cqrs

Is it possible to do DDD and REST interface and language mapping?

由 喜你入骨 提交于 2019-12-03 06:22:31
问题 REST has a uniform interface constraint which is the following in a very zipped opinion based format. You have to use standards like HTTP, URI, MIME, etc... You have to use hyperlinks. You have to use RDF vocabs to annotate data and hyperlinks with semantics. You do all of these to decouple the client from the implementation details of the service. DDD with CQRS (or without it) is very similar as far as I understand. By CQRS you define an interface to interact with the domain model. This

Uniqueness validation when using CQRS and Event sourcing

由 China☆狼群 提交于 2019-12-03 03:49:12
问题 I'm trying to implement my own CQRS infrastructure with Event Sourcing to learn it better. As a sample project I'm implementing a blog engine, I know it might not be a perfect fit but I just want to work on something real. The problem I've come to now is validation. Every post have a shortUrl , and the shortUrl should be unique, but where should I put this validation in the domain? I know that I will have that validation before I even send the command by reading from my read store to check if

CQRS without Event Sourcing - what are the drawbacks?

由 强颜欢笑 提交于 2019-12-03 03:34:02
问题 Besides missing some of the benefits of Event Sourcing, are there any other drawbacks to adapting an existing architecture to CQRS without the Event Sourcing piece? I'm working on large application and the developers should be able to handle separating the existing architecture into Commands and Queries over the next few months, but asking them to also add in the Event Sourcing at this stage would be a HUGE problem from a resourcing perspective. Am I committing sacrilege by not including

Event Sourcing and Read Model generation

由 只愿长相守 提交于 2019-12-03 02:20:35
问题 Assuming Stack Overflow domain problem and the following definition of events: UserRegistered(UserId, Name, Email) UserNameChanged(UserId, Name) QuestionAsked(UserId, QuestionId, Title, Question) Assuming the following state of event store (in the order of appearance): 1) UserRegistered(1, "John", "john@gmail.com") 2) UserNameChanged(1, "SuperJohn") 3) UserNameChanged(1, "John007") 4) QuestionAsked(1, 1, "Help!", "Please!") Assuming the following denormalized read model for questions listing

CQRS - The query side

由 一个人想着一个人 提交于 2019-12-03 02:00:07
问题 A lot of the blogsphere articles related to CQRS (command query repsonsibility) seperation seem to imply that all screens/viewmodels are flat. e.g. Name, Age, Location Of Birth etc.. and thus the suggestion that implementation wise we stick them into fast read source etc.. single table per view mySQL etc.. and pull them out with something like primitive SqlDataReader, kick that nasty nhibernate ORM etc.. However, whilst I agree that domain models dont mapped well to most screens, many of the

Alternatives to many-to-many relationships with CQRS

由 久未见 提交于 2019-12-03 00:53:36
问题 How do we model classic many-to-many relationships with CQRS/DDD? I know that both DDD and CQRS implementations and solutions tend to be domain-specific, so it may be difficult to come up with a general answer to this question. However, let's assume we have the familiar relationship between Book and Author . This is a classic many-to-many relationship. To me, it seems most natural that Book and Author are two different Entities that each belong in their own Aggregate Root . Thus, explicitly

CQRS+ES项目解析-Equinox

由 我的未来我决定 提交于 2019-12-03 00:37:21
今天我们来分析另一个开源的CQRS+ES项目：Equinox。该项目可以在github上下载并直接本地运行，项目地址： https://github.com/EduardoPires/EquinoxProject ，该项目是基于 .net core 2.2的，开发语言、编码方式比Diary.CQRS更加新潮（ CQRS+ES项目解析-Diary.CQRS ），也更符合我们现在的开发习惯。 项目概览 首先通过github获取到项目源代码，打开项目文件，你会看到如下分层： Presentation：展示层，UI在该层实现 Services：WebApi在该层实现，同样隶属于UI Application：应用程序服务层，提供了对Domain层接口的封装，注重数据交换，DTO对象在该层定义 Domain：领域层，项目的核心部分，领域对象、领域服务在该层实现 Infra：基础设施层，项目的公共部分（数据访问）、切片（身份认证、消息发布、依赖注入）部分在该层实现 通过项目分层，我们已经对该项目有了一个大致的轮廓，当从Presentation、Services层接收到来自客户端的请求后，将会调用Application层的应用程序服务，应用程序服务将数据进行封装和转换，然后交给Domain层进行处理，Domain层则调用Infra相关的方法完成持久化、消息发布等功能。 Domain层

Value Objects in CQRS - where to use

由 痴心易碎 提交于 2019-12-03 00:33:28
问题 Let's say we have CQRS-inspired architecture, with components such as Commands, Domain Model, Domain Events, Read Model DTOs. Of course, we can use Value Objects in our Domain Model. My question is, should they also be used in: Commands Events DTOs I haven't seen any examples where Value Objects (VO) are used in the components mentioned above. Instead, primitive types are used. Maybe it's just the simplistic examples. After all, my understanding of VOs use in DDD is that they act as a glue

Passing CQRS commands directly to Domain objects

由 不羁岁月 提交于 2019-12-03 00:22:13
~TLDR: I'm implementing a CQRS + DDD solution for one of my larger projects, and, I'm wondering if there is any real reason that my command handlers can't directly dispatch the command objects to my aggregates, in a small handful of cases, where the command object is data rich? I can't find any specific reason why this would be any kind of an anti-pattern, and I can't find any opinions that go into great detail about this type of design. Background: I have implemented CQRS systems before, and I have implemented DDD applications, but never CQRS + DDD in a proper Eric Evans style domain driven

云时代架构阅读笔记十六――架构设计思维（二）

由 匿名 (未验证) 提交于 2019-12-02 23:45:01
架构的演变： 1、单体架构：Web应用程序发展的早期，在开发服务端企业应用时，应用需要支持各种不同类型的客户端，比如桌面浏览器、移动浏览器以及原生移动应用。应用还需要向第三方提供可访问的API，并通过Web Service或者消息代理与其它应用实现集成。大部分web工程是将所有的功能模块(service side)打包到一起并放在一个web容器中运行，很多企业的Java应用程序打包为war包。应用通过执行业务逻辑、访问数据库、与其它系统交换信息、并返回一条HTML/JSON/XML响应，来处理请求（HTTP请求与消息）。 2、SOA架构： SOA架构，是一种粗粒度、开放式、松耦合的服务结构，要求软件产品在开发过程中，按照相关的标准或协议，进行分层开发。通过这种分层设计或架构体系可以使软件产品变得更加弹性和灵活，且尽可能的与第三方软件产品互补兼容，以达到快速扩展，满足或响应市场或客户需求的多样化、多变性。 3、微服务架构：微服务是一种用于构建应用的架构方案。微服务架构有别于更为传统的单体式方案，可将应用拆分成多个核心功能。每个功能都被称为一项服务，可以单独构建和部署，这意味着各项服务在工作（和出现故障）时不会相互影响。是应用的各项核心功能，而且这些服务均可独立运行。但是，微服务架构不只是应用核心功能间的这种松散耦合，它还涉及重组开发团队、涉及如何进行服务间通信以应对不可避免的故障
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