Let’s say you are using Spring Data and you have a “Composite Key” (ie, a tuple or EmbeddedId). Generally, you may want to query by the whole composite key (ie, by ID), which is generally fairly straightforward with a JPA “query method” (still not sure that is the official name). Even so, one of the reasons you use tuples or composite keys is to group data (and maybe even group within a group). Running with that thought, let’s say you have the following composite key:
@NoArgsConstructor
@AllArgsConstructor
@Data
@Embeddable
public class PlantScheduleCompositeKey implements Serializable {
@Column(name = "state")
private String state;
@Column(name = "city")
private String city;
@Column(name = "zip")
private String zip;
@Column(name = "crop")
private String crop;
} Next, let’s use the composite key in this Entity:
@Entity
@Data
@Table(name="plant_schedule")
public class PlantSchedule implements Serializable {
@EmbeddedId
private PlantScheduleCompositeKey id;
private boolean frostDates;
private boolean moonDates;
private String sowSeedsIndoorSchedule;
private String transplantSeedlingsSchedule;
private String directSowSchedule;
private String source;
} Now, if you are using a CrudRepository, or better yet a PagingAndSortingRepository, you’ll already get findById() out of the box. This will not help us if we want to search by only city, state, and zip (ie, without the crop name). So, we need to craft a custom query method, which will be turned into JPQL behind the scenes.
@RepositoryRestResource
public interface IPlantScheduleRepository extends PagingAndSortingRepository<PlantSchedule, PlantScheduleCompositeKey>{
public List<PlantSchedule> findAllByIdCityContainingAndIdStateContainingAndIdZipContaining(String city, String state, String zip, Pageable pageable);
} The key here is to understand that there is a hierarchy here with a filter that is repeated for the 3 out of the 4 parts of the composite key we want to search against. We can interpret the substring IdCityContaining as being the field id on the entity PlantSchedule, followed by the part of the composite key we want to do a contains comparison against. Therefore, we repeat this pattern twice more for state and zip. So, in summary, we have a query method that will return all PlantSchedules with a city, state, and zip matching the provided arguments.
Sample call:
Pageable pageable = PageRequest.of(0, 100);
List<PlantSchedule> pageList = plantScheduleRepository.findAllByIdCityContainingAndIdStateContainingAndIdZipContaining(city, state, zip, pageable);
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