我在存储库中有一个方法:
public Long sumOfPrices(Specification<Order> spec) {
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Long> query = builder.createQuery(Long.class);
Root<Order> root = query.from(Order.class);
query.select(builder.sum(root.get(Order_.price)));
query.where(spec.toPredicate(root, query, builder));
return sum = em.createQuery(query).getSingleResult();
}
如何编写可分页的方法?
public Long sumOfPrices(Specification<Order> spec, Pageable pageable)
我不知道在哪里调用setMaxResult和setFirstResult,因为sum返回单个结果.
解决方法:
您可以执行以下操作:
public Page<Long> sumOfPrices(Specification<Order> spec, Pageable pageable) {
// Your Query
...
// Here you have to count the total size of the result
int totalRows = query.getResultList().size();
// Paging you don't want to access all entities of a given query but rather only a page of them
// (e.g. page 1 by a page size of 10). Right now this is addressed with two integers that limit
// the query appropriately. (http://spring.io/blog/2011/02/10/getting-started-with-spring-data-jpa)
query.setFirstResult(pageable.getPageNumber() * pageable.getPageSize());
query.setMaxResults(pageable.getPageSize());
Page<Long> page = new PageImpl<Long>(query.getResultList(), pageable, totalRows);
return page;
}
这就是我们的工作方式,希望对您有所帮助.
有关更多信息,请访问:http://spring.io/blog/2011/02/10/getting-started-with-spring-data-jpa