使用具有 jpa 规格的 spring 数据按特定顺序按多个值排序

Question

I have a query

select * from docs
where status_id in ('105', '55', '65', '228016')
order by
case status_id
    when '55' then 1
    when '228016' then 2
    when '65' then 3
    when '105' then 4
end;

How to rewrite it in spring data with specifications?

p2 = repository.findAll(new DocsRepository.DocsSpec(filter, type), 
PageRequest.of(page, size, Sort.by(Sort.Order.desc("status"))));

Answer 1

This answer helped me

1. Created OrderByField class

    import javax.persistence.criteria.Expression; import javax.persistence.criteria.Order; public class OrderByField implements Order { private Expression<?> expression; public OrderByField(Expression<?> expression) { this.expression = expression; } @Override public Order reverse() { return null; } @Override public boolean isAscending() { return true; } @Override public Expression<?> getExpression() { return expression; } }

2. Created expression with criteriaBuilder's selectCase function

    Expression searchedCaseExpression = criteriaBuilder.selectCase().when(criteriaBuilder.equal(root.get("status").get("code"), "55"), "1").when(criteriaBuilder.equal(root.get("status").get("code"), "228016"), "2").when(criteriaBuilder.equal(root.get("status").get("code"), "65"), "3").when(criteriaBuilder.equal(root.get("status").get("code"), "105"), "4"); OrderByField order = new OrderByField(searchedCaseExpression); criteriaQuery.orderBy(order);

And don't forget to remove Sort.by from findAll(), since we're sorting with criteriaBuilder

    p2 = repository.findAll(new DocsRepository.DocsSpec(filter, type), PageRequest.of(page, size));

And one more thing, although JPA 2.x supports CASE in JPQL it is not supported in ORDER BY clauses. This might go unnoticed, though, as Hibernate's implementation of JPQL, for instance, does support CASE in ORDER BY