//Before wrapper

jclass someClass;
jmethodID someMethod;

void initJNIStuff()
{
        JNIEnv* env = get the environment;
        someClass = env->NewGlobalRef(env->FindClass("some class name"));
        //takes string returns string
        someMethod = env->GetStaticMethodID(someClass, "some function name", "(Ljava/lang/String;)Ljava/lang/String;");
}

void callMyJavaMethod(const std::string& someString)
{
        JNIEnv* env = get the env;
        jstring transformedString = env->NewStringUTF(someString.c_str());
        jstring resultString = (jstring)env->CallStaticObjectMethod(someClass, someMethod, transformedString);
        const char* cStr = env->GetStringUTFChars(resultString, 0);
        env->ReleaseStringUTFChars(resultString, cStr);
}

//After wrapper

JFunction<JString(JString)> someFunction;

void initJNIStuff()
{
        someFunction.LinkStatic("some class name", "some function name");
}

void callMyJavaMethod(const std::string& someString)
{
        std::string resultString = someFunction(someString);
}