Cache and System Format
In Java SE 6, the cache format has been fully changed. That's why, any existing code using previous format of cache for Java Web Start or Java Plug-in will no longer work. Existing applications cache will be upgraded and converted to the new format of cache when the first time you launch a Java Web Start application, or by launching the cache viewer using javaws-viewer. And System cache will upgraded when the first time you run Java Web Start application in system mode, or just launching javaws - system.
Download Engine and Cache Consolidation
Download Engine and entire caching mechanism are redesigned and consolidated between Java Web Start and Java Plug-in. This include some new features in Java Web Start:
In Java SE 6, signed Java Web Start applications are not affected but the unsigned Java Web Start applications specify a version trigger a security warning, requiring explicit user permission before running the application.
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