如何对 JPA 查询进行分页 [英] How to paginate a JPA Query

问题描述

我有一个提交表，其中包含诸如 ID、Name、Code 等列以及其他属性.我的要求是根据提到的属性搜索记录并返回一个分页集.

I have a submission table with columns like ID, Name, Code among other properties. My requirement is to search for records based on the mentioned properties and return a paginated set.

这是我要找的伪代码:

searchSubmission(searchFilter sf,pageIndex,noOfRecords) {
   query = 'from submisssion where code=sf.code or id=sf.id order by id start_from (pageIndex*noOfRecords) limit noOfRecords'
   return result();
}

似乎有很多选项，例如 CriteriaBuilder、NamedQuery 等.在这种情况下哪个最有效?

There seem to be many options like CriteriaBuilder, NamedQuery, etc. Which is the most efficient one in this situation?

推荐答案

对于所有 JPA 查询对象(本机 SQL 查询除外)，您将通过 setMaxResults(int) 和 setFirstResult(int) 方法使用分页.例如:

For all JPA query objects (except for native SQL queries), you would use pagination through the setMaxResults(int) and setFirstResult(int) methods. For instance:

  return em.createNamedQuery("yourqueryname", YourEntity.class)
      .setMaxResults(noOfRecords)
      .setFirstResult(pageIndex * noOfRecords)
      .getResultList();

JPA 将为您执行分页.

JPA will perform the pagination for you.

命名查询只是预定义的，可以缓存，而其他类型是动态创建的.
所以选择是使用 JPQL，如:

Named queries are just predefined and can be cached, while other types are dynamically created.
So the choice is to use JPQL like:

Query query = em.createQuery("SELECT s FROM Submission s WHERE s.code = :code or s.id = :id ORDER BY s.id", Submission.class);

或 CriteriaBuilder api 形成类似的查询:

Or CriteriaBuilder api to form a similar query:

    CriteriaBuilder qb = em.getCriteriaBuilder();
    CriteriaQuery<Submission> cq = qb.createQuery(Submission.class);

    Root<Submission> root = cq.from(Submission.class);
    cq.where( qb.or( 
        qb.equal(root.get("code"), qb.parameter(String.class, "code")),
        qb.equal(root.get("id"), qb.parameter(Integer.class, "id"))
    ));
    Query query = em.createQuery(cq);

不要忘记使用例如 query.setParameter("id", sf.id) 设置参数值.

Don't forget to set the parameter values using query.setParameter("id", sf.id) for example.

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