Like a few others, I got bitten by a Mountain Lion upgrade recently.
When installing this update from Apple About Java for OS X 2012-006 — HT5495 that was released on 16 Oct 2012, the information provided did clearly state the following:
“This release updates the Apple-provided system Java SE 6 to version 1.6.0_37 and is for OS X versions 10.7 or later. This update uninstalls the Apple-provided Java applet plug-in from all web browsers. To use applets on a web page, click on the region labeled “Missing plug-in” to go download the latest version of the Java applet plug-in from Oracle. This update also removes the Java Preferences application, which is no longer required to configure applet settings.”
But what it didn’t say was that when you try and upgrade the plug-in, as advised, in Google Chrome you cannot, as it isn’t a 64-bit application in Mountain Lion:
“Chrome does not support Java 7. Java 7 runs only on 64-bit browsers and Chrome is a 32-bit browser. If you download Java 7, you will not be able to run Java content in Chrome and will need to use a 64-bit browser (such as Safari or Firefox) to run Java content within a browser. Additionally, installing Java 7 will disable the ability to use Apple Java 6 on your system.”
So, you have to use Safari or Firefox to handle web pages using applets.
For a very good discussion of the security issues with Java and Apple’s rationale for their approach see: Using Java in Mac OS X, Thomas’ Tech Corner
To test if the Java Applet is working in your browser try this link: Test Java Applet — Verify Java Version