自定义查询，用于从Spring Data Jpa中的多个表中获取数据

自定义查询，用于从Spring Data Jpa中的多个表中获取数据

您的查询不是hibernate有效的有效HQL查询。您可以使用本机SQL查询，但是使用HQL可以轻松实现上述用例。在此之前，让我们为ManytoMany关联使用正确的注释映射：

@Entity@Table(name = "order_detail")public class OrderDetail {     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Integer id;     @ManyToOne     @JoinColumn(name="purchased_By")     private user PurchasedBy;     @ManyToMany     @JoinTable(       name="order_detail_productlist",       joinColumns=@JoinColumn(name="order_detail_id", referencedColumnName="id"),       inverseJoinColumns=@JoinColumn(name="productlist_id", referencedColumnName="id"))      private Set<Product> productlist = new HashSet<Product>();

产品：

@Entity@Table(name ="product")public class Product implements Serializable {      @Id      @GeneratedValue(strategy = GenerationType.AUTO)      private Integer id;      @NotNull(message = "Product name must not be null")      @NotEmpty      @Column(name = "name", nullable = false)      private String name;      @ManyToOne      @JoinColumn(name="category_id")      private Category category;      @ManyToMany(mappedBy = "productlist")      private List<OrderDetail> orderDetail =new ArrayList<OrderDetail>();

并查询：

public final static String product_ordered ="Select p from Product p Join p.orderDetail od Where od.id = :id";@Query(product_ordered)public List<Product> findById(@Param("id") int id);

这是从JPA开始的初学者友好资源