Exiting an application gracefully?

Question

I have an application with a well defined Try/Catch/Finally chain that exits and executes the finally block just fine under normal conditions, however when someone premature

Answer 1

If you happen to have such threads which can legally be stopped at any time, at any point at all within their loop, at any point within any method which they invoke, and may I warn you that it is very unlikely that you do, then you can stop all of them upon program exit. This will result in an exception being thrown in each thread, and the finally blocks will execute.

However, the proper way to achieve your goal and have GUI decoupled from the program logic, is to issue a single "exit" signal from the GUI, which will trigger all the application cleanup, which is written in an entirely different class. If you have running threads, then implement the interrupt mechanism in each of them.

There are many ways to achieve the exit signaling. For example, your business code could register a GUI listener for a special event, which would trigger the cleanup. You could also have a thread which doesn't do anything else but await on a CountDownLatch which would be countDown from the GUI.

Please, do not at any cost use a shutdown hook. This is the dirtiest mechanism imaginable, and it is there only as a last resort, when all regular cleanup procedures fail. It is never to be used as a part of the regular shutdown routine.

In summary, there is no royal way to clean application shutdown. You must implement specific mechanisms for each specific concern.