Datastax java 驱动程序 4 上的 GenericDao

Question

Is the following approach to a GenericDao possible with the v4 java driver? How?

public static <T> List<?> retrieve(Class<?> clazz, BoundStatement boundStatement) throws Exception {

        List<?> tList = new ArrayList<>();
        Result<?> result = null;
        MappingManager manager = null;

        Session session = CassandraUtil.getSession();

        ResultSet resultSet = session.execute(boundStatement);

        int totRows = resultSet.getAvailableWithoutFetching();

        if (totRows > 0) {

            manager = new MappingManager(session);
            Mapper<?> m = manager.mapper(clazz);
            result = (Result<?>) m.map(resultSet);
            tList = result.all();
        }

        return tList;
    }

This approach provided tremendous productivity by using a GenericDao across the entire application.

I am assessing the changes to move to the V4 of the javadriver but I am hitting the wall as it seems not possible to do the same with the java driver V4.

Thanks

IPVP

Answer 1

You can use @GetEntity annotation on DAO to convert Row object into your POJO. You can also convert ResultSet into POJO, iterable of POJOs, etc. - depending on return value of the function. Here is example from documentation:

@Dao
public interface ProductDao {
  @GetEntity
  Product asProduct(Row row);

  @GetEntity
  PagingIterable<Product> asProducts(ResultSet resultSet);

  // ...
}

See documentation for more details.