As we know Struts Frameworks follows model -view-controller (MVC) architecture to build applications. As MVC is most concepts of Struts Frameworks so we must have clear understanding about each later. Here we are going to cover Model and its components. 

 What Is the Model? 

In an MVC application Model layer is most important and largest part of code .Model is used for access data from database which will be calculated, manipulated by Model. The Model also responsible for update, insert and select data from database. We can say Model is the core of the application. Model layer should be self-contained and functionally not depends from the View and Controller layers. Model can be used by any view.

 Model Layers 

We can break Model Layer into three parts. 
External interface: It provides an interface that will use by external code. 
Business logic: It provides the business functionality for an application. 
Data access Here the code communicate with database.


Struts 2.0 Tutorial and Example
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Spring 2.5 MVC Tutorial
Spring 2.5 MVC Example