Re: C++ wrapper for java

Jack wrote:


It should be in any good JNI ressource.

Some code attached below.

Arne

================================================

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <jni.h>

void start_java(int maxmem, char *classpath, char *mainclass,int
nargs,char **args)
{
     JavaVMOption options[2];
     JavaVMInitArgs vm_args;
     JNIEnv *env;
     JavaVM *jvm;
     jint res;
    jclass mainclassptr;
    jmethodID mainmethod;
    jobjectArray mainargs;
    jstring *mainargsptr;
     int i;
     char maxmemopt[16];
     char classpathopt[1024];
     char mainclass2[128];
     sprintf(maxmemopt,"-Xmx%dm",maxmem);
     sprintf(classpathopt,"-Djava.class.path=%s",classpath);
     options[0].optionString = maxmemopt;
     options[1].optionString = classpathopt;
     vm_args.version = JNI_VERSION_1_4;
     vm_args.nOptions = 2;
     vm_args.options = options;
    vm_args.ignoreUnrecognized = JNI_FALSE;
     res = JNI_CreateJavaVM(&jvm,(void **)&env,&vm_args);
     if(res<0)
     {
         printf("Error creating JVM\n");
         return;
     }
     strcpy(mainclass2,mainclass);
     for(i=0;i<strlen(mainclass2);i++)
     {
         if(mainclass2[i]=='.')
         {
             mainclass2[i]='/';
         }
     }
     mainclassptr = (*env)->FindClass(env,mainclass2);
     if(mainclassptr==NULL)
     {
         printf("Error finding class %s\n",mainclass);
         return;
     }
     mainmethod = (*env)->GetStaticMethodID(env,mainclassptr,"main",
"([Ljava/lang/String;)V");
     if (mainmethod==NULL)
     {
         printf("Error getting main method in class %s\n",mainclass);
         return;
     }
    mainargs =
(*env)->NewObjectArray(env,nargs,(*env)->FindClass(env,"java/lang/String"),NULL);
     mainargsptr = (jstring *)malloc(nargs*sizeof(jstring));
     for(i=0;i<nargs;i++)
     {
         mainargsptr[i] = (*env)->NewStringUTF(env,args[i]);
         (*env)->SetObjectArrayElement(env,mainargs,i,mainargsptr[i]);
     }
    (*env)->CallStaticVoidMethod(env,mainclassptr,mainmethod,mainargs);
     free(mainargsptr);
     (*jvm)->DestroyJavaVM(jvm);
     return;
}

int main(int argc,char *argv[])
{
     /*
      * java -Xmx128m -classpath test.jar test.Test A BB CCC
      */
     char *args[] = { "A", "BB", "CCC" };
     start_java(128, "test.jar", "test.Test", 3, args);
     return 0;
}