JavaScript: The Definitive Guide, 5th Edition

Chapter 23. Scripting Java Applets and Flash Movies

A plug-in is a software module that can be “plugged in” to a web browser to extend its functionality in some way. Two of the most widely deployed (and, not coincidentally, the most powerful) plug-ins are the Java plug-in from Sun Microsystems and the Flash Player from Adobe (which acquired Macromedia). The Java plug-in enables a browser to run applications known as applets written in the Java programming language. The Java security system prevents untrusted applets from reading or writing files on the local system or doing anything else that could alter data or compromise privacy. Despite the security restrictions that are imposed on applets, the Java plug-in ships with a huge library of predefined classes that applets can take advantage of. This library includes graphics and GUI packages, powerful networking capabilities, XML parsing and manipulation packages, and cryptographic algorithms. Java 6, in prerelease at the time of this writing, will include a complete suite of packages for web services.

The Flash Player is extraordinarily popular and almost universally deployed. It is a virtual machine that interprets “movies,” which may include true streaming video but typically consist of animations and rich GUIs. Flash movies may include scripts written in a language known as ActionScript. ActionScript is a variant of JavaScript, with the addition of object-oriented programming constructs such as classes, static methods, ...