Re: The "Presentation" Layer

john e wrote:

Joe wrote:

he entire page-at-a-time browser interface all the way up to JSP Model 2 has been server/client

I don't understand. Whether page-at-a-time or ajax, it's always client/server and not server/client because the browser always initiates the request. The browser is under control. The server responds to requests, whether this is with a complete page or simply some data.

That's typically JSP Model 1. In JSP Model 2, the servlet on the host puts data into the session, and then initiates the display of a specific JSP page. That page is displayed to the user, who then hits a button to submit the page back to the same servlet.

In JSP Model 1, each button on the screen initiates a request to a different page. Frameworks like Struts attempted to externalize that application flow to some degree, but it still wasn't quite the same. With JSP Model 2, the control is moved entirely to the servlet. The user simple enters data and hits a button; the application determines the next page to display.

Having all application code on the server and "nothing" (i.e. only HTML) on the client doesn't make it server/client. It's just that you're entire application is structured as functions that are executed as a result of the browser (client) making requests.

Again, it's how you write the servlet. The primary characteristics of JSP Model 2 are: the servlet identifies the page to display, and the SUBMIT button on the JSP page returns to the calling servlet. These two design components turn it from a rough client/server to server/client.

If the server outputs a complete page to the browser then this is a response to a request of the client. When done the server simply waits for the next request. This is different from server/client where the client program on the host is under control. It outputs a screen to the terminal whenever it wants to, not after receiving a request from the terminal.

Again, in JSP Model 2, the servlet is the controller. It determines the next page to display.

Joe