import javax.persistence.*;
import java.util.Set;

@Entity
@Table(name="product")
public class Product {
  @Id
  private Long prod_id;
  private String title;

  @ManyToOne
  @JoinColumn(name="category")
  private Category category;

  @OneToMany(mappedBy = "product")
  private Set<Custom_fields> custom_fields;

  @ManyToOne
  @JoinColumn(name="manufacturer")
  private Manufacturer manufacturer;

  @OneToMany(mappedBy = "product")
  private Set<Product_image> img;

  private Double sale;
  private Double price;
  private Long quantity;
  private java.sql.Timestamp date_added;
  private String description;

import javax.persistence.*;

@Entity
@Table(name="product_image")
public class Product_image {
  @Id
  private Long img_id;
  private String path;
  private String alt;
  private String title;

  @ManyToOne
  @JoinColumn(name = "product_id")
  private Product product;