Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder2.enfer-du-nord.net!news.cgarbs.de!news.addix.net!feed.news.schlund.de!schlund.de!news.online.de!not-for-mail
From: Philipp Kraus <philipp.kraus@flashpixx.de>
Newsgroups: comp.lang.java.programmer
Subject: Re: JNI generic type of jobject
Date: Tue, 4 Oct 2011 14:49:02 +0200
Organization: 1&1 Internet AG
Lines: 56
Message-ID: <j6evbu$mmq$1@online.de>
References: <j6etsu$lkf$1@online.de> <4e8afbde$0$2529$e4fe514c@news2.news.xs4all.nl>
NNTP-Posting-Host: p3ee2964c.dip0.t-ipconnect.de
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
X-Trace: online.de 1317732542 23258 62.226.150.76 (4 Oct 2011 12:49:02 GMT)
X-Complaints-To: abuse@einsundeins.com
NNTP-Posting-Date: Tue, 4 Oct 2011 12:49:02 +0000 (UTC)
User-Agent: Unison/2.1.5
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:8520

On 2011-10-04 14:28:14 +0200, Silvio said:

> On 10/04/2011 02:23 PM, Philipp Kraus wrote:
>> Hello,
>> 
>> I use JNI calls for some Java classes. Some Java classes are generic
>> classes like:
>> 
>> class mytestclass<T> {
>> 
>> public native void mymethod();
>> 
>> }
>> 
>> The stub shows:
>> 
>> JNIEXPORT void JNICALL Java_mytestclass_mymethod(JNIEnv* p_env, jobject
>> p_object)
>> 
>> How can I get from the jobject which object type is the generic
>> parameter T? Because I would
>> like to create different codes if I do something like:
>> 
>> mytestclass<int> x = new mytestclass<int>();
>> x.mymethod();
>> 
>> mytestclass<String> x = new mytestclass<String>();
>> x.mymethod();
>> 
>> Thanks
>> 
>> Phil
>> 
>> 
> 
> No such thing is possible. Generics are a compile time thing. At 
> runtime only the raw types are available.

Why? jobject is a pointer to the Java object that calls the JNI 
function, JNIEnv is also a pointer to the running
environment, so I should get the type of the generic parameter, because 
the runtime / object knows them
so within the JNI call the parameter must exists.

I can also run in the Java class T.getClass().getName() and the Java 
code returns the name of the type
the JNI call should do the same like  JNIEnv->GetObjectClass( 
jobject.getTemplateVar(0) ) but I need
the name / call of the "getTemplateVar(int)" function which gets an 
object to the first template parameter
of the Java object

Thanks

Phil