I am using ASP.NET MVC in my application. I have divided my application into three layer architecture. 1) Data Access Layer (using Entity Framework), 2) Application/Business Layer, 3)Presentation Layer (ASP.NET MVC).
Because I am using MVC framework on my presentation layer, I am confused about the business logic. I need to know where do I put my business logic in MVC pattern. In other words we can say from where I need to call my middle layer. From the Models or from the Controllers?
If I call my business logic from Controller then It seem like the Models are useless. Other wise if I call business logic from the model then it seems like unnecessary bidden on the system because Business Object maps with model and then model is passed to the Controller. Model does exactly what DTO is doing.
Any help will be appreciated
ASP.NET MVC layer or tier doesn't contains neither business logic nor business model. M in MVC stands for UI model, not the model of your application core and MVC (as well as other MV* patterns) is generally pattern for separating UI concerns. You should send messages (call) your Business Layer (BL) from Controllers, aggregate data, create or map it results into UI model and pass it to view. Your UI model should know nothing of BL model - this distinction makes loosely coupled layers of your application.
In other words we can say from where I need to call my middle layer.
From the Models or from the Controllers?
Definitely from Controllers. You inject dependencies to it and call them from your Action methods. ASP.NET MVC provide lots of mechanisms of injection dependencies into controllers and integrates nicely with NInject, StructureMap and some other IoC containers.
Dependencies between components in MVC is given below
Picture is takes from Martin's Fowler article on GUI Architecture, which by the way, very nice reading regarding MVC and MVP.
Also, Pluralsight has set of videos on Software Practices, which covers Design Patterns. I've learned a lot from their definition of MVVM and MVP.
Reading this materials should increase your understanding not only on patterns itself, but also in how they fit into application environment and interact with it.
This is purely design/architecture decision you have to make based on your requirements.
If you want to scale up your application to support other services/applications, it is advised not to write any business logic in Controller/Model. You could write it in business/application layer. This will help you to scale up your architecture in future. Say if you want to create restful service for you mobile application, you could just write services as wrapper to re-use existing business/application layer.
Also just have a look at Domain Driven Design, Eric Evans book is worth reading.
http://dddsample.sourceforge.net/architecture.html
Related
can you give me some hit or give me explanation how to create Enterprise App in .net, and how projects type use or how should be structure of this projects? I newbie in EE and I read about it, but for me is the best explanation on real world example. My idea about EE solution structure in .net is that:
Data Tier (project type => class library)
database access classes
some mappers (I am not sure if I could use data mapper pattern or else? Is good idea?)
Bussiness Tier (project type => class library)
entities which wil lbe mapped in data mapper in Data Tier
and some application logic
service tier (I am not sure if it should be individual tier, or subtier of bussiness tier - I want to use WCF)
Client (project type => WebForms / Android / WPF / ....)
will be communicate with bussiness tier over WCF
Is my idea good? I will be gratefull for any explanation or hint how patterns could I use with respect my low knowledge. I have requirements to use 2-3 patterns, becouse is school project. Thanks for answers
A implementation I have found quite useful is:
Data Access Layer:
Entity Framework: Unit of Work
Repository Pattern
Business Layer
This layer maps entities and db calls to DTOs
Presentation Layer
Here you present your DTOS using MV? or any other model
There you are using at least 4 design patterns.
For the data layer I would go with repository pattern and unit of work pattern. This is really good way to abstract data layer and create testable code which can be easily unit tested.
Business layer it depends, by DDD business should be encapsulated inside rich data model. Anemic data model is considered as anti pattern. But personally rich model can lead to the ruin of the separation of concern paradigm. Sometimes it is useful to have anemic data model and business layer on top of that model. Like handlers where every handler does exactly one action...
On top of business layer is usually application layer which expose interface to the outside, to your clients. It should be really thin without any business logic in it. Maybe Restful API which will enable you to connect various clients like Android, wpf, Javascript...
To give you a quick overview of my application architecture, I have the following layers in my application:
Domain Model - Models the problem domain and business rules.
Service Model - Models the service contract consumed by the application.
Data Access Layer - Persistence of domain models, in this case using EF.
Services - Implementations of the service model.
Website - MVC web application.
Web API - RESTful web service API.
Now the problem is that the Web API came later; the MVC web application was the first thing that was built on top of the architecture.
I find myself having to replicate business logic and ViewModels (MVC) and Messages (Web API)...According to the DRY principle, I shouldn't be doing this, so the natural solution is to push the business logic into its own layer which is independent of the application layers.
But...this means that the business logic layer needs it's own set of models which sit between the application layer and the business logic layer. In this respect, it would not be applicable to use domain models, since these really shouldn't ever hit the application layer.
So in short, I'm looking for an industry accepted standard for business logic modelling. Is there an accepted standard for how this should work, and if so, what type of model (i.e. it's not a domain model, and it's not a view model) belongs to the business logic layer?
You have stumbled upon a contested point of discussion. I myself have struggled with this for a long time.
Object bigots will argue that you shouldn't even have a service layer. Your domain model could then be directly consumed which would eliminate the duplication of logic. Granted, those were the good old days of software modeling. With the advent of the web, apis and SOAs, we are forced to look at alternative ways of modeling our software. Enter Anemic Domain models.
Anemic Domain models essentially consist of light weight objects that resemble DTOs more than anything, with underlying services that do the heavy lifting.
The architecture you have described above seems to be a hybrid design. I am guessing by now you must have run into the issue of mapping EF classes to domain objects, which creates yet another layer of objects, unless you use POCOs, in which case you run into namespace issues and what not.
Anyways, I don't think there is an industry standard. What I can tell you is that I have seen a few patterns emerge here and there leaning towards Anemic Domain Models and it's not hard to see why. In disconnected environments (e.g. web, API), complex objects don't work very well, hence the affluence of services.
Since you have layered your application nicely and do not wish to expose your domain model objects, I would suggest using Anemic Models in your service implementations. These would essentially function as DTO objects that can be reused and serialized if the need be, but can also implement basic logic that may even map back to functionality implemented in the services.
On a final note, there is no one-size-fits-all. Use the right tool for the job. Patterns are meant to be guidelines, not step-by-step instructions, so make sure you feel free to tweak them in order to fit your particular needs while retaining the general idea.
You can read more about Anemic Domain Models here:
https://en.wikipedia.org/wiki/Anemic_domain_model
Make sure to check out Martin Fowler's objections to Anemic Domain Models as well:
http://www.martinfowler.com/bliki/AnemicDomainModel.html
In my n-tier .Net Application I got next layers:
Data Access Layer (EF)
Business Layer (Validation & Business Logic)
Presentation Layers (1 MVC Controller and many API Controllers)
I found, that my Business Services only validate business objects, call CRUD DAO methods and return results to Api Controllers.
So, I doubt: may be Web Api Controllers should be used as Business Services?
Interesting, just answered a similar question...
So I woudn't do it I were you.
Here's just a few disadvatages of the approach from the top of my head:
Performance - a redundant HTTP roundtrip in Web MVC project.
Separation of concerns - most of the time the functionality provided
by API differs greatly form UI for the same project/application. You
might want to limit the API to a few methods with a strict contract.
In case you want Web API to be a layer between Web MVC and your DAL
you will have to expose all functionality you need for UI as well.
Also you might want to have different authorization and
authentication mechanisms. Very often API exceptions handling is
also different as well as input validation.
Maintanance - everytime you need to make a change required for UI
only you have to make sure it doesn't brake your API clients. Also
API versioning is a very important topic and mixing it with most UI
changes makes this process even more difficult.
Probably for now you application is not that complex but from the design perspective your solution is much more flexible now than it will be if you decide to put Web API between your UI and DAL layers.
N-Tier applications and multi-layer are not popular among the new wave of developers. Keep in mind, that just because something is not popular, among a group, does not mean that it does not have merit.
Pros of MVC:
Separation of Concerns
Unit Testing
Does a multi-layer MVC application using a Web.API have merit:
I know this will be met with some discontent and disagreement. However, my concern is that single purpose application developers are not giving consideration to enterprise development. Enterprise development, load balancing, manageable code maintenance, and true Separation of Concerns are only possible with multi-layer applications that can easily lend themselves to N-tier.
Many developers are operating in environments that demand that they design and implement data structures in SQL, create and maintain models and CRUD functionality, develop controllers and design good looking and friendly views. The MVC model utilizing Entity Framework makes this a manageable task for these small to moderate platform developers.
In the Enterprise, separating the Business and Data Access layers from the User Interface makes real good sense. Right now MVC is a popular and very functional platform for efficient and usable User Interface development. What will be the UI platform in ten years? Separating the UI from the other layers gives more life to the work spent developing the business logic. Not to mention, that it allows for accessing data on multiple platforms today.
Multi-layer MVC using Web.API has these advantages:
True Separation of Concerns
Supports Unit Testing
Makes the Business logic and Data Access logic more scalable and reusable than MVC alone.
Supports data processes without page refresh. (REST)
CONS:
- Does not easily support use of Entity Framework. (Which is not ready for the enterprise yet anyway)
You could have your code as part as your model, and that would even be considered as good separation of concerns since MVC is build for that.
But what my preferred thing to do is keep logic in a Business Layer of it's own. The reason for that is, I think, better separation of concerns. I like using IoC, so there might be different configurations that I route thought different running solutions. Or, I might have another UI/API/Project that uses the same logic layer.
As for the overhead, it has a little overhead, but I think worth the trouble comparing to the actual overhead in code it creates.
I agree with others here, looking into using strongly typed views, the controllers would only create an instance of the viewmodel and send it on to the view. The view model then is the intermediary to the data services layer. I personally create all my entities using EF in a different project just to separate function. The view model can either call EF directly or you can add another layer of pre-canned EF queries which the Viewmodel uses just to populate the view collections. This would look like this:
[View]-[Controller]-[Viewmodel]-[Optional repository and interface to EF]---[EF]
In the interface to EF you would catch all DB errors when trying to get information and post back to the view according to your design.
The beauty of strongly typed views is that they post back and forth from the View and can contain methods which you can call at will. Because they are a pseudo model for the view, they can also have properties specific to the view which may be used at the business layer. I pass view models around quite a bit were warranted. (After all they are just a pointer)...
You can implement business logic/validation/calucations in the actual model/entity classes rather than ApiControllers, otherwise you will end up with so much code in your controller which is not really a good thing.
Also you can use DataAnnotations Attributes to perform your validation which sits outside of your controller. for.e.g. http://msdn.microsoft.com/en-us/library/ee256141(v=vs.100).aspx
I am new to asp.net mvc. I want to divide presentation layer with logic layer. I know it is already done in asp.net mvc but I want to have presentation layer on another machine. I don't know if this what I want to do, is possible, but just wanna ask. I want something like this: User enters address 123.123.123.123/Home then that request is redirected to presentation layer. Presentation layer is then asking "Logic Server" for data(from database or smthing) and logic server returns it back to presentation layer which presents the page to the client.
My overall goal is to make framework which allows us to do this easily.
And my questions:
1. Is it worth doing it?
2. Is it possible with asp.net mvc ?
3. Is there anything like this?
I wanna also extend that framework to work independent from technology. And the presentation layer would be a "connector"
You can do this by having some kind of Service Oriented Architecture. In your MVC app you have a services layer, this could talk to a WCF service or something similar on your network. Your WCF service would then talk to another machine for data storage, do the required business logic and return simple DTO's.
Is it worth doing? This depends on you. Is there a good reason to do this? It shouldn't be that hard, and if you write your MVC app correctly the services layer will abstract away the fact that the service is on another machine or the same machine so you have some flexibility to change your mind later.
Is it possible? Yup
Is there anything like this? I'm sure there are plenty of people out there who are doing/have done what I have described
Quite strange architecture.
You can indeed use SOA. It has many advantages and it's well studied and supported.
However, I wouldn't use SOA for the presentation layer (and I don't remember to have seen that never).
You'd normally have the business logic in a layer, and expose it as Web Services (that's SOA), and all the presentation (in this case creating MVC view models, and returning the rendered views to the browser) in the same application. (See note at the bottom)
It has no sense to separate the Presentation in a SOA layer, because you cannot reuse it for anything else. I.e. you cannot use that presentation layer for a windows application, or to use it for a java web application.
However, if your business logic is exposed in a SOA layer, then you can use it with any kind of UI you want: windows forms, WPF, or even a Java Web Application.
Apart form this there is a tigh knot between routes, and controllers in MVC. You cannot easily achive what you want to do. However, you can easily make an MVC presentation layer (routes, controllers and viewws), which uses the business layer exposed as SOA from your controllers. That's much more natural.
Is it possible: of course, but non-standard and har to do.
Is it worth: No it isn't. Your canot reuse it with a different techonlogy. Which is the advantage?
Is something like this: neve seen it!
NOTE: having a single app doesn't mean having a single layer. But you don't need to separate them in different applications or SOA layers. If you use MVC correctly you'll have a very clear separation between Views (which render the result for the browser) and controllers (which prepare the View Models for rendering the Views) and the Business layer (which can be in a different app, exposed as SOA services, and consumed from this controllers). In fact, it's hardly impossible to make a bad use of MVC if you have into account that you need View Models, which are objects specifically created for the view to be rendered, instead of using directly the business entities.
For example a vie model can have a customer's data to edit it, but probably will have several lists of options for populating drop down lists. If you don't use view models, you'll soon have problems.
My question is in regard to the first "M" in MVVM, the model. I see a ton of variations on how to implement the model. Some are just POCO's with no business logic and no persistence logic, and others contain one or both.
Right now, in our application, we have a decent separation between models, views, and view-models. This is our current solution structure (its a WPF prism application):
Infrastructure
Module A
ViewModels
Views
Module B
ViewModels
Views
Models (shared amongst modules, which is why its in its own class library)
Services
DataAccess (possibly utilizing dapper-dot-net)
Shell (main WPF project)
We now need to figure out how to perform our CRUD against the database and keep our models updated. I like the idea of keeping the models pretty bare-bones and having a "Services" class library that contains our business logic and performs a unit of work pattern against our data access classes. Are there any known issues with keeping the models dumb and ignorant of business logic / data access? Is this pretty uncommon to do in MVVM?
I wonder if I'm limiting myself or making things more complex than they need to be by not placing some logic in the models, for example, loading a model from within its ctor given an argument. As a note, this will be a large application.
Our application will have to persist models to multiple databases. We're using Unity as our dependency injection container for our services. How would you recommend I tell the service which data connection to use? Ctor, per function, etc?
Kinda looking for someone who built a similar structure, and what their experiences were / recommendations are.
In my view, MVVM models just 'represent' the data and should therefore not have any logic, CRUD or otherwise embedded. You already have the Data Access Layer so it is perfectly normal to write your CRUD code there and to use DI to access this CRUD code from your models.
The "beauty" of MVVM is that it is open to interpretation so I'm sure someone else would argue that model IS the data and it can containt CRUD logic...
I have all my CRUD operations in my DAL and am yet to see the downside of that approach...