【阿里】浅谈DDD中的聚合

//订单明细实体
public class OrderItemEntity {
  //id
  private Long id;
  //商品(值对象)
  private Product product;
  //数量(值对象)
  private Count count;
  // item总价(值对象)
  private ItemAmount itemAmt;
  
  public void modifyCount(Count count) {
    this.count = count;
    this.itemAmt = new ItemAmt(this.product.getPrice()*count.get());
  }
  
}

//订单聚合根
public class OrderAggregate {
  //聚合唯一标识
  private Long id;
  //订单号(值对象)
  private OrderNo orderNo;
  //总价 (值对象)
  private Amount amt;
  //订单明细
  private List<OrderItemEntity> items;
  
  public void modifyItemCount(Product product,Count count) {
    //找到商品
    this.items.stream().filter(product::equals).findAny().get();
    //修改数量 返回Item总价
    item.modifyCount(count);
    ItemAmount itemAmt = item.getItemAmt();
    //修改订单总价
    this.amt = new Amount(this.amt.get()+itemAmt.get());
  }
  
}

//要订单明细中 名称叫电脑的商品数量修改100

Product product = new Product("电脑");
Count count = new Count(100);
Amount amt = orderAggregate.modifyItemCount(product, count);

public class OrderAggregate {
  //聚合唯一标识
  private Long id;
  //订单号(值对象)
  private OrderNo orderNo;
  //总价 (值对象)
  private Amount amt;
  //关联对象接口（接口实现在基础服务层，在实现中操作数据库）
  private OrderItemRel orderItemRel;

  
 public void modifyItemCount(Product product,Count count) {
    List<OrderItemEntity> items = orderItemRel.find(product);
    //找到商品
    OrderItemEntity item = items.stream().filter(product::equals).findAny().get();
    //修改数量 返回Item总价 这里有分支,item修改是否应该在modifyCount中持久化
    //1.modifyCount中持久化item那么数据库事务将被加载AppcationService层，容易产生大事务问题。
    //2.modifyCount中不持久化item 
    //2.1写入消息总线，当OrderAggregate通过Reponsitory持久化时刷出消息持久化
    //2.2 OrderAggregate中增加List<OrderItemEntity> items,modifyCount将item加入items。
    item.modifyCount(count);
    ItemAmount itemAmt = item.getItemAmt();
    //修改订单总价
    this.amt = new Amount(this.amt.get()+itemAmt.get());
    return this.amt;
  }
}

//订单明细聚合
public class OrderItemAggregate {
  //id
  private Long id;
  //商品(值对象)
  private Product product;
  //数量(值对象)
  private Count count;
  // item总价(值对象)
  private ItemAmount itemAmt;
  //Order实体
  private OrderEntity orderEntity;
  
  public void modifyCount(Count count) {
    this.count = count;
    ItemAmt itemAmt = new ItemAmt(this.product.getPrice()*this.count.get());
    //order总价
    Amt amt = this.orderEntity.getAmt();
    //总价-item总价+新item总价
    amt = new Amt(amt.get() - this.ItemAmt.get() + itemAmt.get());
    //变更订单总价
    this.orderEntity.modifyAmt(amt);
    this.itemAmt = itemAmt;
  }
  
}

//订单实体
public class OrderEntity {
  //聚合唯一标识
  private Long id;
  //订单号(值对象)
  private OrderNo orderNo;
  //总价 (值对象)
  private Amount amt;
  
  public Amount modifyAmt(Amt amt) {
    //修改订单总价
    this.amt = amt;
  }
  
}

//要订单明细中 名称叫电脑的商品数量修改100
orderItemAggregate.modifyCount(count);