JNI communiction using a Java and a C++ Thread

Question

Hi,
My purpose is to run a Java and a C++ thread parallel.
The C++ thread receives events from a hardware. Getting an event it should put this (for testing it is just a String ) to a Java method (there the events will be collected in a vector).
The Java thread should compute these vector step by step when it is scheduled.
Therefore I have a Java Thread that invokes a native method.
This C++ method
1. stores a refernece to the JavaVM in a global var (using env->getJavaVM ),
2. stores the object (given by JNICall) in a global var (reference to the calling java object),
3. creates an object dynamically (this implements a Runnable C++ Interface needed for my Thread structure)
4. and creates (dynamically) and starts a C++ Thread ( that uses the Win API ) giving it the former created object as parameter.
Following the C++ thread uses the former stored global JavaVM to get a JNIEnv. It also uses the global stored object.
After this I prepare for executing a callback to Java, e.g. AttachCurrentThread, GetObjectClass, GetMethodID and so on. Finally I sucessfully start some callbacks to Java (in the while loop of the thread).
Now here is my Problem:
The described way only works for a few calls and then raises an error. "java.exe hat ein Problem festgestellt und muss beendet werden." (german os) (In english it should be: "java.exe has detected a problem and has to be determined").
What is wrong with my idea. It is something with the scope of my dynammically created objects? If have no idea anymore.
Here the source code (C++ part):
#include <jni.h>
#include "benchmark.h"
#include "bench.h"
#include "canMessage.h"
JavaVM *jvm;
jobject javaObject;
JNIEXPORT void JNICALL Java_Benchmark_startBench(JNIEnv *env, jobject obj, jobject obj2){
     env->GetJavaVM(&jvm);
     javaObject = obj2;
     cout << "\n C++ Starting benchmark\n\n";
     Benchmark *bm = new Benchmark();
     Thread *thread = new Thread(bm);
     thread->start();
     //thread->join(); //uncomment this there will be no error but also
                                     // no java thread doing it's job
Benchmark::Benchmark(): _continue(false) {
Benchmark::~Benchmark(){
unsigned long Benchmark::run(){
     _continue = true;
     JNIEnv *jniEnv;
        jvm->AttachCurrentThread((void **)&jniEnv, NULL);
        jclass javaClass = jniEnv->GetObjectClass(javaObject);
     if(javaClass == NULL){
          cout << "--> Error: javaClass is null";
     jmethodID methodId = jniEnv->GetMethodID(javaClass, "addMessage", "(Ljava/lang/String;)V");
     if(methodId == NULL){
          cout << "--> Error: methodId is null";
     string str ("This is a test text.");
     const char *cStr = str.c_str();
     jstring javaString = jniEnv->NewStringUTF(cStr);
     jniEnv->CallVoidMethod(javaObject, methodId, javaString );
     int i_loopCount = 0;
     while(_continue){
          i_loopCount++;
          cout << i_loopCount << " C++ runing\n";
          jniEnv->MonitorEnter(javaObject);
          jniEnv->CallVoidMethod(javaObject, methodId, javaString );
          jniEnv->MonitorExit(javaObject);
          canMessage = new CANMessage();
          delete canMessage;
          canMessage = NULL;
     return 0;
void Benchmark::stop(){
     _continue = false;
}Is there a better and more elegant way to solve my problem?
Thanks!

Answer 1

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