如何限制Spring Data Repository中使用的@Query的结果

Question

我正在 Spring Data JPA 中按CrudRepository检索数据。我想过滤从@Query注释中提供的自定义查询中检索到的记录。我为.setMaxResults(20);尝试了select rows..但是它给出了错误。我想从我的表中过滤前20行

这是我的资料库

package lk.slsi.repository;

import java.util.Date;
import lk.slsi.domain.SLSNotification;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.repository.query.Param;

import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;

/**
 * Created by ignotus on 2/10/2017.
 */
public interface SLSNotificationRepository extends CrudRepository<SLSNotification, Integer> {


    @Override
    SLSNotification save(SLSNotification slsNotification);

    @Override
    SLSNotification findOne(Integer snumber);

    @Override
    long count();

    @Override
    void delete(Integer integer);

    @Override
    void delete(SLSNotification slsNotification);

    @Override
    void delete(Iterable<? extends SLSNotification> iterable);

    @Override
    List<SLSNotification> findAll();

    @Query("select a from SLSNotification a where a.slsiUnit in :unitList order by snumber desc")
    List<SLSNotification> getApplicationsByUnit(@Param("unitList") List<String> unitList);

    @Query("select a from SLSNotification a where a.userId = :userId")
    List<SLSNotification> getApplicationsByUserId(@Param("userId") String userId);

    @Query("select a.snumber, a.date, a.slsNo, a.slsiUnit, a.productDesc, a.status from SLSNotification a where a.userId = :userId ORDER BY snumber desc")
    List<SLSNotification> getApplicationsByUserIdforManage(@Param("userId") String userId);

    @Query("select a from SLSNotification a where a.slsNo = :slsNo")
    SLSNotification getApplicationBySLSNumber(@Param("slsNo") String slsNo);

}

我希望我的List<SLSNotification> getApplicationsByUserIdforManage(@Param("userId") String userId);方法检索有限的数据集。我怎样才能打电话给实体经理或其他什么东西呢？

请帮我这样做。

Answer 1

您可以在SQL中通过Hi testuser1, Welcome to the Sample App! Click on the link below to activate your account: https://still-beyond-10331.herokuapp.com/account_activations/0MwIEqEXZaLzmWJb8KhGOg/edit?email=testuser1%40testemail1.com 语句提供限制。并在limit注释中设置nativeQuery = true，以便将JPA提供程序视为@Query SQL查询。

native

或

如果您想利用 Spring Data JPA 的强大功能  你可以通过适当的方法命名

来做到这一点

@Query(nativeQuery = true, value = "select * from SLSNotification s where s.userId = :userId ORDER BY snumber desc LIMIT 20")
List<SLSNotification> getUserIdforManage(@Param("userId") String userId);

如果您还不知道，Spring Data JPA会根据方法名称构造Query。太棒了吧？请阅读此documentation以便更好地理解。

你刚刚离开称这个方法就像

List<SLSNotification> findByUserIdOrderBySNumber(@Param("userId") String userId, Pageable pageable);

此外，如果您使用的是Java 8

您可以利用在界面中使用默认方法的功能，并使事情变得更加便利

Pageable topTwenty = new PageRequest(0, 20);
List<SLSNotification> notifications = repository.findByUserIdOrderBySNumber("101", topTwenty);