java - JNINativeInterface_ * is null -

i developing jni application. jninativeinterface_ * inside struct struct jnienv_ null, hence causing call jni (example : env->newstringutf(...)) functions throw segmentation fault error. jnienv_ struct looks :

struct jnienv_ {     const struct jninativeinterface_ *functions; . . . 

i dont know how fix this, think java supposed fill when make call system.loadlibrary(...). appreciate help.

two possibilities:

1) c++ code called java native function:

for example:

jniexport void jnicall java_myjnative_dosomething(jnienv *env, jobject jo) {     std::cout << "dosomething() : "; } 

the jnienv* pointer given java environment.

2) c++ code calls java code via jni:

in case have setup javavm* , jnienv* pointer, following jni invocation logic. see example this article.

a special case mentionned, if have invoked jnienv* work multiple threads on c++ side. every thread has attach jnienv* using:

jnienv *env;                // pointer native interface jint rc = jvm->attachcurrentthread ((void **)&env, nullptr);  // attach without addutiobal parameters                             // jvm valid javavm*