使用Criteria Builder获取每个人的最新记录

Question

我想知道如何使用Criteria Query来生成此查询，我能够使用JPQL完成此任务，但需要使用JPA Criteria Query。 查询是：

select user_id, user_name, borrowing_date 
    from books_record b 
    where (user_id, borrowing_time) in (
    select br.user_id, max(br.borrowing_time) 
     from books_record br 
     group by br.user_id 
    ) 

Answer 1

以下条件应该工作，我没有测试它

//sub query 
DetachedCriteria subquery = DetachedCriteria.forClass(BooksRecord.class, "bk1"); 
ProjectionList proj1 = Projections.projectionList(); 
proj1.add((Projections.property("user_id").as("user_id")); 
proj1.add(Projections.max("borrowing_time").as("borrowing_time")); 
proj1.add(Projections.groupProperty("user_id")); 
subquery.setProjection(proj1); 

//main query 
Criteria mainQueryCriteria = getSession().createCriteria(BooksRecord.class, "bk2"); 
mainQueryCriteria.add(Restrictions.eqProperty("bk2.user_id", "bk1.user_id")); 
mainQueryCriteria.add(Restrictions.eqProperty("bk2.borrowing_time", "bk1.borrowing_time")); 
ProjectionList proj2 = Projections.projectionList(); 
proj2.add((Projections.property("user_id").as("user_id")); 
proj2.add(Projections.property("user_name").as("user_name")); 
proj2.add(Projections.property("borrowing_date").as("borrowing_date")); 
mainQueryCriteria.setProjection(proj2); 
mainQueryCriteria.setResultTransformer(Transformers.aliasToBean(BooksRecord.class)); 

List<BooksRecord> records = mainQueryCriteria.list();