使用 Criteria API 计算元组查询的总数？

Question

我有一个Tagtable（device_id、customer_id是这个table中的外键）:

------------------------------------------
| name | value | device_id | customer_id |
------------------------------------------
|   a  |   a   |    10     |    2389     |
------------------------------------------
|   a  |   a   |    20     |    2389     | 
------------------------------------------
|   a  |   a   |    30     |    2389     |
------------------------------------------
|tag-n | tag-v |    10     |    2389     |
------------------------------------------

我正在尝试获取带有名称和值的标签（作为搜索过滤器）并取回 device_id 计数、name 和 value。

示例： 如果我按 name = a and value = a 搜索，则响应应为：

{
  "customer_id": "2389",
  "tags": [
    {
      "name": "a",
      "value": "a",
      "device_count": 3 //since 3 devices have same name/value pairs
    }
  ],
  "pagination": {
    "offset": 0,
    "page": 0,
    "count_per_page": 1,
    "total_count": 1
  }
}

我的服务逻辑中的 Criteria 查询是：

PageRequest pageRequest = (!StringUtils.isBlank(sortBy)) ? PageRequest.of(page, limit, Sort.by(sortBy)) : PageRequest.of(page, limit);

CriteriaBuilder criteriaBuilder =  em.getCriteriaBuilder();
CriteriaQuery<Tuple> query = criteriaBuilder.createTupleQuery();
Root<TagEntity> root = query.from(TagEntity.class);
  
// add predicates

Predicate[] predArray = new Predicate[predicates.size()];
predicates.toArray(predArray);

query.multiselect(root.get(TagEntity_.name), root.get(TagEntity_.value), criteriaBuilder.count(deviceJoin.get(DeviceEntity_.ID)))
 .where(predArray).groupBy(root.get(TagEntity_.name), root.get(TagEntity_.value));
                         
TypedQuery<Tuple> typedQuery = em.createQuery(query);

//this works fine
List<Tuple> result = typedQuery
                     .setFirstResult((int) pageRequest.getOffset())
                     .setMaxResults(pageRequest.getPageSize())
                     .getResultList();

//This code fails with InvalidPathException: 'generatedAlias2.customerId'
CriteriaQuery<Long> countQuery = criteriaBuilder.createQuery(Long.class);
Root<TagEntity> tagCountRoot = countQuery.from(TagEntity.class);
countQuery.select(criteriaBuilder.count(tagCountRoot)).where(predArray);
Long count = em.createQuery(countQuery).getResultList().get(0);              
Page<Tuple> tagEntities = new PageImpl<>(result, pageRequest, count);

我的问题是如何编写总计数查询，因为在我的例子中，我得到的是 Tuple 而不是整个 TagEntity。任何帮助将不胜感激。

TIA。

P.S。我在同一个 method 中创建了 Predicates，如下所示：

List<Predicate> predicates = new ArrayList<>();

Join<TagEntity, DeviceEntity> deviceJoin = root.join(TagEntity_.deviceEntity, JoinType.LEFT);

Join<TagEntity, CustomerEntity> customerJoin = root.join(TagEntity_.customerEntity, JoinType.LEFT);
predicates.add(criteriaBuilder.equal(customerJoin.get(CustomerEntity_.customerId), customerId));

//search by exact name and exact value
predicates.add(criteriaBuilder.and(criteriaBuilder.equal(root.get(TagEntity_.name), exactName), criteriaBuilder.equal(root.get(TagEntity_.value), exactValue)));

Answer 1

您必须始终使用带分页的排序，即使是默认情况下也是如此。

计算distinct(name, value)对更简单。不要忘记对它们进行排序。

这里最好使用内连接

Join<TagEntity, CustomerEntity> customerJoin = root.join(TagEntity_.customerEntity, JoinType.LEFT);

Answer 2

问题已解决。对于可能导致 exception 的两个查询，我使用了在方法中定义的相同 predicates 数组。一个更好的方法是创建一个 specification 如下：

private Specification<TagEntity> getTagEntitySpecification(String customerId, String name, String value) {
    return (Root<TagEntity> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) -> {
       List<Predicate> predicates = new ArrayList<>();
       
       Join<TagEntity, CustomerEntity> customerJoin = root.join(TagEntity_.customerEntity, JoinType.INNER);
       predicates.add(criteriaBuilder.equal(customerJoin.get(CustomerEntity_.customerId), customerId));

      //search by name and value
      predicates.add(criteriaBuilder.and(criteriaBuilder.equal(root.get(TagEntity_.name), exactName),
                        criteriaBuilder.equal(root.get(TagEntity_.value), exactValue)));
      
      return criteriaBuilder.and(predicates.toArray(new Predicate[0]));
    };
}

在 where 子句中使用 specification.toPredicate(root, criteriaQuery, criteriaBuilder) 如下所示：

final Specification<TagEntity> specification = getTagEntitySpecification(customerId, name, value);

// query 1
query.multiselect(root.get(TagEntity_.name), root.get(TagEntity_.value),criteriaBuilder.count(deviceJoin.get(DeviceEntity_.ID))).where(specification.toPredicate(root, query, criteriaBuilder)).groupBy(root.get(TagEntity_.name), root.get(TagEntity_.value));

//count query
countQuery.select(cbCount.count(tagCountRoot)).where(specification.toPredicate(tagCountRoot, countQuery, cbCount));
Long count = em.createQuery(countQuery).getResultList().get(0);
tagEntities = new PageImpl<>(result, pageRequest, count);

使用 Criteria API 计算元组查询的总数？

Calculate total count for a tuple query using Criteria API?

java

jpa

criteria-api

hibernate-criteria

spring-boot