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 have no other design change choices then what you may need is a JVM shutdown hook, which can be added to run a piece of code when System.exit is called.

Shutdown Hooks are a special construct that allow developers to plug in a piece of code to be executed when the JVM is shutting down. This comes in handy in cases where we need to do special clean up operations in case the VM is shutting down.

You can add a shutdown hook as mentioned here:

Runtime.getRuntime().addShutdownHook(Thread)

Read more about shutdown hooks here:

http://java.dzone.com/articles/know-jvm-series-2-shutdown

Word of Caution:

We must keep in mind is that it is not guaranteed that shutdown hooks will always run. If the JVM crashes due to some internal error, then it might crash down without having a chance to execute a single instruction. Also, if the O/S gives a SIGKILL (http://en.wikipedia.org/wiki/SIGKILL) signal (kill -9 in Unix/Linux) or TerminateProcess (Windows), then the application is required to terminate immediately without doing even waiting for any cleanup activities. In addition to the above, it is also possible to terminate the JVM without allowing the shutdown hooks to run by calling Runime.halt() method.