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

[Daniel.Boegelein]

Hi,

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 /
jint???

Thanks for every tip/help/hint in advance.

My code is:

C:

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
thread
RXPARAMS prxParams;

prxParams.eventHandle = eventHandle;
prxParams.portHandle = ph;
prxParams.caller = caller;
prxParams.env = env;
prxParams.callBackName = (*env)-

GetStringUTFChars(env,callBackName, 0);

prxParams.callBackOrg = callBackName;


listenCanTest(prxParams);
.......
}

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,
"internalTestCallBack","(IJ)Z");

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");
#endif

}


Java:

public class VectorCanLib implements Runnable{

//Returns the Id of the gen
public synchronized long
registerListener(VectorXlLibraryNotifier
callBack)
{

closeNotify = false;

if(notifyThread == null){
notifyThread = new Thread(this);
notifyThread.start();
}

listeners.add(callBack);

return 0;
}

public void run() {

VectorXLDriverLib.setNotifier(portHandle, queueLevel,
this,
"internalNotifyCallback");

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,
int
queueLevel, Object caller, String callBackName);

static {
try{
System.load(System.getProperty("user.dir") + "\\" +
"MyDll.dll");
}
catch(Exception e) {
e.printStackTrace();
}

}

 

[Gordon Beaton]

jint test = i;
jlong testlong = l;

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

Why are you passing the *address* of test and testlong? Just pass the
values.

/gordon

--

 

[Daniel.Boegelein]

Why are you passing the *address* of test and testlong? Just pass the
values.

/gordon

--

Thx again for your help gordon. I made the changes you suggested.
Unfortunatelly i still receive the wrong values in java. Any ideas?

 

[Gordon Beaton]

Thx again for your help gordon. I made the changes you suggested.
Unfortunatelly i still receive the wrong values in java. Any ideas?

And (I missed this in my previos response) you seem once again to be
passing more arguments than the method is expecting. What is
eventObj.ref doing there?

/gordon

--