How to get top results using specifications in spring data jpa?

Question

I am quite new to spring data jpa. I am trying to use specifications while querying database. My question is using crudrepository we can method like :

findTopByUsernameOrderByUpdatedAtDesc(String username);

How can I achieve the same using specifications? I can do basic things like and or in specifications, but not very robust like we can do with criteria etc.

Specification<CustomClass> spec = Specifications.where(specification).and(username);
List<CustomClass> list = findAll(spec);

removed the part about asking for tutorials and stuff, because it makes an otherwise good question off topic. — Jens Schauder, Jan 05 '18 at 12:01
Actually I would `order` the result list and you get your result in top place. — mrkernelpanic, Jan 05 '18 at 12:27
you asked with the half information, specification can build with the predicate and Query builders — AdamIJK, Jan 05 '18 at 13:25

score 3 · Accepted Answer · edited Oct 30 '19 at 15:17

3

This was done as follows :

 Pageable pageable = new PageRequest(0, 1, Sort.Direction.DESC, "username");
 Page oneElementPage = repository.findAll(spec, pageable);

This will sort the data on username column in descending direction and return first result.

edited Oct 30 '19 at 15:17

Markus Pscheidt

6,853
5
55
76

answered Feb 02 '18 at 17:53

Nakul Kumar

325
1
5
11

score 1 · Answer 2 · answered Jan 05 '18 at 13:00

1

You can't express this in a Specification directly. But you can use a Pageable for this:

Page oneElementPage = repository.findAll(spec, new PageRequest(0, 1));

Gives you a Page with a single element.

answered Jan 05 '18 at 13:00

Jens Schauder

77,657
34
181
348

Will this be fine : Pageable pageable = PageRequest(0, 1, Sort.Direction.DESC, "username"); and then pass this to findAll(spec,pageable); ? – Nakul Kumar Jan 06 '18 at 06:05
Think so. Just try it. – Jens Schauder Jan 06 '18 at 06:34

How to get top results using specifications in spring data jpa?

2 Answers2