public class StudentBaseRepositoryImpl implements StudentBaseRepositoryCustom {
    @Autowired
    @PersistenceContext
    private EntityManager entityManager;

    @Override
    public List<Object[]> groupByStudentAsSql() {
        List<Object[]> list = entityManager
                .createNativeQuery("select address,count(*) from t_student group by address")
                .getResultList();

        return list;
    }

    @Override
    public List<Object[]> groupByStudentAsHql() {
        List<Object[]> list = entityManager
                .createQuery("select address,count(*) from Student group by address")
                .getResultList();
        return list;
    }

    @Override
    public List<Object[]> groupByStudentAsSpecification() {
        //根據地址分組查詢，並且學生數量大於3的所有地址
        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        CriteriaQuery<Object[]> query = builder.createQuery(Object[].class);
        Root<Student> root = query.from(Student.class);
        query.multiselect(root.get("address"),builder.count(root.get("id")))
                .groupBy(root.get("address")).having(builder.gt(builder.count(root.get("id")),3));

        return entityManager.createQuery(query).getResultList();
    }
}