前因简介

    在工作过程中使用 Java Bean 作为容器盛放数据日常工作。我在工作过程中发现了这么一个问题：
    业务主体是，对一个订单进行拆分。订单分为主体部分和明细部分，明细可以有多个，拆分之后对订单重新整理计算总金额。具体业务比这个要复杂，此处简单说明问题产生的部分。

业务模拟

    此处定义 class Order,class OrderHead,OrderDetail 作为 Java 对象，并定义简单的属性，如下所示：

@Setter
@Getter
class Order {private OrderHead orderHead;private List<OrderDetail> orderDetails;
}@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
class OrderHead {private String orderId;private String productName;private String orderMoney;
}@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
class OrderDetail {private String detailId;private String detailName;private String detailMoney;
}

    因为在具体业务中涉及到多种拆分方式，此处订单的拆分和重新计算总金额分开写在两个部分。此处模拟金额大于20的放在一个订单中，其他放在另外一个订单中，具体方法代码：

private void resetMoney(List<Order> result) {for (Order order : result) {BigDecimal money = new BigDecimal(0);for (OrderDetail orderDetail : order.getOrderDetails()) {money = money.add(new BigDecimal(Double.valueOf(orderDetail.getDetailMoney())));}order.getOrderHead().setOrderMoney(String.valueOf(money));}
}private void split(Order order, List<Order> result) {List<OrderDetail> orderDetails = order.getOrderDetails();Order order1 = new Order();Order order2 = new Order();List<OrderDetail> orderDetails1 = new ArrayList<>();List<OrderDetail> orderDetails2 = new ArrayList<>();for (OrderDetail orderDetail : orderDetails) {if (Double.valueOf(orderDetail.getDetailMoney()) >= 20) {orderDetails1.add(orderDetail);} else {orderDetails2.add(orderDetail);}}order1.setOrderDetails(orderDetails1);order2.setOrderDetails(orderDetails2);order1.setOrderHead(order.getOrderHead());order2.setOrderHead(order.getOrderHead());result.add(order1);result.add(order2);
}

此处咋一看没什么问题，就是对订单明细进行拆分，订单主体部分分别放到两个订单里，但是具体测试的时候就有问题了，测试代码如下：

private static JavaBeanRelation relation = new JavaBeanRelation();// 需求把 订单 a 中的 明细 拆分，大于20的单独拆分成一个订单，并重新计算head的总金额，得到最后的两个订单
public static void main(String[] args) {Order order = new Order();OrderDetail detail1 = new OrderDetail("d1", "dname1", "24");OrderDetail detail2 = new OrderDetail("d2", "dname2", "25");OrderDetail detail3 = new OrderDetail("d3", "dname3", "15");OrderDetail detail4 = new OrderDetail("d4", "dname4", "16");OrderHead orderHead = new OrderHead("b1", "bname1", "80");order.setOrderHead(orderHead);List<OrderDetail> orderDetails = new ArrayList<>();orderDetails.add(detail1);orderDetails.add(detail2);orderDetails.add(detail3);orderDetails.add(detail4);order.setOrderDetails(orderDetails);List<Order> result = new ArrayList<>();relation.split(order, result);relation.resetMoney(result);//输出最后结果JsonUtils为序列化工具类System.out.println(JsonUtils.getInstance().toJsonString(result));
}

控制台输出结果：

[{"orderDetails": [{"detailId": "d1","detailMoney": "24","detailName": "dname1"},{"detailId": "d2","detailMoney": "25","detailName": "dname2"}],"orderHead": {"orderId": "b1","orderMoney": "31","productName": "bname1"}},{"orderDetails": [{"detailId": "d3","detailMoney": "15","detailName": "dname3"},{"detailId": "d4","detailMoney": "16","detailName": "dname4"}],"orderHead": {"orderId": "b1","orderMoney": "31","productName": "bname1"}}
]

    这个时候就有问题了，订单主体的最后一个是对的，15+16 =31 ，但是第一个怎么也变了？也就是说两个订单引用的是同一个对象，当其中一个发生改变的时候另外一个也发生了改变，此处可以在排序的时候对OrderHead进行复制重新计算,也可以在拆分的时候直接使用两个对象，我在此处使用的是 Spring 的 BeanUtils.copyProperties(Object source, Object target) throws BeansException 方法，具体split方法修改如下：

private void split(Order order, List<Order> result) {List<OrderDetail> orderDetails = order.getOrderDetails();Order order1 = new Order();Order order2 = new Order();List<OrderDetail> orderDetails1 = new ArrayList<>();List<OrderDetail> orderDetails2 = new ArrayList<>();for (OrderDetail orderDetail : orderDetails) {if (Double.valueOf(orderDetail.getDetailMoney()) >= 20) {orderDetails1.add(orderDetail);} else {orderDetails2.add(orderDetail);}}order1.setOrderDetails(orderDetails1);order2.setOrderDetails(orderDetails2);order1.setOrderHead(order.getOrderHead());OrderHead orderHeadCopy = new OrderHead();BeanUtils.copyProperties(order.getOrderHead(),orderHeadCopy);order2.setOrderHead(orderHeadCopy);result.add(order1);result.add(order2);
}

     修改完成之后得到的结果就是正确的了，具体细节可以使用debug查看，拆分之后的order可以看到引用的对象是同一个，此篇就不赘述，关于为什么不适用 clone 方法下篇文章讲述。