JVM crashes when converting jstring to native string

Question

Hi ,
I am trying to convert a jstring to a char * . My main program is in C.
I tried calling the two methods :
const char str = (env)->GetStringUTFChars(env, myJstring, 0);
and
const char *result = JNU_GetStringNativeChars(env, myJstring);
Both the times the VM crashed. I copied the code for both the above mentioned functions from sun's website examples.
Any help appreciated.
thanks,
Sanjay

Answer 1

Try this:
JNIEXPORT void JNICALL my_native_method
  (JNIEnv * env, jobject obj, jstring jnewValue)     
  jboolean isCopy;
  const char* newValue = env->GetStringUTFChars(jnewValue, &isCopy);
  // release string if possible
  if(isCopy == JNI_TRUE) {
    env->ReleaseStringUTFChars(jnewValue, newValue);
} But be aware of one thing:
The JNIEnv pointer has to be valid in the current thread, if not the JVM will crash. The JNIEnv pointer is always valid in the example above, since this is the implementation of a native method. The JNIEnv is only valid in the thread it is created in.
Hope this can be of any help :)