MVC in Java
MVC stands for Model View and Controller. It is a design pattern that separates the business logic, presentation logic and data.
Controller acts as an interface between View and Model. Controller intercepts all the incoming requests.
Model represents the state of the application i.e. data. It can also have business logic.
View represents the presentaion i.e. UI(User Interface).
Advantage of MVC (Model 2) Architecture
- Navigation Control is centralized
- Easy to maintain the large application
If you new to MVC, please visit Model1 vs Model2 first.
Model 1 and Model 2 (MVC) Architecture
Before developing the web applications, we need to have idea about design models. There are two types of programming models (design models)
- Model 1 Architecture
- Model 2 (MVC) Architecture
Model 1 Architecture
Servlet and JSP are the main technologies to develop the web applications.
Servlet was considered superior to CGI. Servlet technology doesn’t create process, rather it creates thread to handle request. The advantage of creating thread over process is that it doesn’t allocate separate memory area. Thus many subsequent requests can be easily handled by servlet.
Problem in Servlet technology Servlet needs to recompile if any designing code is modified. It doesn’t provide separation of concern. Presentation and Business logic are mixed up.
JSP overcomes almost all the problems of Servlet. It provides better separation of concern, now presentation and business logic can be easily separated. You don’t need to redeploy the application if JSP page is modified. JSP provides support to develop web application using JavaBean, custom tags and JSTL so that we can put the business logic separate from our JSP that will be easier to test and debug.
As you can see in the above figure, there is picture which show the flow of the model1 architecture.
- Browser sends request for the JSP page
- JSP accesses Java Bean and invokes business logic
- Java Bean connects to the database and get/save data
- Response is sent to the browser which is generated by JSP
Advantage of Model 1 Architecture
- Easy and Quick to develop web application
Disadvantage of Model 1 Architecture
- Navigation control is decentralized since every page contains the logic to determine the next page. If JSP page name is changed that is referred by other pages, we need to change it in all the pages that leads to the maintenance problem.
- Time consuming You need to spend more time to develop custom tags in JSP. So that we don’t need to use scriptlet tag.
- Hard to extend It is better for small applications but not for large applications.
Model 2 (MVC) Architecture
Model 2 is based on the MVC (Model View Controller) design pattern. The MVC design pattern consists of three modules model, view and controller.
Model The model represents the state (data) and business logic of the application.
View The view module is responsible to display data i.e. it represents the presentation.
Controller The controller module acts as an interface between view and model. It intercepts all the requests i.e. receives input and commands to Model / View to change accordingly.