Sun's Activator

One of the troubles that arises from dealing with the rapidly evolving Java specification is the existence of extinct species (read: versions) that will not die. Simply put, it would be great if everything were compatible with the latest version of the Java Development Kit (JDK), but everything isn't. Such is the raison d'etre of Sun's Activator.

Activator allows you to run JDK 1.1-compliant applets in browsers that are not JDK 1.1-compliant (i.e., browsers whose Java virtual machines [JVMs] are not JDK 1.1-compatible). At the time o f this writing, Activator was available for Internet Explorer 3.02 or later. Activator for Netscape's Navigator 3.0 or later was expected by mid-January.

Activator relies on Microsoft's ActiveX/Component Object Model (COM) technology and Netscape's plug-in architecture to extend the capability of the browser to include JDK 1.1 support. Unfortunately for some of us, this arrangement requires a device-specific implementation for the hardware platform and, consequently, Macintosh users are left out in the cold for now.

Another consequence of Activator's modus operandi is that it does not replace the browser's existing JVM. Instead, you must specify explicitly in HTML that a particular applet is to run in the Java run-time environment (JRE).

Ordinarily, you use the <applet> tag to embed a Java applet in an HTML document. An Activator-run applet, however is encased in what amounts to a JavaScript wrapper. In IE, this wrapper calls the Activator ActiveX cont rol, passing to it as an argument the path to the Java applet .class file. Upon execution of the HTML page, the Activator control wakes up, loads the applet into the JRE, and -- voilà! -- the client sees a JDK 1.1-compliant applet.

What this means, of course, is that if you have piles of HTML files that you want to make Activator-ready, you're going to have to spelunk through them and modify all the applet tags. To make that task less arduous and error-prone, Sun has made available the HTML converter. Turn the converter loose on an HTML file and it will replace any instance of an <applet> tag it finds with the JavaScript wrapper. It also places any applet parameters in their proper locations in the wrapper. (For the untrusting, the HTML converter keeps a backup copy of all converted files.)

There's one final consideration: On the client side, a user of an Activator-based Web page must first download the Activator control (or plug-in). Agreed, this is a one-time penalty, but it's a 2. 8-MB-download-time penalty, during which time a user sees only a status message: "Installing components." (In addition, for IE at least, the client must have the security setting such that downloaded controls are allowed to run.) Time will tell if the citizens of the Internet world are willing to take that hit to be JDK 1.1.x-compliant.