Halt()?

Spark.halt() is used to stop the rest of the before() and after() filters from being processed. Since we are redirecting somewhere else, there's no further need to process the request and response any further. Although this is the last of 2 before() filters we have now, that may not always be the case. Calling halt() prevents any filters we may add in the future from running necessarily .

You didn't post any code.. So I wont be able to tell you how and why you're using the halt method in your specific situation. But as for what its use is, it is used to forcibly terminate a currently running java virtual machine, and you inherit this method from the Runtime class. The halt method returns nothing and it takes an int 'status' as an argument, a nonzero status code indicates abnormal termination.

Here's a basic example of using the halt method:

public class RuntimePrac {

    public static void main(String[] args) {
        System.out.println("Starting...");

        //halts your process and terminates the currently running JVM.
        Runtime.getRuntime().halt(0);

        //this line of code never runs.
        System.out.println("Still running...");
    }
}

The output is:

Starting...

If you wanna read more about the Runtime class and the halt method, you can find more about it here: https://docs.oracle.com/javase/8/docs/api/java/lang/Runtime.html

Also, if you want me to tell you a little bit more specifics, as to why and how you're using the halt method. You're gonna need to post the code where it's being used.