3-Tier architectuire

In my opinion, you have to distinguish between the MVC pattern and the 3-tier architecture. To sum up:

3-tier architecture:

• data: persisted data;
• service: logical part of the application;
• presentation: hmi, webservice...

The MVC pattern takes place in the presentation tier of the above architecture (for a webapp):

• data: ...;
• service: ...;
• presentation:
  • controller: intercepts the HTTP request and returns the HTTP response;
  • model: stores data to be displayed/treated;
  • view: organises output/display.

Life cycle of a typical HTTP request:

1. The user sends the HTTP request;
2. The controller intercepts it;
3. The controller calls the appropriate service;
4. The service calls the appropriate dao, which returns some persisted data (for example);
5. The service treats the data, and returns data to the controller;
6. The controller stores the data in the appropriate model and calls the appropriate view;
7. The view get instantiated with the model's data, and get returned as the HTTP response.