Hello,

first of all, please excuse if my English is not the best...

I am trying to manually create a breakpoint in a VM that is launched via the sun.com.jdi.CommandLineLaunch connector. I wish to create this break-point at the start of the main(String[]) method of my Test class. For this, as far as I understand, I need to get the Location of Test.main. However, this is where I fail - I do not see how to create this Location object. I would really appreciate it if one of you could point me into the right direction.

This is the current state of my code:

    public void runDebugSession() {
        // get command line connector from list of available connectors
        Connector connector = null;
        List<Connector> connectors = Bootstrap.virtualMachineManager()
                .allConnectors();
        for (Connector c : connectors) {
            if (c.name().equals("com.sun.jdi.CommandLineLaunch"))
                connector = c;
        }
        // set arguments for this connector.
        Map<String, Connector.Argument> arguments = connector.defaultArguments();
        Connector.Argument main = arguments.get("main");
        Connector.Argument options = arguments.get("options");
        Connector.Argument suspend = arguments.get("suspend");
        main.setValue("mypck.Test arg1");
        options.setValue("-cp {myclasspath}");
        LaunchingConnector launcher = (LaunchingConnector) connector;
        VirtualMachine vm = null;
        try {
            vm = launcher.launch(arguments);
            vm.suspend();
        } catch (Exception e) {
            System.exit(0);
        }
        Process process = vm.process();
 
        EventRequestManager erm = vm.eventRequestManager();
        BreakPointRequest breakPoint = erm.createBreakpointRequest(/* how do I get the correct location? */);
        boolean doLoop = true;
        EventQueue eventQueue = vm.eventQueue();
        vm.resume();
        while (doLoop) {
            EventSet eventSet = null;
            try {
                eventSet = eventQueue.remove();
            } catch (InterruptedException e) {
                e.printStackTrace();
                System.exit(0);
            }
 
            EventIterator eventIterator = eventSet.eventIterator();
            while (eventIterator.hasNext()) {
                Event event = eventIterator.nextEvent();
                if (event instanceof BreakpointEvent) {
                    // handle break point event in here
                }
                vm.resume();
            }
        }
    }

Thank you for your held in advance and best regards,
Bjoern

 

 

Hi Bjoern!

Breakpoints -in general- work for specific code locations. A location is made up from several things.
(0) the type: class or interface
(1) the class
(2) the method
(3) the actual location (code offset) in that method
The JDWP uses a 17byte location array for stuff like that. To ease the whole breakpoint story the JDI offers you all location of a method. See List<Location> allLineLocations() in com.sun.jdi.Method.

Well, you have to take these steps:
(1) Get the reference of a class (hint: ClassPrepareEvent)
(2) Select a method of that class and retrieve the locations
(3) Pick a location and set your breakpoint

Hope that could help you

 

 

Hi Johannes,

thanks for your reply - especially the hint regarding the ClassPrepareEvent. That was exactly what I was looking for.

Best regards,
Bjoern