org.springframework.jdbc.core.support.AbstractLobStreamingResultSetExtractor Maven / Gradle / Ivy
/*
* Copyright 2002-2019 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.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 {@code 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
* @since 1.0.2
* @param the result type
* @see org.springframework.jdbc.support.lob.LobHandler
* @see org.springframework.jdbc.LobRetrievalFailureException
*/
public abstract class AbstractLobStreamingResultSetExtractor implements ResultSetExtractor {
/**
* 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("Could not 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 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 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.
* @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;
}