CODEWITHSUNDEEP
java
Errore Fatale
Errore Fatale

Reputation: 988

Create a stoppable java program (daemon)

Starting a java command line application is easy, you only have to write the following line in a command prompt (in the directory where the app is located).

java myApp.java

However, to stop the application in the right way, so that you ensure that all unmanaged resources are cleaned (and anything that must be done before stop, will be done) requires custom code.

The app will run in a debian system with no GUI as a daemon (it will run in background).

Here below I write the skeleton of the code.

public class MainClass {

    public static void main(String[] args) throws Exception {

        boolean stop = false;

        while(!stop){
            doSomething();
        }

        stop();     
    }

    private static void doSomething(){
        //Main code of app here
    }

    private static void stop(){
        beforeStop();

        System.exit(0);
    }

    private static void beforeStop(){
        clean();

        //Code to do anything you have to do before stop
    }

    private static void clean(){
        //Code to clean unmanaged resources
    }

}

As you can see, the app will run 24/24 and won't stop until you don't stop it. Killing the process (as some people suggest) is not a good solution, because (for example) some unmanaged resources might not be cleaned properly.

I need a code which makes possible to alter the boolean variable "stop" from OUTSIDE.

The best solution is the one which makes possible to stop the app with a command similar to the start command, see pseudo code below (executed in a command prompt, in the directory where myApp.java is located).

myApp.java stop=true

But if it's not possible, the second option would be to have an other java command line app, which stops myApp.java, so that I could stop myApp.java with the following code

java stopMyApp.java

Is someone able to suggest a useful code example?

Upvotes: 0

Views: 147

Answers (1)

Paco Abato
Paco Abato

Reputation: 4065

You can use a text file with one word. Your program reads it every x seconds and depending on that word it will autostop.

You can change the file text content by hand or with another program you can run whenever you want.

Even better you can use WatchService API (Java 7) or VFS API from Apache Commons to be notified when the file changes.

If you use a DB you can use it instead of a plain file.

Upvotes: 1

Related Questions