Questions tagged [domain-driven-design]
Domain-driven design (DDD) is an approach to develop software for complex needs by connecting the implementation to an evolving model.
155
questions
9
votes
2
answers
4k
views
Zero argument constructors and Always Valid entities
I have done a lot of reading recently about Always Valid domain entities. I have come to believe that in order to ensure the entities are always valid I need to:
1) Remove primitive obsession and ...
- 7,021
51
votes
4
answers
24k
views
Where we should put validation for domain model
I still looking best practice for domain model validation. Is that good to put the validation in constructor of domain model ? my domain model validation example as follows:
public class Order
{
...
- 623
29
votes
9
answers
10k
views
When is primitive obsession not a code smell?
I have read plenty of articles recently that describe primitive obsession as a code smell.
There are two benefits of avoiding primitive obsession:
It makes the domain model more explicit. For ...
- 7,021
225
votes
11
answers
30k
views
Why do we need so many classes in design patterns?
I am junior developer among seniors and am struggling a lot with understanding their thinking, reasoning.
I am reading Domain-Driven Design (DDD) and can't understand why we need to create so many ...
- 1,767
48
votes
2
answers
19k
views
How do you handle shared concepts in a microservice architecture?
I am researching architectural patterns for an application I'm developing and a microservice approach seems like it would be a good choice but I am not sure how to handle interactions between the ...
- 598
43
votes
3
answers
20k
views
What, in reference to DDD, is a bounded context?
When working through the book "Implementing Domain Driven Design" by Vaughn Vernon, I have been unable to gain a good grasp on what a bounded context actually is.
The book defines a bounded context ...
- 6,437
8
votes
3
answers
7k
views
What is the "best" way to approach validation from the perspective of a DDD purist?
I recently asked this question.
I am trying to decide where to put the validation in a DDD app. I believe it should be done at every layer.
I am now concentrating on the Domain model. I was ...
- 7,021
17
votes
5
answers
10k
views
Is it bad practice for services to share a database in SOA?
I have recently been reading Hohpe and Woolf's Enterprise Integration Patterns, some of Thomas Erl's books on SOA and watching various videos and podcasts by Udi Dahan et al. on CQRS and Event Driven ...
- 3,154
13
votes
2
answers
4k
views
Where to validate domain model rules that depend on database content?
I'm working on a system that allows Administrators to define Forms that contain Fields. The defined Forms are then used to enter data to the system. Sometimes the Forms are filled by a human via a GUI,...
- 233
12
votes
4
answers
2k
views
How to clearly define boundaries of a bounded context
After a month or so of reading and researching DDD, I decided to start my own project and created DDD with these bounded contexts>
Clients
Products
Orders
Billing
Each bounded context has rest API ...
- 795
8
votes
4
answers
13k
views
ID properties on Domain objects in DDD
In my domain I have an Account object.
e.g.
class Account
{
public string Number;
public string SortCode;
}
Within the context of DDD, should this account object have an ID property? The ID ...
- 714
5
votes
1
answer
3k
views
DDD with web api, validation in domain or application layer?
I saw a lot of discussion, but I don't know how to do it in a real world.
I understand that validation duplication in the client and server is needed.
But how to elegantly validate in server and ...
- 61
85
votes
7
answers
103k
views
Application layer vs domain layer?
I am reading Domain-Driven Design by Evans and I am at the part discussing the layered architecture. I just realized that application and domain layers are different and should be separate. In the ...
- 6,042
44
votes
8
answers
7k
views
Can a system be 100% Data Driven?
My new boss has been working on this project for many years. I've only been here a few weeks, but I am not sure it's possible. He would like to design a system that is "100% data driven".
So if we ...
- 559
36
votes
3
answers
26k
views
Implementing DDD: users and permissions
I am working on a small application trying to grasp the principles of domain-driven design. If successful, this might be a pilot for a larger project. I'm trying to follow the book "Implementing ...
- 473
30
votes
2
answers
9k
views
Best practices for serialization of DDD aggregates
According to DDD domain logic should not be polluted with technical concerns like serialization, object-relational mapping, etc.
So how do you serialize or map the aggregates' state without publicly ...
- 519
27
votes
3
answers
12k
views
What is Domain Driven Development in practical terms? [closed]
I heard about Domain Driven Development from a developer in the area. He talked it up like it was just about the silver bullet to changing requirements.
I read the wiki. Still not too clear. What ...
- 11.1k
19
votes
2
answers
10k
views
Is there an elegant way to check unique constraints on domain object attributes without moving business logic into service layer?
I have been adapting domain-driven design for about 8 years now and even after all these years, there is still one thing, that has been bugging me. That is checking for a unique record in data storage ...
- 10.2k
18
votes
2
answers
8k
views
DDD Bounded Contexts & Domains?
I've been working in a relatively complex application with 10's of database tables (Aggregates, Entities/Value Objects) and applying DDD. At this point it appears to be basically DDD-Lite meaning that ...
- 377
15
votes
5
answers
16k
views
Find the DDD Aggregate Root
Let's play everyone's favorite game, find the Aggregrate Root. Let's use the canonical Customer/Order/OrderLines/Product problem domain. Traditionally, Customer, order, and product are the AR's with ...
- 257
15
votes
3
answers
15k
views
How to work with large aggregate roots?
I'm learning DDD and yet I have more questions than answers.
Let's consider a model of a directory containing enormous number of files.
Here is how I see it:
Directory is an Aggregate root.
This ...
- 1,640
15
votes
2
answers
12k
views
Should CQRS Command perform a Query?
I have Customer, Order, and Product Aggregate Roots... When the order is created, it takes in a Customer and a List<Sales.Items>. It looks something like:
public class Order
{
public static ...
- 1,199
13
votes
3
answers
5k
views
Validation and authorization in layered architecture
I know you are thinking (or maybe yelling), "not another question asking where validation belongs in a layered architecture?!?" Well, yes, but hopefully this will be a little bit of a different take ...
- 2,885
12
votes
1
answer
982
views
Do ORM POCOs replace domain entities?
This is somewhat similar to this question but more broad.
In general, with ORMs like EF 4.1 supporting POCOs, does it now make sense to have your domain entities be the objects that are persisted to ...
- 300
12
votes
3
answers
5k
views
Confusion about the meaning of the word aggregate in domain driven design
In a discussion about domain driven design I have learned the different people seem to think of different things when using the word aggregate. The main difficulty is that some people use the word ...
- 669
11
votes
4
answers
9k
views
What is a value object in domain-driven design?
I have an entity and I've realised that there is a group of properties that work together. So, I moved them to a value object (together with their behavior) and now I have a reference from my entity ...
- 1,289
10
votes
2
answers
3k
views
Where should I put Validation Logic when using CQRS?
I asked this question a while ago: What is the "best" way to apprach validation from the perspective of a DDD purist?
At the time I decided to put the validation logic inside the domain ...
- 7,021
8
votes
4
answers
5k
views
In DDD, how do I persist an aggregate containing polymorphism
I've been developing applications according to the principles of DDD for a while now, and, as many, I often run into issues when it comes to persisting an aggregate.
One of the main advantages of DDD ...
- 388
6
votes
2
answers
3k
views
Should a Rich Domain Model have repositories injected in some situations?
Please see the code below, which I took from Jimmy Bogards wicked domain models:
public Offer AssignOffer(OfferType offerType, IOfferValueCalculator valueCalculator)
{
DateTime ...
- 7,021
6
votes
3
answers
6k
views
Is the builder pattern applicable in domain driven design?
I asked a question on StackOverflow regarding how to 'best' use the Builder pattern for constructing a Value Object which could be constructed with or without optional parameters.
One answer stated ...
- 365
6
votes
3
answers
6k
views
DDD + POCO does this makes sense?
DDD promotes rich domain models with behavior in it, POCO naked objects without any objects in it. Is it possible to have them both combined?
I have a Multi Layer Solution
Core - has POCO Entieties,...
- 305
4
votes
1
answer
2k
views
Recovering an anemic domain model into a multitier architecture
I have spent the past several days learning about domain driven design and attempting to apply it to a current project. I decomposed the problem domain into the canonical logical components: domain, ...
- 173
3
votes
1
answer
307
views
Where does complex, heavyweight validation logic go?
I've been struggling to figure out a clean way to validate things when objects have complex relationships and the validation requires expensive operations (e.g., making DB queries or other RPCs).
...
3
votes
1
answer
1k
views
Doubts about architectural pattern for customizable standard enterprise application [duplicate]
My company needs to build an application to be rolled out for a lot of clients. This software will have many modules and functionalities, but some of these will need specific adjustments for some ...
- 2,426
2
votes
1
answer
2k
views
Which Software Layer should hold Pagination Information?
Which layer should hold pagination information? (Page Size, Page Number), Eg say 100 products, 5 product per 20 pages.
User can type in API url layer.
api/Product?Page=1&Limit=2&ColumnSort=...
- 61
1
vote
2
answers
2k
views
Should I mock a Domain Service?
I am trying to decide whether to introduce mocks in my isolated Domain Model tests. I have a class method similar to this:
public Offer AssignOffer(OfferType offerType, IOfferValueCalculator ...
- 7,021
1
vote
1
answer
424
views
Have I understood the term Honeycomb correctly?
Following on from my previous question and the comments under the accepted answer: One Acceptance Test project per layer or one Acceptance Test project per Bounded Context
I have done a lot of ...
- 7,021
1
vote
3
answers
3k
views
Domain Driven Design in an Onion Architecture
I recently asked this question: Should the domain layer be dependent on NHibernate?
I have read a lot of questions today, where answerers state that the Domain Layer should only contain Business ...
- 7,021
101
votes
5
answers
15k
views
With all of these services, how can I not be anemic?
Where do we draw the line between delegation and encapsulation of business logic? It seems to me that the more we delegate, the more anemic we become. However, delegation also promotes reuse and the ...
- 2,885
96
votes
6
answers
136k
views
Difference between a service class and a Helper class [closed]
I would like to know what differentiates a Service class from a utility class or a helper class?
A class only with underlying methods calls the dao's is a service? Doesn't the usage of Helper ...
- 1,233
82
votes
4
answers
6k
views
Programming and Ubiquitous Language (DDD) in a non-English domain
I know there are some questions already here that are closely related to this subject but none of them take Ubiquitous Language as the starting point so I think that justifies this question.
For ...
- 1,135
60
votes
4
answers
45k
views
DDD repositories in application or domain service
I m studying DDD these days, and I m having some questions concerning how to manage repositories with DDD.
Actually, I have met two possibilies :
First one
The first way of manage services I've ...
- 1,481
56
votes
6
answers
25k
views
Are DDD Aggregates really a good idea in a Web Application?
I'm diving in to Domain Driven Design and some of the concepts i'm coming across make a lot of sense on the surface, but when I think about them more I have to wonder if that's really a good idea.
...
- 2,768
50
votes
11
answers
29k
views
Best practice or design patterns for retrieval of data for reporting and dashboards in a domain-rich application
First, I want to say this seems to be a neglected question/area, so if this question needs improvement, help me make this a great question that can benefit others! I'm looking for advice and help from ...
- 3,325
46
votes
4
answers
28k
views
In DDD, is validation application logic, or domain logic?
Suppose that we are modelling a form using DDD; the form may have certain kind of business rules associated with it - perhaps you will need to specify an income if you are not a student, and you are ...
- 939
43
votes
5
answers
56k
views
Is it good practice to use entity objects as data transfer objects?
I am wondering because if it is, why does Entity Framework not offer logic to create a new object with the same properties to transfer data between layers?
I use the entity objects that I generate ...
- 549
37
votes
5
answers
25k
views
Which layer do DDD Repositories belong to?
In his DDD book Evans promotes the idea of layered architecture, and in particular that the business logic should be confined to domain layer and separated from UI/persistence/other concerns. He also ...
- 1,209
37
votes
7
answers
10k
views
Do RESTful APIs tend to encourage anemic domain models?
I'm working on a project in which we are trying to apply both domain-driven design and REST to a service-oriented architecture. We aren't worrying about 100% REST compliance; it would probably be ...
- 1,810
35
votes
2
answers
22k
views
DDD: is it correct for a root aggregate to hold a reference to another root aggregate?
When following Domain-driven design (DDD), is it correct for a root aggregate to hold a reference to an internal entity that happens to be the root entity on a separate aggregate?
I believe this is ...
- 453
31
votes
2
answers
9k
views
Domain-Driven-Design - external dependencies in the Entity problem
I'd like to start Domain-Driven-Design, but there are several problems I'd like to solve before starting :)
Let's imagine I have a Groups and Users and when user wants to join a group, I'm calling ...
- 491