How can I launch older versions of my Java WebStart application, that are built and run with Java 7u21 or earlier, even if Java 7u25 is installed locally on the client? Application launch and behaviour must be reliable and consistent.
Background:
As of 7u25 (and later), Java Webstart applications launch with a different class loader than pre-7u25.
My Java Webstart application has supported versions that were built with older versions of the JDK (e.g. Java 5, 6, 7u21 or earlier). These applications run with their required JRE version, enforced through JNLP. Once Java 7u25 is installed locally, these older applications fail to launch, due to classloader differences.
The question is: what is required to run older Java WebStart applications even if 7u25 (or later) Java Webstart is installed locally on the client?