JNI: Calling Java From C (with Long and integer as parameters)

17 Apr 2007 02:34:00 -0700

after i've finally solved my last jni problems with stirngs, i've ran
into another one. But now my problem should be a little bit easier ;)

What i want to do ist to call a Java Function From C. The Java
Function expects an int value and a long value as parameters. My
Problem is how to set the long and the int value. I never get the
right values in java. Must i convert the long and int into jlongs /

Thanks for every tip/help/hint in advance.

My code is:


struct RxParams
    XLhandle eventHandle;
    long portHandle;
    const char *callBackName;
    jobject caller;
    JNIEnv *env;
    jstring callBackOrg;
}typedef RXPARAMS;

struct javaObject
        jobject ref; //reference to the java object
        jclass jcls; //class id of the java obj
}typedef JAVAOBJECT;

JNIEXPORT jlong JNICALL Java_VectorXLDriverLib_setNotifier(JNIEnv
*env, jclass jcls, jobject portHandle, jint queueLevel , jobject
caller, jstring callBackName)

   //reserve and set the structure which is passed to the listener
   RXPARAMS prxParams;

       prxParams.eventHandle = eventHandle;
       prxParams.portHandle = ph;
       prxParams.caller = caller;
       prxParams.env = env;
       prxParams.callBackName = (*env)-
GetStringUTFChars(env,callBackName, 0);
   prxParams.callBackOrg = callBackName;


void listenCanTest(RXPARAMS par)
  writeLog("In RxThread\n");
    unsigned int msgsrx = RECEIVE_EVENT_SIZE;
        jsize count;
    jmethodID jmid;
    jclass icls;
    jboolean continueListening = 1;

    char string[50];
    JAVAOBJECT eventObj; //object used for callBack to java

    RXPARAMS prxParams = par;

    JNIEnv *env = par.env;

   writeLog("Before get Structure XLCANEvent\n");
    // Klasse des aufrufenden Java Objektes ermitteln:
     icls = (*env)->GetObjectClass(env, prxParams.caller);

    writeLog("before getMID: icls: %02x\n", icls);
        jmid = (*env)->GetMethodID(env, icls,

    writeLog("after getMID\n");
    if (jmid == 0){
        writeLog("jmid == NULL\n");

       int i = 10;
      int l = 15;

   jint test = i;
   jlong testlong = l;

 continueListening = (*env)->CallBooleanMethod(env, prxParams.caller,
jmid, eventObj.ref, &test, &testlong);

#ifdef DEBUG
    writeLog("Listener has been terminated");



public class VectorCanLib implements Runnable{

        //Returns the Id of the gen
        public synchronized long

                closeNotify = false;

                if(notifyThread == null){
                        notifyThread = new Thread(this);


                return 0;

        public void run() {

                VectorXLDriverLib.setNotifier(portHandle, queueLevel,

                System.out.println("Internal notifier closed");

      private synchronized boolean internalTestCallBack(int i, long l)
        System.out.println("I: " + i + "L: " + l);

        return true;


public abstract class VectorXLDriverLib{


        public static native long setNotifier(XLPortHandle portHandle,
queueLevel, Object caller, String callBackName);

        static {
                System.load(System.getProperty("user.dir") + "\\" +
        catch(Exception e) {


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