Chapter 22. Using Java with JavaScript

As we discussed in Chapter 14, Netscape 3 and later and Internet Explorer 4 and later both allow JavaScript programs to read and write the public fields and invoke the public methods of Java applets embedded in HTML documents. Netscape supports JavaScript interaction with Java applets through a technology known as LiveConnect. Internet Explorer instead treats every Java object (including applets) as an ActiveX control and uses its ActiveX scripting technology to allow JavaScript programs to interact with Java. Because Netscape's technology is specifically designed for communication between JavaScript and Java, it has some features that IE's ActiveX technology cannot provide. In practice, however, the two technologies are fairly compatible. Although this chapter is based on Netscape's LiveConnect, the key features it describes work in IE as well.^[1]

^[1] Note that Netscape 6 was released with poor support for LiveConnect but that it is fully implemented in Netscape 6.1 and later.

This chapter begins with a discussion of how you can use JavaScript to script Java applets, how your Java applets can invoke JavaScript code, and how (in Netscape only) you can use JavaScript to work directly with Java system classes. It then documents the nitty-gritty details of how LiveConnect works. It assumes you have at least a basic familiarity with Java programming (see Java in a Nutshell, by David Flanagan, and Learning Java, by Patrick Niemeyer and Jonathan Knudsen, both published by O'Reilly).