SPRING data REST :How to select specific field from the repository

Question

In the following query I want to select only shopname from the order but when I execute the query it gives me an error of PersistentEntity must not be null I have searched this problem but I can't find any solution How can I get only selected rows from the Order table ?

OrderRepository

public interface OrderRepository extends JpaRepository<Order, Long> {
@Query("Select o.shopName from Order o where o.customer.id= :customerId ")
     String selectUsersOrder(@Param("customerId") Long customerId );
}

Order.class

@Entity
@Table(name="CustomerOrder")
public class Order implements Serializable,OrderGetters {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column( nullable = false, updatable = false, insertable = false, columnDefinition = "TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
    @Temporal(TemporalType.TIMESTAMP)
    private Date orderDate ;

    @OneToMany(mappedBy="order",targetEntity=OrderItem.class)
    private List<OrderItem> orderitem;

    @Temporal(TemporalType.TIMESTAMP)
    private Date completionDate ;

    @Enumerated(EnumType.STRING)
    private OrderStatus orderStatus;

    @Enumerated(EnumType.STRING)
    private DeliveryStatus deliveryStatus;



    private String riderInstruction;

    @Enumerated(EnumType.STRING)
    private OrderType orderType;

    @ManyToOne
    private User customer;


    @OneToOne
    private User rider;

    @OneToOne
    private Address dropOffAddress;

    @OneToOne
    private Address pickupAddress;

    private String receiverName;

    private String promoCode;

    private String shopName;

    private float shoppingPrice;

    private float orderPrice;

    private float cashCollected;

    ..... Getter and setters
    }

You can use JPA projections. Check out [this](https://stackoverflow.com/a/39189023/3094731) answer. — Abdullah Khan, Jun 13 '17 at 08:10
If the answer helped you don't forget to accept/upvote it... — Cepr0, Jun 21 '17 at 14:04

score 0 · Answer 1 · answered Jun 13 '17 at 12:32

You may use the nativeQuery property of Spring by setting the nativeQuery value to 'true':

@Query("SELECT ShopName FROM CustomerOrder WHERE CustomerId = ?1", nativeQuery = true)
String selectUsersOrder(Long customerId);

or you can cast it to an Object[] first while fetching, than take the value you want from this object.

score 0 · Answer 2 · answered Jun 13 '17 at 13:35

You should use Projection and delete your custom method from the Repo.

@Projection(name = "onlyShopName", types = {Order.class})
public interface OnlyShopName { 

    String getShopName();
}

Then GET your orders like this:

GET http://localhost:8080/orders?projection=onlyShopName

SPRING data REST :How to select specific field from the repository

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