I have the following design :
My Design
My Design http://s15.postimg.org/3zha8rzqh/Design_Idea.png
I will have a class called 'ProductDTO' in my service layer (the left service).
When the 'Update Product ( ProductDTO )' operation contract is called - it should call the 'Update Product' function in the Business Logic Layer.
In the database (the 'Data Access Layer') there is an entity called 'Product', and because I use LINQ-To-Entities I will also have a class there called 'Product'.
My question is - where do I translate from 'ProductDTO' to 'Product' ?
Should I have a 'Translate_ProductDTO_To_Product' function in the service layer ?
It seems the most logic answer, because that is the only layer that knows what 'ProductDTO' is.
But this means that the service layer will also have to know what 'Product' is, and thus will have to reference the data access layer assemblies.
Is this correct ?
I thought that the service layer should only reference the business logic layer, and that the business logic layer should only reference the data access layer, and that the service layer should know nothing about the DAL.
It seems your confusion may stem from assuming the Product class in your data layer is actually the Product entity. Generally in domain driver design, your business entities live-in/are the business logic layer. Usually these class are "ignorant" of persistence which is the responsibility of the data access layer (typically using an object-relational mapper framework).
In practice, your service will require references to both to the domain model (business layer) and the data access layer to perform useful work. Both the WCF service code and the data access layer should depend on the domain model but the domain model should not have dependencies on either the data access layer or the WCF service code.
Map the DTO to your domain entities in your service layer. Your service layer needs to know about DTOs and the entities it is mapping to (and from). I strongly advise you use a tool like AutoMapper to do the mapping rather than hand-crafting.
Your service layer should not reference your DA layer (or assembly). Your BL later will need to reference your DA layer to persist the entities.
Edit:
Your business entites probably should not be under a DA namespace. If you are using an ORM tool to generate them, make sure you put any DDD logic in the other half of a partial class.
Related
We are creating rest api's with Spring Boot. We have three layers in our project(Repository, Service and Controller).
Lets say I have GetUser api in my controller that return UserDTO object.
#GetMapping
public UserDTO getUser() {
return userService.getUser();
}
Whether userService.getUser() returns UserDTO object or it returns User object and it is converted to UserDTO object in the controller? Which one is better way?
Shortly, domain object to DTO object conversion, should be done in service layer or controller layer?
I think there is no "better way" for converting your domain objects to your DTO objects, it's a matter of taste. In my projects I convert the domain objects to the DTO in the service layer as part of my "business logic". So you reduce the accessability of your domain objects only to your service layer. Furthermore I want to reduce the "logic" inside my controllers as they are part of the application layer.
PS: If you are looking for several ways to convert your domain objects to your DTOs have look at one of my latest Stackoverflow questions (How to properly convert domain entities to DTOs while considering scalability & testability)
It depends on application needs and architecture. Idea is to keep dto conversion at edge. It is generally prefer to have dto and domain conversion at the controller level. If you want to keep services/business logic independent of consumer, then it is always better to have at api level. This becomes more clear if your service has been consumed by more than one consumer.
In my experience, the conversion should be on the Controller layer. This gives an advantage that able to reuse other service methods with the return object is the origin.
This point may be important sometimes because the DTO object often reduce fields from the origin object. Therefore, we need more code to get these reduced fields, making our code ugly and duplicated.
I know that it would be moving logic to the controller layer, but it is a tradeoff.
Here is what I do in general:
My service layer takes dto as an argument.
I do the conversion at the service layer, because I might need to apply some business logic when converting.
But my service layer always returns entity. And I do the conversion at the controller level. This makes my service is clean and independent of the consumer. It may happen that my service might be consumed by another service and need entity not the dto.
In summary:
Dto —> Entity (Service layer)
Entity —> Dto (Controller layer)
I have asp.net mvc 2 application. i have confusion creating DTO and domain entities.
MVC Controller Integration points:
1) third party WCF
2) DB Layer
WCF is returning Persons information of a particular company and some information about company.
I have generated proxy of WCF and written a service wrapper on the proxy.
Service wrapper is talking to WCF and Mapping the results to DTO clas ContactsDTO
Service layer is in different project.
Following are my domain classes
Company
Person
DTO class
//it contains
class ContactsDTO
{
Person person, Company[] company
}
Controller action calls the wrapper with companyID and get the object of DTO class.
and update the company information from dto. it updates the company information in Session and pass the Company[]array to some other operations.
DB interaction:
Now depending upon some business logic, i have to insert Person-ids and company id along with some other information in Database.
for this i have created another
class DBDTO
{
Person person, Company[] company, OtherInfo otherInfo[]
}
this DBDTO is prepared and passed to DB Layer(which is using Linq to sql).
Questions
Is it write way to do. Any improvement in DTO interaction? What all
changes i can do to improve the overall architecture
Another alternative to DB-bound objects being translated to DTOs (which takes time) is to use POCO (Plain Old CLR Objects) and use them directly as your Domain Model, objects that can be stored in the DB and objects that are communicated to Controllers for visualization.
This can get you started: Working with POCO Entities
This approach has several advantages
Your POCO entities are independent of the underlying DB implementation
Your POCO entities can be unit-tested without presence of a Database
You can easily serialize them into a service response (if you are building an API) using DataContractSerializer or DataContractJsonSerializer
I agree with Algirdas to differentiate models because of different responsibilities.
By the way: MVC is not a layer concept. It's a concept of three responsibilities and their collaboration. Although it is often (mis)used for layering you will encounter problems with SRP if you only separate your application layers applying "MVC". If you have MVC per layer then you go well.
After all if it is a small application you maybe never reach the critical mass to have problems with the architecture.
I have business layer and UI layer in separate projects within a same solution. What i need is ,connect this UI with business layer which coded in c#. UI created using MVC3 Razor.
What i should use as model in MVC application? am i need to create Service reference to business layer to generate some proxy?
then can i use those proxy as a model? please help me..
if you can provide me some tutorials
i tried this but no more idea with MVC :
http://www.dotnetfunda.com/articles/article816-understanding-the-basics-of-wcf-service-.aspx
Unless your project (or architect) demands that all methods of your app access a services layer, I would try and avoid using WCF unnecessarily (think of it - it means that all of your data between web server and back end goes over the wire, which has implications such as performance, serialization of data, and also potentially limits the lifespan of database connections and transactions, which can deprive such as lazy loading).
If you concur, the suggestion would be to ensure all accessible interfaces in your business layer are exposed on an interface, and then consume or inject the BLL interface directly into your controller.
You need to be careful about the word "Model" in MVC - ASP NET MVC encourages ViewModels, which are specific to the presentation tier and passed between Views and Controllers, as opposed to "Entities" which represent the more logical domain model as used by business logic and which can be tied to data persistence using an ORM such as EF or NHibernate. The MVC project template lumps everything which isn't View or Controller into "Model" which isn't necessary very helpful.
However, if you do choose to access your BLL via a WCF Services layer you still have some design decisions to make:
Choose whether you share the back end entities on the client side, or do you instead use proxied entities.
Choose whether you consume / inject the WCF service proxies directly in your controller, or do you create another facade layer (e.g. CAB calls these ServiceAgents). The latter would make sense if there are separate teams or vendors building the SOA side vs the Client side in order to accomodate changes to interfaces.
I have a set of custom entities which reflect the business representation of data. Then I also have a set of entities that map 1-to-1 to the database that represent the storage of the data. My business layer converts between the 2 types and performs any other logic needed. I only expose the custom objects through my service interface.
From what I can tell I cannot use WCF Data Services. Data services
need to be bound directly to a db source (or some slight abstraction of the direct db connection) and,
that results in using the data entities.
Correct me if I'm wrong, but I can't see any way to use WCF Data Services and its built-in queryability with custom entities while using my business layer.
I do not necessarily agree with that. If you look at the Architecture Overview in http://msdn.microsoft.com/en-us/library/cc668794.aspx you see two other options next to the EF / DB connectivity. You can have Data Service Providers that just take an alternative (your custom) information model made up of queryable CLR classes and expose them using WCF data services.
So if you create your Business Layer using this approach, your custom entities can just as easy be exposed with WCF data services.
Hi
we have used the WCF service in my project. In our application the following layers are exists,
UI (aspx file), and code behind.
(Customer.aspx)
UI entity Model (CustomerModel.cs)
which is properties of the customer
details.
UI layer calls the Business Façade class with the CustomerModel object.
In Business façade I have referenced the WCF service.
Convert the CustomerModel to CustomerContract.
Call the CustomerService from business façade.
In the service, I have convert CustomerContract into CustomerBO and call the CustomerBO class.
In the CustomerBO class,I have initialized the provider object and call the customer Provider class.
In Provider class, I have access the Database and send data from 8 to 1 layer.
I don't know which design pattern is using in our project. Can anybody help on this to identify design pattern.
Thanks
This is not about design pattern but about architecture. Your architecture itself is not bad but it is really complex so unless you are creating very big project this architecture can be overkill. Moreover your naming of different layers is not correct. What you call BusinessFacade is usually called ServiceAgent. BusinessFacade should be placed on service site and wrapped by WCF service. Usual responsibility of BusinessFacade is to aggregate several business operations into single calls = create less granular API which can be easily and effectively exposed for remote calls.