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.

  * <p/>

  * <p>

  * 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.

  * <p/>

  * <p>

  * Note that a RowMapper object is typically stateless and thus reusable; just the RowMapperResultSetExtractor adapter

  * is stateful.

  * <p/>

  * <p>

  * A usage example with JdbcTemplate:

  * <p/>

  * 

  * <pre class="code">

  * JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);  // reusable object

  * RowMapper rowMapper = new UserRowMapper();  // reusable object

  * <p/>

  * List allUsers = (List) jdbcTemplate.query(

  * "select * from user",

  * new RowMapperResultSetExtractor(rowMapper, 10));

  * <p/>

  * User user = (User) jdbcTemplate.queryForObject(

  * "select * from user where id=?", new Object[] {id},

  * new RowMapperResultSetExtractor(rowMapper, 1));

  * </pre>

  * <p/>

  * 

  * @author Spring Framework

  * @see RowMapper

  * @see liquibase.executor.Executor

  */

 @SuppressWarnings({ "unchecked" })

 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;

     }

     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;

     }

 }