataAccessException a corresponding exception,
	 * by default an EmptyResultDataAccessException
	 * @see org.springframework.dao.EmptyResultDataAccessException
	 */
	protected void handleNoRowFound() throws DataAccessException {
		throw new EmptyResultDataAccessException(
				"LobStreamingResultSetExtractor did not find row in database", 1);
	}

	
Handle the case where the ResultSet contains multiple rows.

Throws:
  • DataAccessException – a corresponding exception,
by default an IncorrectResultSizeDataAccessException
See Also:
/**
	 * Handle the case where the ResultSet contains multiple rows.
	 * @throws DataAccessException a corresponding exception,
	 * by default an IncorrectResultSizeDataAccessException
	 * @see org.springframework.dao.IncorrectResultSizeDataAccessException
	 */
	protected void handleMultipleRowsFound() throws DataAccessException {
		throw new IncorrectResultSizeDataAccessException(
				"LobStreamingResultSetExtractor found multiple rows in database", 1);
	}

	
Stream LOB content from the given ResultSet to some OutputStream.

Typically used as inner class, with access to surrounding method arguments
and to a LobHandler instance variable of the surrounding class.

Params:
  • rs – the ResultSet to take the LOB content from
Throws:
See Also:
/**
	 * Stream LOB content from the given ResultSet to some OutputStream.
	 * <p>Typically used as inner class, with access to surrounding method arguments
	 * and to a LobHandler instance variable of the surrounding class.
	 * @param rs the ResultSet to take the LOB content from
	 * @throws SQLException if thrown by JDBC methods
	 * @throws IOException if thrown by stream access methods
	 * @throws DataAccessException in case of custom exceptions
	 * @see org.springframework.jdbc.support.lob.LobHandler#getBlobAsBinaryStream
	 * @see org.springframework.util.FileCopyUtils
	 */
	protected abstract void streamData(ResultSet rs) throws SQLException, IOException, DataAccessException;

}