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package online.sanen.unabo.template;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.mhdt.toolkit.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 LazyToShow
* Date: 2018年10月14日
* Time: 下午2:33:10
*/
public class ResultSetExtractor2List implements ResultSetExtractor> {
private final RowExtractor rowMapper;
private final int rowsExpected;
/**
* Create a new RowMapperResultSetExtractor.
*
* @param rowMapper the RowMapper which creates an object for each row
*/
public ResultSetExtractor2List(RowExtractor 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 ResultSetExtractor2List(RowExtractor rowMapper, int rowsExpected) {
Assert.notNull(rowMapper, "RowMapper is required");
this.rowMapper = rowMapper;
this.rowsExpected = rowsExpected;
}
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;
}
}