JPA Repository method List<Integer> returns result as List<BigDecimal> why?

Question

I have next method in JPA Repository kartDao:

@Query(value = "select t.k_lsk_id from SCOTT.KART t ", nativeQuery = true)
List<Integer> findAllKlskId();

When I try to fetch it using:

List<Integer> someLst = new ArrayList<Integer>();
someLst.add(12); // my Integer value
someLst.addAll(kartDao.findAllKlskId());

I see in debugger that someList contains both Integer and BigDecimal types:

But how it happens? My someList is List type!! Can't understand, help me))

upd1 In Oracle database the k_lsk_id type is Number:

Answer 1

The culprit is this line of code I think. It tries to convert the result of the query execution. If it fails to find a converter it just returns the original unconverted result.

The converter used is essentially a DefaultConversionService which doesn't support any convertions from BigDecimal .

UPDATE: I looked a little more into this, and it seems that the problem is not so much that the conversion service can't convert BigDecimal , but that the requested target type is simply List .

I opened an issue and will look into it.

Answer 2

Number return decimal value form the DB side.

you should have to change the number to Integer