服务器和客户端框架

Question

I know this a fairly common question but after reading a lot I still can't understand this concept.

What I understand so far is that the main difference about a server side and a client side language is that the first one needs to be interpreted by the server to be sent to browser and the second one doesn´t.

I've worked with Vaadin and I know that is a server side framework because the java code needs to be interpreted to HTML and Javascript to be sent to browser. But then I've read that GWT is a client side and I can't understand why because we design all the page elements with Java widgets and they need to be interpreted to HTML and Javacript right? So, shouldn't GWT be a server side framework?

And what about JSF? I'm working with Primefaces and I develop xhtml files that uses beans to get server information. That means that the xhml files are client side and the Java beans are server side right?

Thanks!

Answer 1

It's not about the language the code is written, it's about where it runs.

GWT is a client-side technology just like TypeScript or CoffeeScript: they first have to be compiled or transpiled (a true compilation in the case of GWT) to JavaScript. The compilation has to be done at build time, before you deploy the app to your server. Once compiled to JavaScript, you don't need a server: the scripts can be packaged into browser extensions, mobile apps, or just run out of the filesystem (or be deployed to a Node.js server to run as server-side code !).
You can draw a parallel with Dart: dart2js converts Dart code to JavaScript so it can run in the browser, and/or you can run Dart code in a DartVM on the server side.

JSF is a server-side technology: things run in the server and generate code (HTML, JavaScript, CSS) to be interpreted by the browser (client).

I can't really tell for Vaadin as I don't know its architecture. If GWT Widgets have to be compiled upfront, then it'd be a server-side technology, generating highly dynamic web pages (so they could even run offline). If it compiles GWT widgets on-the-fly, then it'd be a bit in between; but it's primarily a server-side technology.

Answer 2

Vaadin use GWT to keep client-side code base in Java. GWT compiles Java code into browser dependent JavaScript. Without GWT all code should be written in JS. Vaadin is RIA application framework, so managing complex widgets code (look into Table source code) with pure JavaScript would be painful and not easy. You can write some logic in client side and also you can use pure JavaScript in Vaadin7. It's easy to extend and gives solid foundations to write good and rich UI with minimal use of the JavaScript.