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Re: MVC Partner

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On 26/11/14 19:16, Leonan Luppi wrote:
> Hello Guys,
>
> I have some doubt about MVC. Someone could solve please?
>
> So for my "M" it's need to be my mirror of DB (Entity mapped my JPA for example)?
>
> For my "V" it's need to be interfaces which only show and send to my controller?
>
> For my "C" it's need to be all business rules, calling my DAO to result from DB ?
>
> Someone can give an example please?
>

I really think that there is an awful lot of mis-information out there 
about MVC. For example the wikipedia article mentioned by another 
responder talks about MVC being a 'design pattern' when effect it is a 
combination of several design patterns. I think 'paradigm' might be a 
better word.

The *original* idea behind MVC was that you had a Model, this could be 
any persistent store, often but not exclusively a database. The 
Controller was responsible for updating the Model in response to 
interactions with the View. There could be many Views on the Model each 
of which registered themselves with the Controller and each of which 
were updated in response to an interaction with any one of them. so for 
example you could have 3 Views, possibly on 3 different devices and if 
any View was modified by a 'user' the state of the Model was first 
updated by the Controller which then updated *all* the views that were 
registered with it at the time. The finer details escape me, it was some 
years ago when I studied this.

With the advent of Java, Sun came up with something called Model2 IIRC.
In this case you still had your persistent store but the Controller was 
a Servlet (or rather the interface to the Controller was a Servlet) and 
the view was (classically) implemented as a JSP.

The fundamental difference is that because http is a request/response 
protocol and there is no way to 'push' changes initiated by one view to 
other views.

Things may be slightly different now with the advent of asynchronous 
technologies such as Web Sockets.

So, in the classic 3 tier Model 2 web application you have an SQL 
database which would be your Model, a Servlet engine such as Tomcat 
which would host your Servlets (your Controllers) and a (arbitrary) 
client, let's say in this case a web browser, to which you would deliver 
your View implemented as a JSP

Your business logic is typically accessed through a facade accessed by a 
Servlet, your business logic would communicate with a facade onto your 
database, this would initially be an Interface.

The single most important thing to remember is that your business logic 
should be completely decoupled from the View *and* from the Model. In 
this way you can deliver your content to any interface, not just a web 
interface and persist you data to any type of persistence mechanism.


-- 
lipska the kat - treacherous feline.
Proudly nominated for IPOTY 2014 - LIGAF
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MVC Partner Leonan Luppi <leonan.luppi@gmail.com> - 2014-11-26 11:16 -0800
  Re: MVC Partner Arne Vajhøj <arne@vajhoej.dk> - 2014-11-26 14:56 -0500
    Re: MVC Partner Leonan Luppi <leonan.luppi@gmail.com> - 2014-11-26 14:54 -0800
      Re: MVC Partner Arne Vajhøj <arne@vajhoej.dk> - 2014-11-26 18:07 -0500
      Re: MVC Partner Martin Gregorie <martin@address-in-sig.invalid> - 2014-11-26 23:22 +0000
  Re: MVC Partner lipska the kat <lipskathekat@example.com> - 2014-11-26 20:40 +0000
    Re: MVC Partner Leonan Luppi <leonan.luppi@gmail.com> - 2014-11-26 15:01 -0800
      Re: MVC Partner lipska the kat <lipskathekat@example.com> - 2014-11-27 08:56 +0000

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