Re: Java servlet on browsers: dying or kicking ?
On 12/29/2012 7:22 AM, Arved Sandstrom wrote:
On 12/28/2012 06:51 PM, Arne Vajh?j wrote:
On 12/28/2012 12:50 PM, lipska the kat wrote:
What I inevitably end up with is a slightly less that perfect decoupling
but I like to think that eventually, given the appearance of a truly
scalable way to persist entire Object trees I will be able to produce a
business system that will be completely decoupled from earthly
considerations like UI and database
I thought a business logic layer by definition was separate
from UI layer and data access layer.
I do such a heavy combination of SOA and web app work that I like layers
that work for both. For my purposes Martin Fowler's Service/Application
layer picture (http://martinfowler.com/eaaCatalog/serviceLayer.html)
serves nicely as a starting point.
In that picture business logic is mostly in the Domain/Model layer,
including business rules, and the Service/Application layer consists of
operations that cannot be assigned to any one given domain object.
I see a good, solid Service/Application layer as being one that actually
provides services in the SOA sense. Not web services, but _services_.
These then become available for orchestration in different ways.
The 3 layer model with PL, BLL and DAL are very widely used, but
other models are certainly possible.
A DL and AL makes perfectly sense to me.
But DL and AL will still be separate from PL and DAL just like BLL.
In a web app scenario, and I stress that this is *my* approach, the MVC
Model is generally the Fowlerian Service layer (plus everything inside
it) + extra stuff that is perhaps best characterized as a view-model.
That is how I see M as well.
I emphatically don't delineate layers by technology used, or even by
location. A clean, understandable architectural picture can deal with,
and explain, business logic in Javascript on a mobile browser, and also
business logic in a DB stored procedure.
Business logic can be put in all tiers.
But it may not be equally good design.
Arne