Watching all fields that are in scope using JPDA

Question

Hi,
I'm helping develop a debugger using JDI and have a question about watching certain types of variables that are in scope.
I can watch local variables by getting the current thread's StackFrame and can watch static fields of outer classes by getting their corresponding ReferenceTypes. However, I can't find a good way to watch non-static fields of outer classes that aren't shadowed.
Example. Debugging the following code:
class A {
int x = 5;
class B {
public void foo() {
System.out.println("x = " + x);
public void callFoo() {
B myB = new B();
myB.foo();
The result of calling callFoo on an instance of A is "x = 5" as it should be.
Clearly the method foo() can see what x is. However, it seems to me that to watch the value of x (a non-static field) at any point while I'm debugging, I have to have use the thisObject() method of the appropriate StackFrame and then call getValue() with x. However, if my current thread is suspended within the foo() method, it may not always be possible to retrieve the correct StackFrame (e.g. if foo() is called from some other class such as my debugger event handling thread).
Basically, it'd be nice if you could point out that I'm just not seeing some nice call like getValue(Field f) that will get the value of an instance field that is anywhere in scope, especially those in outer classes. Or if you see anything I'm missing or another way to watch instance fields in outer classes, your help would be greatly appreciated!
James

Answer 1

I'm helping develop a debugger using JDI and have a
question about watching certain types of variables
that are in scope.You would do this by creating a com.sun.jdi.request.WatchpointRequest
and restricting the scope of the request to the object specified. This
is done by adding filter(s) to the request before it is enabled. For
more information, take a look at:
http://java.sun.com/j2se/1.4.1/docs/guide/jpda/jdi/com/sun/jdi/request/WatchpointRequest.html#addInstanceFilter(com.sun.jdi.ObjectReference)