DDD-如何设计不同有界上下文之间的关联 [英] DDD - How to design associations between different bounded contexts

问题描述

我已经设置了一个域项目，该项目正在填充ORM。该域包含不同的聚合，每个聚合都有自己的根对象。
我的问题是，应该如何对待跨越总边界的属性？

• 这些属性是否应该简单地忽略边界，以便


• 或者，是否应该没有从上下文A到B的直接链接，并且上下文A中的对象是否具有 int ContextBId属性可用于通过B聚合根从B获取域对象？


• 或...

示例：

上下文A =用户

上下文B =游戏

在 Users 上下文中，有一个对象 UserOwnedGames 。该对象具有属性 User ，该属性是对相同 Users 上下文中的对象的引用。该对象还具有 Game 的属性，该属性显然不在用户中，而在 Games 上下文中。 / p>

这种关系的样子（或应该怎样？）？在数据库中很明显（例如2个外键），但是代码应该是什么样子？

解决方案

听起来像您的 User 上下文也需要一个 Game 实体。但是请注意，这不一定是 Game 实体，它是 Game 上下文的根。这两个有界上下文对于 Game 是什么以及它具有什么属性可能有不同的想法。只有身份将两个游戏对象绑定在一起。

 用户上下文
 {
根用户总数
 {
身份； 
名称； 
 OwnedGames：游戏价值实体列表
} 
 
价值实体游戏
 {
 Identity; 
名称； 
} 
} 
 
游戏上下文
 {
总根游戏
 {
身份； 
名称； 
所有者：用户值实体
 HighScore：int 
 TimesPlayed：int 
 ...大量与用户上下文无关的其他属性
} 
 
价值实体用户
 {
身份； 
名称； 
 //没有OwnedGames属性，在这种情况下，我们不在乎用户拥有哪些其他游戏。 
} 
} 
  

I have setup a domain project which is being populated with an ORM. The domain contains of different aggregates each with its own root object. My question is how properties that cross the aggregate boundries should be treated?

• Should these properties simply ignore the boundries so that a domain object in bounded context A has a reference to an object in context B?
• Or, should there be no direct link from context A to B and does the object in context A have an "int ContextBId" property that can be used to get the domain object from B through the B aggregate root?
• Or ...

An example:
Context A = Users
Context B = Games

Inside the Users context there is an object UserOwnedGames. This object has a property User which is a reference to an object in the same Users context. The object also has a property to a Game which is obviously not in the Users but rather in the Games context.

How would (or should?) this relation look like? It's clear in the database (ie 2 foreign keys) but what should the code look like?

解决方案

It sounds like your User context also needs a Game entity. Note however that this is not necessarily the same Game entity which is the root of the Game context. These two bounded contexts may have different ideas of what a Game is, and what properties it has. Only the identity ties the two Game objects together.

User Context
{
    Aggregate Root User
    {
        Identity;
        Name;
        OwnedGames : List of Game value entities
    }

    Value Entity Game
    {
        Identity;
        Name;
    }
}

Game Context
{
    Aggregate Root Game
    {
        Identity;
        Name;
        Owner : User value entity
        HighScore : int
        TimesPlayed : int
        ... A whole bunch of other properties which are not relevant in the User context
    }

    Value Entity User
    {
        Identity;
        Name;
        // No OwnedGames property, in this context we don't care about what other games the user owns.
    }
}

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