Re: [Jython-users] Using Jython as an interactive Java debugger.

[Paul G. <pau...@so...>]

I am currently have a side project that will do something like this. It =

is a module that implements a telnet daemon that runs as a java thread. =

When someone connects, it starts a jython interpreter and uses this as=20
the shell for user interaction. Thus, if this is embedded in a running=20
server, you can connect using an ordinary telnet client and manipulate=20
object running in the same VM. This is still work in progress, but some =

of the sticky points so far:

   - Implementing telnet: I tried to find a java telnet daemon that I=20
could adapt or borrow code from. There does not seem to be any yet. Also=
=20
getting complete and understandable documentation for the telnet protoco=
l=20
is not that easy (every time I use a new telnet client, it starts trying=
=20
to negotiate some other connection parameter that i cannot find in any=20
documentation).

   - There has to be a way to get references to the other objects that=20
you want to manipulate. This can be as simple as placing references to=20
all of the objects that you want to manipulate into a hashtable that is =

statically initialized or available through a singleton. It just need to=
=20
be done in advance, otherwise the jython interpreter winds up more or=20
less isolated from the rest of the application.

   - If I try to run multiple instances of jython interpreters in=20
different threads, bad things start to happen. It is not really critical=
=20
that I handle multiple connections simultaneously, but I would not expec=
t=20
this to be a problem. :-(


AFAIK it is also possible to remotely connect to a running VM using the =

Java debugging API (if the VM was started with debugging options on), so=
=20
if you go this route, you do not need to provide your own interpreter in=
=20
that VM, but jython might be helpful in making a simple client.

The idea of the project above is to do more high level interaction, like=
=20
reconfiguration, at runtime.

-Paul



> I am experimenting with Jython at the moment. I am impressed.

> I was wondering if any jython-guru's have used it to debug Java code.

> I guess you could run the Jython interpretor in a seperate thread to t=
he
> program you're trying to debug. You could then stop the thread from=20
jython
> and inspect the state of its attributes and test calling some of the
> methods.

> This would be very handy for experimenting with swing gui's.

> Has anybody experimented with some of the Java debugger api's? It may =

even
> be possible to set break points on particular methods.

> Any Ideas would be appreciated.

> Thanks,
> Greg.