org.springframework.jdbc.core.RowMapperResultSetExtractor Maven / Gradle / Ivy
/*
* Copyright 2002-2022 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;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import org.springframework.util.Assert;
/**
* Adapter implementation of the ResultSetExtractor interface that delegates
* to a RowMapper which is supposed to create an object for each row.
* Each object is added to the results List of this ResultSetExtractor.
*
* Useful for the typical case of one object per row in the database table.
* The number of entries in the results list will match the number of rows.
*
*
Note that a RowMapper object is typically stateless and thus reusable;
* just the RowMapperResultSetExtractor adapter is stateful.
*
*
A usage example with JdbcTemplate:
*
*
JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource); // reusable object
* RowMapper rowMapper = new UserRowMapper(); // reusable object
*
* List allUsers = (List) jdbcTemplate.query(
* "select * from user",
* new RowMapperResultSetExtractor(rowMapper, 10));
*
* User user = (User) jdbcTemplate.queryForObject(
* "select * from user where id=?", new Object[] {id},
* new RowMapperResultSetExtractor(rowMapper, 1));
*
* Alternatively, consider subclassing MappingSqlQuery from the {@code jdbc.object}
* package: Instead of working with separate JdbcTemplate and RowMapper objects,
* you can have executable query objects (containing row-mapping logic) there.
*
* @author Juergen Hoeller
* @since 1.0.2
* @param the result element type
* @see RowMapper
* @see JdbcTemplate
* @see org.springframework.jdbc.object.MappingSqlQuery
*/
public class RowMapperResultSetExtractor implements ResultSetExtractor> {
private final RowMapper rowMapper;
private final int rowsExpected;
/**
* Create a new RowMapperResultSetExtractor.
* @param rowMapper the RowMapper which creates an object for each row
*/
public RowMapperResultSetExtractor(RowMapper rowMapper) {
this(rowMapper, 0);
}
/**
* Create a new RowMapperResultSetExtractor.
* @param rowMapper the RowMapper which creates an object for each row
* @param rowsExpected the number of expected rows
* (just used for optimized collection handling)
*/
public RowMapperResultSetExtractor(RowMapper rowMapper, int rowsExpected) {
Assert.notNull(rowMapper, "RowMapper must not be null");
this.rowMapper = rowMapper;
this.rowsExpected = rowsExpected;
}
@Override
public List extractData(ResultSet rs) throws SQLException {
List results = (this.rowsExpected > 0 ? new ArrayList<>(this.rowsExpected) : new ArrayList<>());
int rowNum = 0;
while (rs.next()) {
results.add(this.rowMapper.mapRow(rs, rowNum++));
}
return results;
}
}