org.springframework.jdbc.core

## Class RowMapperResultSetExtractor<T>

- java.lang.Object
- - org.springframework.jdbc.core.RowMapperResultSetExtractor<T>

- All Implemented Interfaces:
    ResultSetExtractor<List<T>>

      public class RowMapperResultSetExtractor<T>
      extends Object
      implements ResultSetExtractor<List<T>>

  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 `jdbc.object` package: Instead of working with separate JdbcTemplate and RowMapper objects, you can have executable query objects (containing row-mapping logic) there.

  Since:
    1.0.2
  Author:
    Juergen Hoeller
  See Also:
    `RowMapper`, `JdbcTemplate`, `MappingSqlQuery`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `RowMapperResultSetExtractor(RowMapper<T> rowMapper)` Create a new RowMapperResultSetExtractor.
    `RowMapperResultSetExtractor(RowMapper<T> rowMapper, int rowsExpected)` Create a new RowMapperResultSetExtractor.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `List<T>` | `extractData(ResultSet rs)` Implementations must implement this method to process the entire ResultSet.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### RowMapperResultSetExtractor

          public RowMapperResultSetExtractor(RowMapper<T> rowMapper)

      Create a new RowMapperResultSetExtractor.
      Parameters:
        `rowMapper` - the RowMapper which creates an object for each row

    - #### RowMapperResultSetExtractor

          public RowMapperResultSetExtractor(RowMapper<T> rowMapper,
                                     int rowsExpected)

      Create a new RowMapperResultSetExtractor.
      Parameters:
        `rowMapper` - the RowMapper which creates an object for each row
        `rowsExpected` - the number of expected rows (just used for optimized collection handling)

  - ### Method Detail

    - #### extractData

          public List<T> extractData(ResultSet rs)
                              throws SQLException

      Description copied from interface: `ResultSetExtractor`
      Implementations must implement this method to process the entire ResultSet.
      Specified by:
        `extractData` in interface `ResultSetExtractor<List<T>>`
      Parameters:
        `rs` - ResultSet to extract data from. Implementations should not close this: it will be closed by the calling JdbcTemplate.
      Returns:
        an arbitrary result object, or `null` if none (the extractor will typically be stateful in the latter case).
      Throws:
        `SQLException` - if a SQLException is encountered getting column values or navigating (that is, there's no need to catch SQLException)