如何在Spring Data中實現包含兩個相同類型的實體列表的實體

Question

我有實體訂單。 它包含玻璃零件清單和非玻璃零件清單。 零件是具有屬性PartType（玻璃/非玻璃）的單個實體。 請問這對Spring Data可行嗎？ 怎么樣？ 我正在將Spring Boot 1.3.1.RELEASE與Hibernate一起使用。

@Entity
@Table(name="order")
public class Order {

    ...

    @OneToMany(...)
    private List<Part> glassParts;

    @OneToMany(...)
    private List<Part> otherParts;
}

@Entity
@Table(name="part")
public class Part {

  ...

  @Column(...)
  private PartType partType;

  @Column(...)
  private String code;

  @Column(...)
  private String description;
}

Answer 1

我相信在您的情況下，創建兩個列表不是一個好主意。 為了獲得結果，有兩種常用方法。 第一個是創建雙向關系，並在適當的條件下實現存儲庫和管理器層：

@Entity
@Table(name="order")
public class Order {

    ...

    @OneToMany(mappedBy = "order", fetch = FetchType.LAZY, cascade = { ... })
    private List<Part> parts;
}

@Entity
@Table(name="part")
public class Part {

  ...

  @JoinColumn(name = "r_order_id", referencedColumnName = "id")
  @ManyToOne(...)  
  private Order order;
  @Column(...)
  private PartType partType;

  @Column(...)
  private String code;

  @Column(...)
  private String description;
}

public interface PartInterface implements CrudRepository<Part, Long> {

  List<Part> findByOrderIdAndPartType(Long orderId, PartType partType);
}

@Component
public class PartManager {

  @Autowired
  private PartInterface partInterface;

  public List<Part> getGlassPartsByOrderId(Long orderId) {
    return List<Part> partInterface.findByOrderIdAndPartType(orderId, PartType.GLASS);
  }

  public List<Part> getNonGlassPartsByOrderId(Long orderId) {
    return List<Part> partInterface.findByOrderIdAndPartType(orderId, PartType.NON_GLASS);
  }
}

第二個是按類型過濾訂單的所有部分：

public interface OrderInterface implements CrudRepository<Order, Long> {

  @Override
  Order findOne(Long orderId);
}

@Component
public class OrderManager {

  @Autowired
  private OrderInterface orderInterface;

  public List<Part> getGlassPartsByOrderId(Long orderId) {    
    return getOrderParts(orderId).stream().filter(part -> Objects.equals(PartType.GLASS, part.getPartType())).collect(Collectors.toList());    
  }

  public List<Part> getNonGlassPartsByOrderId(Long orderId) {
    return getOrderParts(orderId).stream().filter(part -> Objects.equals(PartType.NON_GLASS, part.getPartType())).collect(Collectors.toList());    
  }

  private List<Part> getOrderParts(Long orderId) {
    Order order = orderInterface.findOne(Long orderId);
    if (Objects.isNull(order) || Objects.isNull(order.getParts())) {
      return Collections.emptyList();
    } else {
      return order.getParts();
    }
  }
}

實際上，還有另一種選擇-動態過濾實體內部的零件：

@Entity
@Table(name="order")
public class Order {

    @OneToMany(...)
    private List<Part> parts;

    public List<Part> getGlassParts{
      if (Objects.nonNull(parts)) {
        return parts.stream().filter(part -> Objects.equals(PartType.GLASS, part.getPartType())).collect(Collectors.toList());
      } else {
        return Collections.emptyList();
      }
    }

    public List<Part> getNonGlassParts{
      if (Objects.nonNull(parts)) {
        return parts.stream().filter(part -> Objects.equals(PartType.NON_GLASS, part.getPartType())).collect(Collectors.toList());
      } else {
        return Collections.emptyList();
      }
    }
}

更新由於您使用的是Hibernate因此有一個依賴ORM的選項來獲得所需的結果，它是一個@JoinColumnOrFormula批注，僅可用於Hibernate ：

@Entity
@Table(name="order")
public class Order {

    @OneToMany(...)
    @JoinColumnOrFormula(
      column = @JoinColumn(name = "id", referencedColumnName = "r_order_id", insertable = false, updatable = false)
      ,formula = @JoinFormula(value = PartType.GLASS_STR_VALUE, referencedColumnName = "partType"))
    private List<Part> glassParts;

    @OneToMany(...)
    @JoinColumnOrFormula(
      column = @JoinColumn(name = "id", referencedColumnName = "r_order_id", insertable = false, updatable = false)
      ,formula = @JoinFormula(value = PartType.NON_GLASS_STR_VALUE, referencedColumnName = "partType"))
    private List<Part> nonGlassParts;    
}

請注意@JoinFormula子句中的value參數必須為String