如何在 Spring 数据中实现包含两个相同类型实体列表的实体

Question

我有实体订单。它包含玻璃零件列表和非玻璃零件列表。部件是属性为部件类型(玻璃/非玻璃(的单个图元。这可以用弹簧数据吗？如何？我正在使用带有Hibernate的Spring Boot 1.3.1.RELEASE。

@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

我相信在您的情况下，创建两个列表不是一个好主意。要获得结果，有两种常见的方法。第一个是创建双向关系，并在适当的条件下实现存储库和管理器层：

@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);
}
}

第二个是按类型过滤订单的所有部分：

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();
}
}
}

实际上还有另一种选择 - 动态过滤实体内的零件：

@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();
}
}
}

更新由于您使用的是Hibernate因此有一个依赖于ORM的选项来获得所需的结果，因此它是一个@JoinColumnOrFormula注释，仅适用于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;    
}

请注意，@JoinFormula子句中的value参数必须是String