如何从具有外键类型的JPA存储库中返回选择查询

Question

I am trying to do this:

@Query(value = "SELECT DISTINCT c.* FROM comarca c INNER JOIN debito_negativacao d ON d.comarca_id = c.id WHERE d.status = :status", nativeQuery = true)
List<Comarca> findDistinctComarcaByStatus(@Param("status") String status);

But I get this error:

  org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.Object[]] to type [com.hc.projects.model.Comarca] for value '{9, 0, 7323}'; nested exception is org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.math.BigInteger] to type [com.hc.projects.model.Comarca]

Answer 1

You have to return all columns that are necessary to construct a Comarca. So you will have to join the table.

As didn't provide the tables I can only guess:

@Query(value = "SELECT DISTINCT * FROM comarca c " +
                "JOIN debito_negativacao d ON d.comarca_id = c.id "+
                "WHERE d.debito_negativacao.status= :status", nativeQuery = true)
List<Comarca> findDistinctComarcaIdByStatus(@Param("status") String status);

Answer 2

Your request tells that you want a list of BigInteger : SELECT DISTINCT comarca_id... because comarca_id is a biginteger I guess. If you want a Comarca list, you have to request on all your table.

Answer 3

If you want to use a distinct query that will return other columns than the distinct one you need some kind of strategy how to "merge" the objects. Imagine rows like this:

------------------------------
| comarca_id| key | status    |
| 1         | A   | your_state|
| 1         | B   | your_state|
| 2         | C   | your_state|
------------------------------

What would you get in this case?

SELECT DISTINCT comarca_id FROM comarca; will return 1,2

However, how can you merge two (or more) entries which have the same comarca_id and status ?

This leaves you with three cases:

1. you assume comarca_id + status is unique -> you don't need the DISTINCT query
2. There might be more than one row with same comarca_id and status -> you can't make the query distinct
3. you only want the distinct comarca_id values -> make your method return List<BigInteger>

Answer 4

If, in a second time, you want to isolate a list of comarca_id, try to stream your request result.

    List<Comarca> comarca = debitoNegativacao.stream().map(dn -> dn.getComarca()).distinct().collect(Collectors.toList());

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