Spring Data Jpa 复杂查询方式总结(多表关联及自定义分页)

@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;
}

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

@RunWith(SpringRunner.class)
@SpringBootTest
public class TCityRepositoryTest{
     @Autowired
    private TCityRepository tCityRepository;
}

/**
 * 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);

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

/**
 * 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);

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

/**
 * 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);

/**
 * 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);

/**
* 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;
        }
}

@Test
public void findCityAndHotelByHQLResultObj() throws Exception {
    List<CityHohel> cityAndHotelByHQLResultObj = tCityRepository.findCityAndHotelByHQLResultObj("酒店");
    Assert.assertTrue(cityAndHotelByHQLResultObj.size() > 0);
}

/**
 * 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);
}

@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);
}

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

public class StudentRepositoryImpl implements StudentCoustomRepository {
     
    // 这里可以写很复杂的SQL,作为演示之用,就不弄那么复杂
    private static final String SQL = "select * from t_student where name like :name ";     
    @PersistenceContext
    private EntityManager em; 
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Override
    public List<StudentVO> findByName(String name) {
        Query query = em.createNativeQuery(SQL).setParameter("name", "%"+name+"%");
        query.unwrap(SQLQuery.class).setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);
        List queryList = query.getResultList();
         
        if (queryList.size() == 0) {
            System.out.println("找不到Student name为" + name + "的记录");
            return null;
        }         
        List<StudentVO> retVal = new ArrayList<>();
        for(Object o : queryList) {
            Map student = (Map)o;
            StudentVO vo = new StudentVO();
            try {
                // org.apache.commons.beanutils.BeanUtils;
                // 使用apaches的beanutil,直接吧map转为实例
                BeanUtils.populate(vo, student);
                retVal.add(vo);
            } catch (IllegalAccessException | InvocationTargetException e) {
                System.out.println("解析StudentVO bean时发生异常：" + e.getMessage());
            }
        }
        return retVal;
    }
}