liquibase.executor.jvm.RowMapperResultSetExtractor Maven / Gradle / Ivy
package liquibase.executor.jvm;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
/**
* 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));
*
*
* @author Spring Framework
* @see RowMapper
* @see liquibase.executor.Executor
*/
@SuppressWarnings({"unchecked"})
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) {
this.rowMapper = rowMapper;
this.rowsExpected = rowsExpected;
}
@Override
public Object 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;
}
}