How do I "convert" a jobject class to a complex C++ type?

Question

I have a Java class that matches a C++ class. The java class is named SDClass_JNI and the C++ class is called SDClass. I pass the Java class as a jobject param to my JNI method. In that JNI method, I want to then convert that jobject passed in as a param in my JNI method to the "matching" C++ method. (e.g. SDClass_JNI -> SDCLass). How can I do this?

Answer 1

If I understand correctly you want an implicit conversion from java class to corresponding c++ class.

This is not possible, you should write code to handle the marshaling process.

Something like:

SNDClass toSND(JNIEnv *env, jobject obj) {

    SNDClass result;

    jclass cls = env->FindClass("com/.../SDClass_JNI");
    checkException(env);
    //TODO release jclass object (env->DeleteLocalRef(cls);)(maybe use some sort of scoped smart pointer )

    jmethodID mid = env->GetMethodID(mCls, "getField1", "()D");
    checkException(env);
    jdouble value = env->CallDoubleMethod(obj, mid);
    checkException(env);
    result.setField1(jdouble);
    .....
}

void checkException(JNIEnv *env)
{
    jthrowable exc = env->ExceptionOccurred();
    if (NULL == exc)
    {
        return;
    }
    //TODO decide how to handle
}