callback.c

How to run: 1. compile Callback.java 2. compile the native code into a shared lib cl /Ie:j2sdk1.4.0i

#include <stdio.h>
#include <jni.h>

JNIEXPORT void JNICALL 
Java_Callback_nativeMethod(JNIEnv *env, jobject obj)
{
  jstring str = (*env)->NewStringUTF(env, "zongrui");
  jclass cls = (*env)->GetObjectClass(env, obj);
  jmethodID mid = (*env)->GetMethodID(env, cls, "callback", "(Ljava/lang/String;)V");
  if (mid == 0) {
    return;
  }
  printf("In C about to enter Java.\n");
  (*env)->CallVoidMethod(env, obj, mid, str);
  printf("In C back from Java.\n");
}