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I am writing spring data jpa using Specification. but the IDEA give me a error(red line): 

'select(javax.persistence.criteria.Selection<? extends capture<?>>)' in 'javax.persistence.criteria.CriteriaQuery' cannot be applied to '(javax.persistence.criteria.Root<cn.lvxg.po.ClassRoom>)'

here is my code. please help me!

the Root is subclass of Selection. why my code is wrong?

I am really suffering from this problem.

    Specification<Student> specification = new Specification<Student>() {
        public Predicate toPredicate(Root<Student> root,//
                                     CriteriaQuery<?> criteriaQuery,
                                     CriteriaBuilder criteriaBuilder) {
            Root<ClassRoom> classRoomRoot = criteriaQuery.from(ClassRoom.class);
            Root<Student> studentRoot = criteriaQuery.from(Student.class);
            criteriaQuery.select(classRoomRoot)
                    .distinct(true)
                    .where(criteriaBuilder.equal(studentRoot,classRoomRoot.get("id")));
            return criteriaQuery.getRestriction();;

        }

    };
    Pageable pageable = new PageRequest(0, 5);
    Page<Student> studentsPage = jpaSpecificationRepository.findAll(specification, pageable);
Neil Stockton
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usrmqj xv
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1 Answers1

0

Should be only one Root in a query.

Vitalii Muzalevskyi
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