How to convert string to jstring in jni.
We can use JNIEnv function.
NewStringUTF Let's see example.

JNIEXPORT jstring JNICALL Java_org_cocos2dx_cpp_AppActivity_text(JNIEnv *env,jobject thiz)
{
    // get scene extend class
    MenuScene* scene = dynamic_cast(cocos2d::CCDirector::sharedDirector()->getRunningScene()->getChildByTag(MenuScene::TAG));
    // convert jstring use NewStringUTF
    return (env)->NewStringUTF(scene->getString.c_str());
}
		

In example.Funtion return jstring.
scene class object function getString return std::string.
I use JNIEnv NewStringUTF return jstring from string const char