How can I abnormally shut down Java application with its own code?

Question

As far as I understand by using System.exit() application shuts down grafecully. But I want a abnormal shut down.

How can I achieve this with java code?

Why? What would you define as "abnormal shut down" and what benefit do you want to gain from this? This sounds like an [XY problem](https://xyproblem.info). — Joachim Sauer, Oct 30 '20 at 12:57
@JoachimSauer I just wanna test kubernetes healtcheck behaviour when application crashed by using a simple endpoint. (I will send /killMyApp request to java application and then check what happens in kubernetes) — H.Ç.T, Oct 30 '20 at 13:10
You could try accessing the current Java process PID ( https://stackoverflow.com/questions/35842/how-can-a-java-program-get-its-own-process-id ) and then using `Runtime.getRuntime().exec` to execute `kill -9`? That's about as abnormal a termination as I can think of but I'm not even remotely sure if that's going to work — Jeroen Steenbeeke, Oct 30 '20 at 13:55

score 2 · Answer 1 · answered Oct 30 '20 at 12:58

2

The System.exit() method takes a status code parameter. A non-zero value status code is used for abnormal termination.

What you want to achieve can be done with System.exit(1).

answered Oct 30 '20 at 12:58

Manaus

407
5
9

1

I think he meant a shutdown that doesn't execute shutdown actions, as if by a crash – Mark Jeronimus Oct 30 '20 at 14:16
@MarkJeronimus just like that – H.Ç.T Oct 30 '20 at 14:20

Mark Jeronimus · Accepted Answer · 2020-10-31T01:02:24.033

You could search for bugs that crash the JVM and aren't fixed. For example I found this "user error" bug https://bugs.openjdk.java.net/browse/JDK-8225643 and it works (i.e. crashes) in my case (openjdk 11.0.9 2020-10-20).

import java.lang.reflect.Field;

import sun.misc.Unsafe;

public final class Temp {
    public static void main(String... args) throws Exception {
        int a = 5;
        int b = 10;
        System.out.printf("a: %s, b: %s\n", a, b);
        swap(addressOf(a), addressOf(b), Integer.BYTES);
        System.out.printf("a: %s, b: %s\n", a, b);
    }

    @SuppressWarnings("unchecked")
    public static <T> long addressOf(T t) throws NoSuchFieldException, IllegalAccessException {
        T[]    arr         = (T[])new Object[]{t};
        Unsafe unsafe      = getUnsafe();
        long   baseOffset  = unsafe.arrayBaseOffset(Object[].class);
        int    addressSize = unsafe.addressSize();
        long   objectAddress;
        switch (addressSize) {
            case 4:
                objectAddress = unsafe.getInt(arr, baseOffset);
                break;
            case 8:
                objectAddress = unsafe.getLong(arr, baseOffset);
                break;
            default:
                throw new Error("unsupported address size: " + addressSize);
        }

        return (objectAddress);
    }

    public static void swap(long addr_1, long addr_2, long bytes) throws NoSuchFieldException, IllegalAccessException {
        Unsafe unsafe = getUnsafe();
        if (unsafe == null) {
            System.out.println("Cannot swap variables!");
            return;
        }
        long allocateMemory_var1 = unsafe.allocateMemory(bytes);

        unsafe.copyMemory(addr_1, allocateMemory_var1, bytes);

        unsafe.copyMemory(addr_2, addr_1, bytes);

        unsafe.copyMemory(allocateMemory_var1, addr_2, bytes);

    }

    private static Unsafe getUnsafe() throws NoSuchFieldException, IllegalAccessException {
        Field f = Unsafe.class.getDeclaredField("theUnsafe");
        f.setAccessible(true);
        return (Unsafe)f.get(null);
    }
}

(I don't know why the code is that long; I just copied it from the bug report and made it compile-able)

Thank you so much. My application crashes perfectly as I wanted :) — H.Ç.T, Oct 30 '20 at 15:46

How can I abnormally shut down Java application with its own code?

2 Answers2