T result from repository finder should throw exception when there is not a single unique result [DATAGRAPH-948]

[spring-projects-issues]

Mark Angrish opened DATAGRAPH-948 and commented

SDN should follow Spring Data conventions where it can.

??"T | An unique entity. Expects the query method to return one result at most. In case no result is found null is returned. More than one result will trigger an IncorrectResultSizeDataAccessException."??

From: https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repository-query-return-types

Test case:

    @Test(expected = IncorrectResultSizeDataAccessException.class)
    public void findByNameSingleResult() throws Exception {
        World world1 = new World("world 1", 1);
        worldRepository.save(world1, 0);

        World world2 = new World("world 1", 2);
        worldRepository.save(world2, 0);

        World world = worldRepository.findByName("world 1"); // there are 2 results, 1 is returned instead of IncorrectResultSizeDataAccessException thrown
    }

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Affects: 4.2 RC1 (Ingalls), 5.0 M1 (Kay)

[spring-projects-issues]

Gerrit Meier commented

Due to refactoring driven by DATAGRAPH-975 this was already resolved.
Added regression test for completeness