How can I implement the MVC design pattern using JSP?
The MVC (Model View Controller) design pattern is a pattern/architecture that can be used by GUI's. It seperates the application's data, user interface and control logic into three separate entities. This ensures the system will be more maintainable in the future as changes to one component will not have an affect on the others.
The MVC pattern also conforms with the JSP Model 2 architecture.
The MVC pattern can be easily implemented in web applications using JSTL core, JSP, Servlets and JavaBeans.
JSTL makes it easy for HTML designers to use dynamic data in their pages without having to learn in depth java. The tags are in a recognizable HTML like format meaning a smaller learning curve than taking on the JSP specification after taking on the Java specification.
JSTL also makes it easy for web developers who are developing all aspects of the application in helping you keep the content separate from the display by keeping your JSP clean from any Java code. Since JSTL and its EL (expression Language) are really only suited for accessing data, it forces you to use a MVC pattern so long as you keep all JSP and Java syntax/code out of the JSP pages.
A common scenario might look like this, a user sends a request to a server. The request is handled by a Servlet (the controller) which will initialize any JavaBeans (the model) required to fulfill the user's request. The Servlet (the controller) will then forward the request, which contains the JavaBeans (the model), to a JSP (the view) page which contains only HTML and JSTL syntax. The JSTL will format the data into a human readable format before being sent back to the user. Thus completing the full MVC process.
JSTL also has a tag library for XML processing, this could be used in an MVC environment as you could replace the JavaBeans with an XML document to describe your data, so long as the XML is still constructed in a controller such as a Servlet before being passed to the JSP (the view).
JSTL also has a tag library for database access, using this in your JSP (the view) pages would NOT comply to the MVC pattern as there will be no separation between the model and the view.