无法从类型[java.lang.Object[]]转换为类型[@org.springframework.data.jpa.repository.Query

Question

我有使用JPA/Hibernate、MySQL的Spring boot项目。我有三个多对多关系的道类。

Poko类如下所示

产品

@Entity
@Table(name = "product")
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false, columnDefinition = "integer")
    private Integer id;
    @Column(name = "name")
    private String name;
    @Column(name = "price")
    private Double price;

    @ManyToMany(cascade = {
            CascadeType.PERSIST,
            CascadeType.MERGE
    })
    @JoinTable(
            name = "product_extra",
            joinColumns = @JoinColumn(name="product_id"),
            inverseJoinColumns = @JoinColumn(name="extra_id")
    )
    private List<Extra> extras = new ArrayList<>();

  //constructor getters and setters
}

ProductExtra公司

@Entity
@Table(name = "product_extra")
public class ProductExtra {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false, columnDefinition = "integer")
    private Integer id;
    @Column(name = "product_id")
    private Integer productId;
    @Column(name = "extra_id")
    private Integer extraId;

   //constructor getters and setter
}

额外的

@Entity
@Table(name = "extra")
public class Extra {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false, columnDefinition = "integer")
    private Integer id;
    @Column(name = "name")
    private String name;
    @Column(name = "price")
    private Double price;

    @ManyToMany(mappedBy = "extras")
    private List<Product> products = new ArrayList<>();

    //constructor getters and setters
}

包含查询的额外存储库

public interface ExtraRepository extends JpaRepository<Extra, Integer> {
    @Query("SELECT e.id, e.name, e.price FROM Extra e INNER JOIN ProductExtra pe ON e.id = pe.extraId WHERE pe.productId = ?1")
    List<Extra> findExtraById(Integer productId);
}

控制器中的映射

@GetMapping("/product/{productId}")
    public List<Extra>getExtraById(@PathVariable("productId") final Integer productId){
        return extraRepository.findExtraById(productId);
    }

我试图进行多对多的查询来选择每个产品中的附加功能，但是我得到了这个错误未能从类型[java.lang.对象[]]转换为类型[@org.springframework.data.jpa.repository.查询错误消息令人惊讶地也包含我想要的结果。不确定我做错了什么

Answer 1

删除SELECT子句：

@Query("FROM Extra join e.productExtra WHERE pe.productId = ?1")

还要记住，您不是编写SQL查询，而是处理对象，所以对于join，您使用mapped属性