Plug into Java with Java Plug-in - Java World

Plug into Java with Java Plug-in

Learn how Sun‘s software tool solves the lag time between Java releases and new browser versions

By Jeff Friesen, JavaWorld.com, 06/01/99

As Java technology matures, Sun Microsystems (Java‘s creator) releases new versions of Java via the Java Development Kit (JDK). Netscape and other browser vendors support each new version by adding that version‘s runtime component -- the Java Runtime Environment (JRE) -- to the next iteration of their browsers. However, the lag time between Sun‘s introduction of a new Java version and the release of browsers that support it has frustrated corporate intranet developers who need to make use of the latest JRE‘s features (and bug fixes). And Microsoft‘s refusal to completely support the JRE in Internet Explorer 4.0 and 5.0 has made the situation even more frustrating for developers.

Sun has a solution to these problems. This solution bypasses the vendor and relies on plug-in technology to distribute newer JREs.

A plug-in architecture -- essentially the combination of an architecture and plug-ins -- is a specification for and implementation of that part of a browser that dynamically loads plug-ins as needed. Both Netscape and Microsoft have added this architecture to their browsers. (The actual implementations of the architecture are quite different: Netscape uses a simple executable implementation, while Microsoft uses its ActiveX object model implementation.)

A plug-in is executable code that is stored in a library file. When referenced via special HTML tags, the browser loads this library, via its plug-in architecture, and starts running the library‘s code. (If you‘ve ever come across a Web page that references Macromedia‘s Shockwave or the VXtreme Web Theater, you‘ve seen examples of plug-ins at work.)

Sun‘s solution is the creation of a plug-in for Java, known as Java Plug-in.

What is Java Plug-in?

Java Plug-in is a software product that serves as a bridge between a browser and an external JRE. A developer "tells" the browser to use this external JRE by placing special HTML tags on a Web page. Once this is done, a browser can run Java applets or JavaBeans components that have access to all the features (within the limits of Java‘s security model) of this external JRE.

Sun released Java Plug-in 1.1 in April ‘98. Shortly thereafter, JavaWorld polled its readership to gauge reaction to this product. The Java Plug-in 1.1.1 and 1.1.2 maintenance releases followed. (See Resources for details on the JavaWorld poll and releases of Java Plug-in.)

Concomitant with the release of JDK 1.2 (now known as the Java 2 platform), Sun has released Java Plug-in 1.2. However, unlike previous releases, this release is currently only available for the Microsoft Windows (95/98/NT) platform. Sun is currently working to make Java Plug-in 1.2 available for its Solaris platform.

This article explores Java Plug-in 1.2, starting with a discussion on how to download and install this technology. It is based on my experience using Java Plug-in 1.2 with the Internet Explorer 3.02 and Netscape Communicator 4.5 browsers, under the Windows 95 operating system.

Get plugged in!

Java Plug-in 1.2 is currently packaged with JRE 1.2. If you want to preinstall Java Plug-in, download and install JRE 1.2 from Sun‘s Web site, which is linked to in the Resources section. Or, you can choose to have your browser download Java Plug-in (with minimal intervention from you, depending on your browser) when you "surf" to a Web page that references that plug-in. Here‘s how:   Continued

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