Spring Data JPA Query method to find all objects with empty list property

Question

I have an entity which contains a property that is a list:

@Entity
@Table(name="sales.jobs")
public class Job {
    ...
    private List<Shipment> jobShipments;
    ...
    @OneToMany(cascade=CascadeType.ALL,orphanRemoval=true, fetch=FetchType.LAZY)
    @JoinTable(name="sales.jobs_shipments",
           joinColumns = @JoinColumn(name="fk_jobid", referencedColumnName="pk_jobid"),
           inverseJoinColumns = @JoinColumn(name="fk_shipmentid", referencedColumnName="pk_shipmentid"))
    public List<Shipment> getJobShipments() {
        return jobShipments;
    }

    public void setJobShipments(List<Shipment> jobShipments) {
        this.jobShipments = jobShipments;
    }
    ...
}

In the repository, I would like to have a query method which returns all jobs where jobShipments is an empty list. I had first tried the IsNull keyword as shown below, but that doesn't work because if there are no shipments it is an empty list rather than null.

@Repository
public interface JobRepository extends CrudRepository<Job, Integer> {
    Page<Job> findByJobShipmentsIsNull(Pageable pageable);
}

I looked through the keywords in the documentation hoping to find something like IsEmpty, but I couldn't find anything that looked right.

I am looking for an answer that uses keywords rather than writing out a query, but I suppose that would be the fallback. Thanks!

Answer 1

Actually, there're keywords IsEmpty and Empty for collections:

@Repository
public interface JobRepository extends CrudRepository<Job, Integer> {
    Page<Job> findByJobShipmentsIsEmpty(Pageable pageable);
}

@Entity
@Table(name="sales.jobs")
public class Job {
    ...
    @OneToMany(cascade=CascadeType.ALL,orphanRemoval=true, fetch=FetchType.LAZY)
    @JoinTable(name="sales.jobs_shipments",
           joinColumns = @JoinColumn(name="fk_jobid", referencedColumnName="pk_jobid"),
           inverseJoinColumns = @JoinColumn(name="fk_shipmentid", referencedColumnName="pk_shipmentid"))
    private List<Shipment> jobShipments = new ArrayList<Shipment>();
}

See Appendix C: Repository Query Keywords.