Web Services/Application History.

Java Servlets in early days:

• Advantages:
• Much better than CGI, ISAPI, lighter plumbing.
• Allowed for scalable, robust web development.
• Disadvantages
• Hard to incorporate sophisticated HTML.
• Harder to update HTML design, which could be designed in Dream Weaver.
• Too much dependency on HTML embedded in Java code.

Then comes JSP:

• Advantages: 
• Closer to HTML.
• Same as servlets with improvement in manipulation of display characteristics.
• Disadvantages:
• developers must deal more directly with the view of the application.
• Syntax quickly becomes cryptic because of the mixing of code and display
• Too much dependency on JAVA embedded in HTML.

Meet Model-View-Controller:

• SmallTalk Language creator in 1980's came up with MVC. 
• Gang of Four wrote "Design Patterns" in 1994 (Wiki).
• Model represents the data that application is about. (eg. a list of numbers)
• View is the visual representation of the model (eg. a spreadsheet/graph/chart)
• Controller is how they interact (eg. keyboard changes cell value, mouse changes graph size)

MVC applications in Java web development (Model 2):

• The model is represented by Java Beans (or Enterprise Java Beans)
• Java Beans - a method to encapsulate information.
• The view uses JSP.
• The controller is a servlet that drives the process.
• How it works:
• The user requests a servlet via a URL or a link.
• The servlet instantiates one or more Java Beans and calls methods on them.
• The beans with displayable fields are added to one of the standards collections (eg.request or sessions)
• Control is forwarded to a JSP to display the results.

Stay tuned...