Re: [Jpype-users] Multiple Start and Shutdown

[<je...@le...>]

Thanks Steve for the quick response.

I was hesitant to try building a custom classloader because I wasn't  
sure how that would play with JPype and I don't know enough java to  
debug it.

I'm going to try to avoid the issue by just using a global setting for  
the class path that can be all encompassing. If (when) that doesn't  
suffice I'll try writing my class loader. If I find anything  
interesting I'll try to post it.

Jeremy

Quoting Steve Ménard <men...@gm...>:

> Interesting use case ...
>
> It "should" work, but JVM loading/unloading is an iffy subject at best. All
> those classes that were already loaded using the first JVM instance will
> stay tehre (at least their python counterpart) but not be useable ...
>
> Add to that the enormous overhead of starting.stopping the JVM, and I
> stringly suggest you look into other solutions.
>
> If both your ptyhon modulesa re loaded before the JVM starts, they could add
> their dependencies to a registry of some sort, and then when teh JVM starts
> those dependencies cann be pulled into a single JVM.
>
> Failing that, you could look into using a custom classloader. They are nto
> very ahrd to make, and some of them will allow you to change the classpath
> at runtime. They are nto very ahrd to make (you could even find a ready-made
> one).
> http://kalanir.blogspot.com/2010/01/how-to-write-custom-class-loader-to.htmlgives
> you one simple example.
>
> Steve Menard
>
> ------------------------------
> Programming today is a race between software engineers striving to build
> bigger and better idiot-proof programs, and the Universe trying to produce
> bigger and better idiots. So far, the Universe is winning.
>     Rick Cook, The Wizardry Compiled
> ------
> There are two major products that come out of Berkeley: LSD and UNIX. We
> don't believe this to be a coincidence.
> -- Jeremy S. Anderson
>
>
> On Wed, Apr 13, 2011 at 4:00 PM, <je...@le...> wrote:
>
>> Hi,
>>
>> Suppose I try to do the following
>> startJvm->Shutdownjvm ->startjvm
>>
>> jpype throws an exception "unable to start jvm" when I try to restart the
>> jvm.
>>
>> The reason I'm trying to do this is because I want to make sure the
>> classpath is set a certain way and my understanding is that you can't
>> set the classpath at runtime; so I need to start the jvm and specify
>> the classpath.
>>
>> Here's why:
>> I have two independent functions "funcA" and funcB both of which use
>> jpype to execute java code.  funcA needs  libfunca.jar and  funcb
>> needs libfuncb.jar. I'd like funcA and funcB to be able to start the
>> jvm and execute the approriate java code without forcing funcA/funcB
>> to know about what jars the other one needs to be on the classpath. so
>> funca should only know that libfunca.jar needs to be on the classpath;
>> and should start the jvm with only libfunca.jar on the classpath.
>>
>> Any suggestions how to solve this?
>>
>> Thanks.
>>
>>
>> Jeremy
>>
>>
>>
>> ------------------------------------------------------------------------------
>> Benefiting from Server Virtualization: Beyond Initial Workload
>> Consolidation -- Increasing the use of server virtualization is a top
>> priority.Virtualization can reduce costs, simplify management, and improve
>> application availability and disaster protection. Learn more about boosting
>> the value of server virtualization. http://p.sf.net/sfu/vmware-sfdev2dev
>> _______________________________________________
>> Jpype-users mailing list
>> Jpy...@li...
>> https://lists.sourceforge.net/lists/listinfo/jpype-users
>>
>