Why not rather add a ShutdownHook to your application?
A shutdown hook is simply an initialized but unstarted thread. When
the virtual machine begins its shutdown sequence it will start all
registered shutdown hooks in some unspecified order and let them run
concurrently. When all the hooks have finished it will then run all
uninvoked finalizers if finalization-on-exit has been enabled.
Finally, the virtual machine will halt. Note that daemon threads will
continue to run during the shutdown sequence, as will non-daemon
threads if shutdown was initiated by invoking the exit method.
This will allow your jar to terminate gracefully before being shutdown:
public class ShutdownHookDemo {
public void start() {
System.out.println("Demo");
ShutdownHook shutdownHook = new ShutdownHook();
Runtime.getRuntime().addShutdownHook(shutdownHook);
}
public static void main(String[] args) {
ShutdownHookDemo demo = new ShutdownHookDemo();
demo.start();
try {
System.in.read();
}
catch(Exception e) {
}
}
}
class ShutdownHook extends Thread {
public void run() {
System.out.println("Shutting down");
//terminate all other stuff for the application before it exits
}
}
It is important to note
The shutdown hook runs when:
- A program exists normally. For example, System.exit() is called, or the last non-daemon thread exits.
- the Virtual Machine is terminated. e.g. CTRL-C. This corresponds to kill -SIGTERM pid or
- kill -15 pid on Unix systems.
The shutdown hook will not run when:
- The Virtual Machine aborts
- A SIGKILL signal is sent to the Virtual Machine process on Unix systems. e.g. kill -SIGKILL pid or kill -9 pid
- A TerminateProcess call is sent to the process on Windows systems.
Alternatively if you must you can use this to call a method in a class:
public class ReflectionDemo {
public void print(String str, int value) {
System.out.println(str);
System.out.println(value);
}
public static int getNumber() { return 42; }
public static void main(String[] args) throws Exception {
Class<?> clazz = ReflectionDemo.class;//class name goes here
// static call
Method getNumber = clazz.getMethod("getNumber");
int i = (Integer) getNumber.invoke(null /* static */);
// instance call
Constructor<?> ctor = clazz.getConstructor();
Object instance = ctor.newInstance();
Method print = clazz.getMethod("print", String.class, Integer.TYPE);
print.invoke(instance, "Hello, World!", i);
}
}
and to load a class dynamically:
ClassLoader loader = URLClassLoader.newInstance(
new URL[] { yourURL },
getClass().getClassLoader()
);
Class<?> clazz = Class.forName("mypackage.MyClass", true, loader);
Class<? extends Runnable> runClass = clazz.asSubclass(Runnable.class);
References:
