WebSphere Application Server - IBM Redbooks

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Figure 2-8 Model layer
Model
Please note that the model does not have any dependences on views or
controllers.
View
The view layer implements a rendering of the model. The responsibility of the
view is to know what parts of the model’s state are relevant for the user, and to
query the model for that information. The view retrieves the data from the model
or receives it from the controller, and displays it to the user in a way the user
expects.
Controller
The controller’s responsibility is to capture user events and to determine which
actions each of these events implies, depending on both the user’s and the
application’s state. This usually involves verifying pre- and post-conditions.
These actions can then be translated to messages to the model and view layers,
as appropriate.
Dependencies between MVC layers
Figure 2-9 on page 32 shows the dependencies allowed in the MVC pattern.
Note that the fewer dependencies your layers have, the easier it will be for the
layers to respond to requirement changes.
Chapter 2. Application design 31