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From Daniel Julin <...@us.ibm.com>
Subject Re: System Properties and Env vars
Date Tue, 12 Jan 2010 02:38:34 GMT

For what it's worth, the DTFJ-based DumpAnalyzer tool also has a module for
extracting system properties: com.ibm.dtfj.analyzer.jvm.SystemProperties.
It works by using DTFJ API calls to find the java.lang.System class
instance in the list of classloaders, then traverse it, then interpret the
fields in the java.util.Properties instance that it finds there.

This is one of about 100 "utility" modules that have been built on top of
DTFJ to facilitate the implementation of various common functions in
DumpAnalyzer. I think that this may demonstrate that there are too many
"common functions" and variations to hard-wire into a single low-level API.
We really do need a low level API _and_ a powerful library on top of it.
Similar to how in the runtime, we have the "low-level" JVM and a powerful
class library on top of it... I guess this is similar to the "commons"
library that Steve mentions below?

Incidentally, this simple example of a module for system properties is not
as simple as it sounds. In a complex J2EE or OSGI world with a complex
hierarchy of classloaders, we can't be sure that there will always be a
single definition of java.lang.System, or of other similar classes that
hold similar properties associated with various J2EE or OSGI modules. If
that's the case, we would need to have an equivalent collection of analysis
modules that deal with these variations.


As for environment variables, I have not looked in Kato recently, but in
DTFJ, they used to be available, but from the ImageProcess, not from the
JavaRuntime.



-- Daniel --

==============================================================
Daniel P. Julin
Senior Technical Staff Member
Technical Area Lead  -  IBM AIM WebSphere Serviceability Team

EMail: dpj@us.ibm.com
Phone: 347-273-2093          Tie-line 930-3468
Notes: Daniel Julin/Pittsburgh/IBM@IBMUS



Steve Poole <spoole167@googlemail.com> wrote on 2010-01-11 11:23:53 AM:

> [image removed]
>
> Re: System Properties and Env vars
>
> Steve Poole
>
> to:
>
> kato-spec
>
> 10-01-11 11:24 AM
>
> Please respond to kato-spec
>
> On Mon, Jan 11, 2010 at 4:19 PM, David Griffiths
> <david.griffiths@gmail.com>wrote:
>
> > Agreed about the system properties (as a Map). Env vars used to be
> > available via ImageProcess but I guess you want to move away from
> > that?
> >
> > I would like have the same data available from the JavaRuntime   for
> completeness since java.lang.System  provides both properties and envvars
> and , as you've guessed,  because the ImageProcess might not be
available.
>
>
>
> Cheers,
> >
> > Dave
> >
> > On Mon, Jan 11, 2010 at 3:21 PM, Steve Poole <spoole167@googlemail.com>
> > wrote:
> > > Is it just me or does anyone else think its an unneccessary
restriction
> > that
> > > the JavaRuntime API does not offer the ability to get to System
> > Properties
> > > or Environmental variables?  You can get them from a running JVM so
why
> > > should we not have the same capability on our API?
> > >
> > >
> > > --
> > > Steve
> > >
> >
>
>
>
> --
> Steve
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