create an object with cni

create an object with cni

[Bucher Fabio]

Hi

I just have a simple programm: One Java class, one C++ class.

Java:
public class Java_with_CNI {

    public Java_with_CNI(){
    }

    public void printHello(){
        System.out.println("Hallo Du, ich wurde durch CNI aufgerufen");
    }
}

and my C++ class:
#include <gcj/cni.h>
#include "Java_with_CNI.h"

class Hallo{
    int main(){
        Java_with_CNI test = new Java_with_CNI::Java_with_CNI();
        test.printHello();
        return 0;
    }
};


This is my first time i use C++, so I dont know whats wrong with my class. I just want to create a new Object (Java_with_CNI) and call the printHello()-method.
What is wrong with my class?

Thank you for your help and best regards
Fabio Bucher

Re: create an object with cni

[Bryce McKinlay]

Fabio,

You need to initialise Java by calling "JvCreateJavaVM(NULL);" before
making calls from C++ into Java code.

See the CNI documentation (§ 11.16.2) for a complete example:
http://gcc.gnu.org/onlinedocs/gcj/Invocation.html#Invocation

Bryce

On Mon, Jun 24, 2013 at 10:37 AM, Bucher Fabio <fabio.bucher@ntb.ch> wrote:
> Hi
>
> I just have a simple programm: One Java class, one C++ class.
>
> Java:
> public class Java_with_CNI {
>
>     public Java_with_CNI(){
>     }
>
>     public void printHello(){
>         System.out.println("Hallo Du, ich wurde durch CNI aufgerufen");
>     }
> }
>
> and my C++ class:
> #include <gcj/cni.h>
> #include "Java_with_CNI.h"
>
> class Hallo{
>     int main(){
>         Java_with_CNI test = new Java_with_CNI::Java_with_CNI();
>         test.printHello();
>         return 0;
>     }
> };
>
>
> This is my first time i use C++, so I dont know whats wrong with my class. I just want to create a new Object (Java_with_CNI) and call the printHello()-method.
> What is wrong with my class?
>
> Thank you for your help and best regards
> Fabio Bucher
>
>
>
>

create an object with cni

[Bucher Fabio]

Thank you very much!

It works fine.

Best regards and have a nice week
Fabio Bucher

Re: create an object with cni

[Bryce McKinlay]

On Mon, Jun 24, 2013 at 1:17 PM, Bucher Fabio <fabio.bucher@ntb.ch> wrote:
> Thank you, I can run this example and I put my code in there. Which is the right namespace to use, and which Class do I have to load with the JvInitClass()-method?

The namespace corresponds directly to the package name in Java. e.g.
"java.util" becomes "java::util". If your java class has no package
name then you don't need any namespace.

> Now the error message says:
> Test.cc:20:29: error: expected primary-expression before »)« token
> Test.cc:21:29: error: typ specification expected
> Test.cc:21:29: error: Java-object test is not with new allocated
> Test.cc:21:29: error: »,« or »;« expected
>
> Do I have to load my Java-class with the JvInitClass()-method? I think yes, but how is it done the right way?

Actually, no, you don't need to bother with JvInitClass in this case,
because calling "new" will ensure that it is initialised
automatically. The example only needs the JvInitClass() call because
it is accessing a static Java variable, System.out.

The correct syntax to reference your class would be:

&Java_with_CNI::class$  (This is the CNI equivalent of
"Java_with_CNI.class" in Java.)

Bryce

create an object with cni

[Bucher Fabio]

Thank you, I can run this example and I put my code in there. Which is the right namespace to use, and which Class do I have to load with the JvInitClass()-method? Now the error message says:
Test.cc:20:29: error: expected primary-expression before »)« token
Test.cc:21:29: error: typ specification expected
Test.cc:21:29: error: Java-object test is not with new allocated
Test.cc:21:29: error: »,« or »;« expected

Do I have to load my Java-class with the JvInitClass()-method? I think yes, but how is it done the right way?


#include <gcj/cni.h>
#include "Java_with_CNI.h"
#include <java/lang/System.h>
#include <java/io/PrintStream.h>
#include <java/lang/Throwable.h>

        int main(int argc, char *argv[]){
                using namespace java::lang;
                //using namespace ::Java_with_CNI;
                try{
                        JvCreateJavaVM(NULL);
                        JvAttachCurrentThread(NULL, NULL);
                        JvInitClass(&System::class$);
                        String *message = JvNewStringLatin1("Hello from C++");
                        System::out->println(message);


                       /* Here goes my Code */
20                      JvInitClass(Java_with_CNI);
21                      Java_with_CNI test = new Java_with_CNI::Java_with_CNI();
                        test.printHello();


                        JvDetachCurrentThread();
                }catch(Throwable *t){
                        System::err->println(JvNewStringLatin1("Unhandled Java exception:"));
                }
                //rtems_entry_point(void);
                //return 0;
        }