[play 1.2.7]How should I protect my play app? Can I use a Dongle?

[zxsoft]

Because the application is used for production in a car line, it must be deployed in a intranet, not internet. So I have to deploy the application on the customer's computers. I know how to precompile and deploy without java files,but what if they decompile the classes? 

Can I use a Dongle to protect my application? Or is there any other way to protect my application(As it will be deployed on customer's computers)? Thanks a lot!