With newer versions of Java and older firmware on HP equipment you may run into Java errors trying to administer the devices through the web interface. Adding the IP or FDQN to the Java exceptions alone will not work now that High security is the lowest level allowed in the Java control panel. Below are a few fixes I have found.
For an HP ProCurve 2810 switch there needs to be an additional entry in the java control panel in the form of http://x.x.x.x/classes/agent.jar
For an HP 4650 printer I found the java.policy file needs a line to allow the specific port used by the printer interface, this case 161, that is not a normal HTTP/HTTPS port. The file was located in “C:\Program Files (x86)\Java\jre1.8.0_77\lib\security” which could be different based on your JAVA version. A line similar to ‘permission java.net.SocketPermission “x.x.x.x:port#”, “connect, accept”;’ will need to be put in the grant section of the file. This is in addition to the http://x.x.x.x in the Java control panel
I hope this helps some other people that run into the same issues. If you have any other fixes I would love to hear them.