WebSocket is a TCP-based protocol like HTTP which is part of HTML 5 specification. Unlike HTTP which is a request response synchronous protocol, WebSocket provides a two way (full-duplex) communications channel over a single TCP connection and messages (textual and binary) can be sent between client and server asynchronously without the overhead of HTTP request/response life cycle.

We will write a simple JavaFX application that displays a “Hello World” button. We will handle any button click events to print “Hello World” in the console. The program can be run from command line or from an IDE like eclipse, but without the Eclipse Plugin for JavaFX and Scene builder.

JavaFX is a software platform for creating and delivering rich internet applications (RIAs). Swing and Adobe Flex are similar technologies. Though JavaFX is primarily suitable for desktop applications, it is also suitable for enterprise applications. We will first see where JavaFX fits and its future by comparing it with similar technologies, and then we will see its version and history in brief, an overview of some JavaFX tools and later we will see some sample JavaFX programs.

We will see how to write to a file in file system from a servlet. To write to a file in the root folder of a web app, we will need the real path to it. Using the path we can write to the file. Note that the WeContent folder you see in eclipse during development becomes the root folder of the web app, as we archive the contents of the WebContent folder to create a war file.

Parameters may come into our application from the client request, or may be configured through deployment descriptor (web.xml) elements or their corresponding annotations. When you submit a form, form values are sent as request parameters to a web application. In case of a GET request, these parameters are exposed in the URL as name value pairs and in case of POST, parameters are sent within the body of the request.