Spring Data Jpa 复杂查询总结 (多表关联 以及 自定义分页 )

实体类

@Entity
@Table(name = "t_hotel")
@Data
public class THotel {
    @Id
    private int id;
    private String name;
    private String address;
    /**
     * 城市id
     */
    private String city;
}

@Entity
@Table(name = "t_city")
@Data
public class TCity {
    @Id
    private int id;
    private String name;
    private String state;
    private String country;
    private String map;

}

新建接口

public interface TCityRepository extends JpaRepository<TCity, Integer>, JpaSpecificationExecutor<TCity> {

}

单元测试类

@RunWith(SpringRunner.class)
@SpringBootTest
public class TCityRepositoryTest{

     @Autowired
    private TCityRepository tCityRepository;
}

1.查找出Id小于3,并且名称带有shanghai的记录.

/**
 * 查找出Id小于3,并且名称带有`shanghai`的记录.
 *
 * @param id   id
 * @param name 城市名称
 * @return 城市列表
 */
List<TCity> findByIdLessThanAndNameLike(int id, String name);

单元测试

@Test
public void findByIdLessThanAndNameLike() throws Exception {
    List<TCity> shanghai = tCityRepository.findByIdLessThanAndNameLike(3, "%shanghai%");
    Assert.assertTrue(shanghai.size() > 0);
}

2.通过旅店名称分页查询旅店以及城市的所有信息

/**
 * 通过旅店名称分页查询旅店以及城市的信息
 *
 * @param name     旅店名称
 * @param pageable 分页信息
 * @return Page<Object[]>
 */
@Query(value = "select t1.name as cityName,t2.name as hotelName\n" +
        "from t_city t1\n" +
        "  left join t_hotel t2 on t2.city = t1.id\n" +
        "where t2.name = :name",
        countQuery = "select count(*)" +
                "from t_city t1 \n" +
                "  left join t_hotel t2 on t2.city = t1.id\n" +
                "where t2.name = :name"
        , nativeQuery = true)
Page<Object[]> findCityAndHotel(@Param("name") String name, Pageable pageable);

为了节约时间 我只在select 与 from 之间 分别查询了城市的名称以及旅店的名称如果要查所有的信息,可以换成 
t1.* , 
t2.*

单元测试

@Test
public void findCityAndHotel() throws Exception {
    Page<Object[]> cityAndHotel = tCityRepository.findCityAndHotel("酒店", new PageRequest(0, 10));
    Assert.assertTrue(cityAndHotel.getTotalElements() > 0);
} 

3.HQL通过旅店名称查询旅店以及城市的所有信息

3和2其实是一样的,为了方便我就不作出分页查询了

HQL可以用map来接受返回的参数,具体的用法如下所示:

/**
 * HQL通过旅店名称查询旅店以及城市的所有信息
 *
 * @return
 */
@Query(value = "select new map(t1,t2) from  TCity t1 left  join THotel t2 on t1.id=t2.city where t2.name =:name")
List<Map<String, Object>> findCityAndHotelByHQL(@Param("name") String name);

测试方法和2是差不多的 我就不粘贴了

Map

4.HQL通过旅店名称查询旅店以及城市的所有信息 直接返回实体类

/**
 * 关联查询
 *
 * @return
 */
@Query(value = "select new pers.zpw.domain.CityHohel(t1.name AS cityName,t2.name AS hotelName) from  TCity t1 left  join THotel t2 on t1.id=t2.city where t2.name =:name")
List<CityHohel> findCityAndHotelByHQLResultObj(@Param("name") String name);

为了方便CityHohel我只封装了2个属性,这和HQL查询的字段是完全一致的,也必须要保持一致.

/**
* Created by ZhuPengWei on 2018/5/12.
*/
@Data
public class CityHohel {

        private String cityName;
        private String hotelName;

        public CityHohel(String cityName, String hotelName) {
            this.cityName = cityName;
            this.hotelName = hotelName;
        }
}

当然这个带参的构造方法是必须要写的,否则会抛出转换实体的异常

单元测试

@Test
public void findCityAndHotelByHQLResultObj() throws Exception {

    List<CityHohel> cityAndHotelByHQLResultObj = tCityRepository.findCityAndHotelByHQLResultObj("酒店");
    Assert.assertTrue(cityAndHotelByHQLResultObj.size() > 0);
}

4.HQL通过旅店名称分页查询旅店以及城市的所有信息 直接返回实体类

/**
 * 关联查询
 *
 * @return
 */
@Query(value = "select new pers.zpw.domain.CityHohel(t1.name AS cityName,t2.name AS hotelName) from  TCity t1 left  join THotel t2 on t1.id=t2.city where t2.name =:name",
        countQuery = "select count(*) from  TCity t1 left  join THotel t2 on t1.id=t2.city where t2.name =:name")
Page<CityHohel> findCityAndHotelAllSelf(@Param("name") String name, Pageable pageable);

    @Test
public void findCityAndHotelAllSelf() throws Exception {
    Page<CityHohel> cityAndHotelAllSelf = tCityRepository.findCityAndHotelAllSelf("酒店", new PageRequest(0, 10));

    Assert.assertTrue(cityAndHotelAllSelf.getTotalElements() > 0);
}

5.动态查询旅店以及城市的所有信息 直接返回实体类

如果是动态查询的话当然首先得构造一条sql去查询了,当然如果不是自定义实体对象的话这样的网上一大堆我就不写了.

直接走测试

@Autowired
@PersistenceContext
private EntityManager entityManager;

@Test
public void testDynamic() throws Exception {
        String sql = "select new pers.zpw.domain.CityHohel(t1.name AS cityName,t2.name AS hotelName) from  TCity t1 left  join THotel t2 on t1.id=t2.city where t2.name =‘酒店‘";
        Query query = entityManager.createQuery(sql);
        List resultList = query.getResultList();
        Assert.assertTrue(resultList.size() > 0);
}

这样测试是通过的,因此可以知道在业务层的方法中我们可以动态的构造SQL语句. 比如说可以在接口中这样子来定义一个方法

 /**
 * 自定义查询
 * @param sql
 * @param entityManager
 * @return
 */
default List customQuery(String sql, EntityManager entityManager) {
    return entityManager.createQuery(sql).getResultList();
}

然后在测试类中动态的根据条件去拼接SQL语句去调用

转载:https://blog.csdn.net/qq_36144258/article/details/80298354

原文地址：https://www.cnblogs.com/icebutterfly/p/9506021.html