Re: Java Reflection with local variables

Patricia Shanahan <>
Sat, 15 Mar 2008 17:49:08 -0700
ash wrote:

On Mar 15, 7:20 pm, Mark Space <> wrote:

ash wrote:

Hello ,
 I have just been introduced to java reflection , and i understand i
could reflect Classes basic information like methods, constructors,
and fields. But i would like to further reflect local variables ( say
local variables in methods). How could i do that with java reflection
api ? If it cant be done using java reflection api a hint about how it
could be done would be greatly appreciated :D

Local variables don't belong to classes, they belong to threads. You'd
need some sort of stack trace or thread dump to access local variables.
  I don't see such a facility in the Thread classs.

JMX might get you what you want. It is basically a "debugger" tool,
allowing you to poke at a running JVM and it's application.



Thanx for your reply , but i have 2 questions for you though. What do
you mean local variables belong to threads ? If i am write a new class
and im defining some variables , methods or any other stuff. these
elements belong to this class. And second Im checking out JMX now but
it looks too complicated for what i want to accomplish. What i need is
an API to access a running Class information ( methods, fields, local
variables, while loops, for loops , any other thing defined in that

I would put it slightly differently, and say that local variables belong
to method activations. Every method activation happens in some thread.
However, because of recursion there can be several activations of the
same method in the same thread. There is a set of local variables for
each activation.

I agree with the idea that you need to look at this as a debug type of
operation, processing stack frames, rather than as reflection.

Can you explain at a higher level what you are trying to do?


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