Tool to trace which method is currently being executed by JVM in an application?

Question

I have to understand a old, large java code base not written by me.

To track any flow, If I know any class which gets called in that flow, I throw an Exception (like below) to get a stack trace to console, to understand which methods called so far and continue further.

        try {
            throw new Exception();
        } catch (Exception e) {
            e.printStackTrace();
        }

This helps me some extent, But I am completely blind about other flows, where I don't know entry/middle/exit points in that flow.

I am wondering is there any tool or mechanism which tells what JVM is currently executing?

Mine is embedded application. I cant debug in eclipse. I want something which tells what JVM is currently running — Bhargav Kumar R, Jul 29 '16 at 06:46
Do you have network connectivity with the device and what kind of JVM is it running? Debugging over TCP can be an option — Joni, Jul 29 '16 at 06:50
I have network connectivity and can live monitor the console logs. — Bhargav Kumar R, Jul 29 '16 at 06:55
Do you have control over how the JVM is started? http://stackoverflow.com/q/975271/318758 — Joni, Jul 29 '16 at 07:00
You can add a thread to take regular snapshots of the stack trace if you like. Are you saying there is no way to run this Java code on your PC? that would concern me a lot — Peter Lawrey, Jul 29 '16 at 12:12
@Joni Sorry for late reply.. I dont have TCP connection, I have only serial port access to the device. Debugging over serial port possible? — Bhargav Kumar R, Aug 05 '16 at 10:34

score 0 · Answer 1 · answered Aug 27 '16 at 13:17

If you want to understand what threads in the JVM are doing, you can capture a thread dump by kill -3 pid and watch the stdout, or by using jconsole. You can capture a few dumps which is a few seconds far from each other, such that you can feel how the 'current' function moves from one place to another.

If you want to trace/log and understand what values coming and out of your functions, you can use Jackplay.

Tool to trace which method is currently being executed by JVM in an application?

1 Answers1