Java API: added JNI_OnLoad to eliminate jvm warnings

modules/java/src/cpp/jni_part.cpp

+#include <jni.h>
+
+extern "C" {
+
+JNIEXPORT jint JNICALL
+JNI_OnLoad(JavaVM* vm, void* reserved)
+{
+    JNIEnv* env;
+    if (vm->GetEnv((void**) &env, JNI_VERSION_1_6) != JNI_OK)
+        return -1;
+
+    /* get class with (*env)->FindClass */
+    /* register methods with (*env)->RegisterNatives */
+
+    return JNI_VERSION_1_6;
+}
+
+JNIEXPORT void JNICALL
+JNI_OnUnload(JavaVM *vm, void *reserved)
+{
+  //do nothing
+}
+
+} // extern "C"
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