Enhancements to
Java Web Start in J2SE 5.0

Elimination of Application Manager: The J2SE 5.0 release no longer contains the Application Manager. Its major functionality is now contained in the Java Control Panel (see item 3 below) and the JNLP Cache Viewer (see item 4 below). The remaining functionality— viewing web pages containing JNLP links—is better served by a web browser.

Elimination of Developer Bundle: Java Web Start is now fully integrated into the JRE and the JDK. The items which were previously contained in a separate developer bundle are now contained in the JDK. The documentation which was previously contained in the developers bundle is now available online. The JDK now contains a samples directory with sample source code to four Java Web Start applications, a sample JRE installer, and the JNLP download servlet. The JDK now also contains jardiff.jar, jnlp.jar, and jnlp-servlet.jar.

JNLP Cache Viewer: The JNLP Cache Viewer replaces the functionality of the Application Manager's "downloaded Applications" view. Now all applications, applets, libraries and installers are shown. Available applications can be launched online or offline, removed, or restored from the web. All JNLP files are now kept in the cache (even those without href parameters).

System Cache: Java Web Start now contains both system and user caches. The system administrator can now pre-load applications and shared libraries into the system cache so that multiple users can share the same resources.

Import Facility: Java Web Start now contains an import facility. This can be used for CD installs, where code is initially loaded from one location and then updated from another. It can also be used to pre-install applications and libraries in either the user or system cache without running the applications.

Desktop Integration: (1) Desktop integration of applications has been extended to GNOME and enhanced to allow an application's JNLP file to specify what integration to do. The JNLP file can now suggest desktop and/or menu and specify submenu names. (2) On Windows and on Unix running GNOME 2.0 or above, Java Web Start applications can now register themselves to be the primary handler for specific MIME types and extensions on the desktop or file system (but not as links in web pages). (3) Now other related content—HTML links, native content, and related JNLP applications—can be included in the desktop integration of an application.

API Enhancements: The JNLP API has been extended to contain an Extended Service and a Single Instance Service. The Extended Service contains file IO APIs not available in the original spec. The Single Instance Service provides a mechanism whereby applications can insure that multiple invocations of the same application will cause new arguments to be passed to the original instance. This avoids the overhead of relaunching Java. Note that the Single Instance behavior will only be enabled after the application calls the Single Instance API in the JNLP application.

VM arguments: A JNLP file can now request arbitrary arguments to the virtual machine. Previous JNLP applications could only use the initial-heap-size and max-heap-size arguments to the j2se element; now a java-vm-args argument has been added. Java Web Start will honor the requests for any normal java and -X arguments that it considers "safe". A list of all such arguments will be included with each release so that the JNLP Spec does not need to change.

A JNLP applications running in a sandbox can now print with full support using the Java Printing APIs: Whenever the JNLP application tries to print, Java Web Start will pop up a security dialog asking the user for permission for the application to print. This provides JNLP applications with complete printing support; previously they could only use JNLP printing APIs. This is similar to the applet printing behaviour in Java Plug-in.