Both of them are based from mvc.
But in 3-tier architecture,storage layer is a separate layer,
while in symfony framework,database(storage) level is included in model layer.
Why are they different?
I would say that MVC is focused on user-interaction. It describes how to develop a rich and flexible system that reacts to user requests, but says nothing about what happens below controller layer.
It just says:
user sends a request;
dispatcher forwards request to appropriate controller;
controller retrieves models, but it's not specified HOW: using model's methods, using a DAO layer, using a Managers layer, whatever;
controller forwards to a view.
CakePHP also has model and data layer glued together, as many others. It's just a choice: this way you have less layers and less code, but in case you change your mind you'll have to modify all your code, directly in the models.
Related
I am new in MVC and little confuse and want to ask about differences and purposes of both.
MVC model and Business Logic layer (BLL) in tier Architecture.
What is the purpose and need to use BLL? some say they exchange the data between Presentation layer and data access layer. except these elaborate the BLL purpose.
So, we create properties in both MVC Model and BLL. So mention the proper difference and similarities if it has with the relevant code or example
Thanks
To me the M in MVC is about the view model used by the view. Each view has its dedicated view model, that contains all information needed by the view.
These view models are built in the controllers based on the DTO's that you receive from your back-end.
The BLL you are talking about is more the business layer on the back-end, which you don't know in your front-end logic. Often people use a domain driven approach or this layer.
I have been studying various patterns for layering an MVC application and need a little advice. What I currently have is the following:
1) POCO Domain Model, no business logic at all, so basically an anemic Domain Model.
2) EntityFramework with a Repository layer that hands back Domain objects.
3) Service Layer, now I am not sure if this an Application Service Layer or Domain Service Layer, but basically it is an API against the domain model. All of the business logic resides in this layer and assures the domain objects are valid, then hands it off to the repositories to be persisted via EF back to the DB.
4) ASP.NET MVC Application, this application talks to the service layer to get the objects it needs.
I like how this works as it provides a single point of interaction with the domain model, but what I think I need is a layer in between the service layer and the mvc application. The responsibility of this layer would be to transform domain objects to and from view models that the controller could interact with to get the exact data the view needs, and to provide the populated domain objects back to the service layer. Would this be the Application Service Layer and the service layer mentioned above is the Domain Service Layer?
I use AutoMapper to get the domain objects into view models, but I am not sure of the standard of getting them back to a domain object.
Any advice or ideas would be great.
While in theory, your Domain Layer (especially if you are using POCOs) classes are perfectly fine to use in Controllers and Views, in practice, there are always these corner cases and differences.
Typically, objects that controllers and views deal with are simplifications of your Domain Model POCOs or different aggregations of your POCOs from what your Application Service Layer provides/understands.
Therefore, I would not recommend building a separate layer and instead I would recommend adding methods to your View Models to your Domain Layer objects to be sent to your Application Service.
For example, if you have User Domain Level class and UserModel View Model, I would advocate creating User ToUser() instance method on and UserModel UserModel.FromUser(User user) static method to deal with conversion.
You can also mix and match other View Models in there to be able to create Domain Objects.
I am using MVC3 for my application and I have a question about validation. I have a Business Logic layer that is separate from my web layer where I will have a function like CreateUser, which creates a new user for the application to use. I want this function to be accessible in two places: 1) Somewhere in a controller that makes use of it and 2) in a "Setup Data" program that inserts data into the system.
I want to make use of things like ModelState.IsValid to check for all basic validation, but this won't help me for my Setup Data mode (or any other mode that doesn't go through MVC). Is there any way I can still leverage this code, but to contain all validation in my BusinessLogic layer instead of in the controller without having the BusinessLogic layer rely on MVC?
Thanks.
It looks like this article about Service Layers has what I need. Other suggestions are still welcome. Thanks.
Note that the article on service layers still means that you need a dependency on the MVC assembly. After wrestling a bit with this myself recently, I'm now of the opinion that keeping things as separate as possible is a good design. In my model assembly, I have a services folder wherein from, say, a Create() routine, I validate and throw custom exceptions.
The service layer doesn't care who or how these exceptions are consumed. In your MVC app, map them into model state errors collections or whatever. Your design is all the more solid because your model assembly doesn't depend on some validation runner making appropriate use of MVC validation attributes, collections, etc.
I also noticed the article mentions a repository. I know it's all the rage these days but if you're already using an ORM like Entity Framework, a repository is really just a DAO. Reposity is the new Singleton.
In the MVC pattern, the controller is the least reusable, compared to the other two aspects.
Now let's say I have an app (say for Ordering Pizza), which is available both as a web app and a mobile app (say iPhone). So in that case, I think the model (or data) can be reused. The view might not be reusable.
But regarding the controller, is it possible to reuse anything? Let's say if I already have a working web app, can I reuse controller logic for the mobile app as well? Also, what is and where exactly does "business logic" reside in MVC?
The controller calls a service layer. The service layer uses the model to do business logic. Controller never contains business logic. It should only delegate work to the service layer. I consider the service layer as the part that the domain model exposes, you could say it is the "Model" in MVC.
That said, I don't think the MVC frameworks really care if the controller is reusable or not. The important part is the model, which should not change because the service layer code is reused. Besides, if we write our code correctly, the controller will be a very thin layer and reusability should not be a concern.
Can you reuse the controller logic from the web app for a mobile application? I think not, but you could use the service layer. I am sceptical if even the view can be used directly from web to mobile apps, the needs are so different.
I suggest you look at Domain driven design if you are interested in application design and learning how to organize business logic.
Is to possible to have a layout for web-based architecture based on MVC where SOA is the architectural style. Or to rephrase, can services be part of the M,V, C of MVC.If so, what kinds of services can be included in each of them. Also, can you give me a real world example?
In a SOA application you are typically not including the front end (presentation layer). You are consuming those services in your MVC application, or better yet in a separate "model" project that the MVC application uses.
Data Access -> Business Logic -> Services -> Models -> MVC
The point is to use the services to create an abstraction around the base of your application to allow for multiple clients to consume those services.
I tend to term the Model as represented in the client/presentation layer as the ViewModel, it is simply the presentation layers view of the model. Not the actual Domain model.This is needed in a SOA as the context of the consumer of the Model changes often
In SOA`s we try to get to a canonical schema for the contract, as it is quite likely that not all clients now and in the future will require the exact same view of the model.
Thus be it a web client, service client or a desktop client, if you think of the Model in MVC as the ViewModel, this allows you to abstract presentation layer things away from Service layer things, and you get closer to a canonical schema.
So an example View >> Controller >> ViewModel(Model) >> Data Contract >> Service
Examples of how to build a service stack like this can be found here:
SOA Design Pattern
The decision of whether to go with a REST architecture or a full WS-* SOAP is a separate concern and should not affect your choice of MVC as a presentation pattern.
There may of course be other constraints that preclude the use of one or the other.
Choosing a presentation pattern for a new or enterprise web development on the Microsoft platform is a daunting task, in my opinion there are only three; View Model, Model-View-Presenter (MVP) or ASP.NET MVC (a Model2 derivative).
You can read the full article here ASP.NET MVC Patterns
This depends on what you mean by SOA. If you are referring to WS-* standards, I would not recommend MVC, as you will need to write a lot of plumbing to get it to work.
If you are looking for something like a REST service, then the MVC pattern actually works quite well. The request is the HTTP location of the resource, which gets passed to the controller, which loads the data via the model, and then passes it to the view which returns it in whatever form is needed (JSON, XML, Binary, etc). Or, you can often return the result directly, depending on what framework you use.
Erick