We already have map(Function) method available in both ColumnSelect
and SQLSelect that allows to map result from Object[] to anything via
provided function.
Here is an example from tests [1]:
List<ArtistDataWrapper> result = SQLSelect.columnQuery("SELECT * FROM
ARTIST_CT",
Integer.class, String.class, LocalDateTime.class)
.map(ArtistDataWrapper::new)
.select(context);
And I experimented with simple PojoMapper that does almost exactly
what you are suggesting. Not sure if it's available though.
[1]
https://github.com/apache/cayenne/blob/336f0e5297fe6ccdc3b1904ab4f6ee2c6d1ab9dc/cayenne-server/src/test/java/org/apache/cayenne/query/SQLSelectIT.java#L273
On Thu, Jul 14, 2022 at 10:52 PM Andrus Adamchik <aadamc...@gmail.com> wrote:
>
> Java 17 "records" create some interesting possibilities as quick DTOs.
> Mapping complex SQL is still rather painful in Cayenne. You'd get an Object[]
> as a result and/or need complex scripting within SQL. I think records and
> some API tweaks can help:
>
> 1. SQL result mapping.
>
> record MyRecord(String lastName, String firstName) {} // non-persistent, not
> in DataMap
>
> SQLSelect.query("select * from x")
>
> // new API analogous to "#result" directive but simpler to use
> // also we can implement some implicit name conversions ("AB_C" -> "abC")
> .resultColumn(0, "firstName")
> .resultColumn("LAST_NAME", "lastName")
>
> // new API - auto-mapping the result to a POJO (record in this case)
> .selectAs(MyRecord.class, context);
>
>
> 2. Entity result mapping (e.g. a replacement of column and data row queries).
>
> class MyEntity extends _MyEntity {} // Persistent
> record MyEntityDTO(..) {} // non-persistent, not in DataMap
>
> List<MyEntityDTO> result = ObjectSelect(MyEntity.class)
> .where(MyEntity.NAME.like("Joe"))
> .prefetch(MyEntity.ANOTHER.joint())
>
> // new API - auto-mapping the result to a POJO (record in this case)
> .selectAs(MyEntityDTO.class, context);
>
> It will be faster than fetching MyEntity (without ObjectContext registration,
> uniquing, merging), and will be a good replacement of column queries API,
> requiring no explicit column declarations, and producing a specific type
> instead of Object[]. Prefetches can be auto-mapped to record hierarchies.
>
> Both examples would work with either records or regular POJOs, it is just
> that record definitions are so easy to create on the spot, that they can be
> used in a multitude of very narrow contexts.
>
> Andrus
>
--
Best regards,
Nikita Timofeev
