JNLPClassLoader returns illegal URL values from ClassLoader.findResource()
if the base directory for the cache contains characters illegal in URL's.
For example, on Windows the default deployment.userHome is commonly:
C:/XXX/Application Data/Sun/Java/Deployment
this will result of cached resource being returned as:

jar:file:C:/XXX/Application Data/Sun/Data/Deployment/cache/http/YYY/resource.jar

the space in "Application Data" is not a legal character in a url and should
be encoded as "%20". the returned url should be:

jar:file:C:/XXX/Application%20Data/Sun/Data/Deployment/cache/http/YYY/resource.jar