Overview

Java Web Start Technology

Java Web Start is a helper application that gets associated with a Web browser. When a user clicks on a link that points to a special launch file (JNLP file), it causes the browser to launch Java Web Start, which then automatically downloads, caches, and runs the given Java Technology-based application. The entire process is typically completed without requiring any user interaction, except for the initial single click.

JNLP URLs are also directly openable from the JAWS Application Manager and can be bookmarked. Moreover, they may be .html or .jnlp files.

From a technology standpoint, Java Web Start has a number of key benefits that make it an attractive platform to use for deploying applications:

• Java Web Start is built exclusively to launch applications written to the Java 2 SE platform. Thus, a single application can be made available on a Web server and then deployed on a wide variety of platforms, including Windows 98/NT/2000/ME/XP, Linux, and the Solaris^TM Operating Environment. The Java platform has proven to be a very robust, productive, and expressive development platform, leading to a significant cost savings due to minimized development and testing costs.
• Java Web Start supports multiple revisions of the Java 2 platform, Standard Edition. Thus, an application can request a particular version of the platform it requires, such as J2SE^TM 1.4.0. Several applications can run at the same time on different platform revisions without causing conflicts, and Java Web Start can automatically download and install a revision of the platform if an application requests a version that is not installed on the client system.
• Java Web Start allows applications to be launched independently of a Web browser. This can be used for off-line operation of an application, where launching through the browser is often inconvenient or impossible. The application can also be launched through desktop shortcuts, making launching the Web-deployed application similar to launching a native application.
• Java Web Start takes advantage of the inherent security of the Java Platform. Applications are by default run in a protective environment (sandbox) with restricted access to local disk and network resources. It allows the user to safely run applications from sources that are not trusted.
• Applications launched with Java Web Start are cached locally. Thus, an already-downloaded application is launched on par with a traditionally installed application.

The technology underlying Java Web Start is the Java ^TM Network Launching Protocol & API (JNLP). This technology is currently under development via the Java Community Process (JCP). Java Web Start is the reference implementation (RI) for the JNLP specification. The JNLP technology defines, among other things, a standard file format that describes how to launch an application called a JNLP file.

Where to find Java Web Start

See the Java Web Start web site, http://java.sun.com/products/javawebstart/, for availability of Java Web Start downloads. The JNLP specification can be found at http://java.sun.com/aboutJava/communityprocess/final-draft/jsr056.

Requirements

Desktop/Client requirements:

The client machine requires support for the Java Runtime Environment (JRE), version 1.2.2 or later. Java Web Start is available for Windows 98/NT/2000/ME/XP, the Solaris Operating Environment, and Linux.

See the README document for details.

Server requirements:

Applications can be deployed from any standard Web server. In order to use Java Web Start, the Web server must be configured with support for a new MIME type as explained below.