Can't Instaniate Class

Question

I'm using a C# dll library in my java code, this library functions is called using jna, some of the parameters of these functions contain Structs, and to create an equivalent parameter in Java I have to create a static abstract class which inherits Structure class and it must contains all the variables that exists in the struct that I'm trying to create an equivalent to, for more illustration:

in C#:

struct SDK_AutoConfig {
    int iDay;       
    int iHour;          
    int isec;       
};

and there is a function which is like:

run_auto_config(int x, SDK_AutoConfig auto)

So, to call such function in Java:

// Declaring the Struct
public static abstract class SDK_AutoConfig extends Structure{
    public int iDay;        
    public int iHour;           
    public int isec;
}

// Instantiating it
SDK_AutoConfig auto = new SDK_AutoConfig() {
    @Override
    protected List getFieldOrder() {
        List<Object> list = new ArrayList<>();
        return list;
    }
};

// And to call the function
run_auto_config(65, auto);

tell here everything is OK, but when there is another struct declared as a variable inside the SDK_AutoConfig struct, I can't deal with, what I tried first is to regularly pass it:

public static abstract class SDK_AutoConfig extends Structure{
    public int iDay;        
    public int iHour;           
    public int isec;
    public OTHER_STRUCT struct_two;
}

but when doing that I get:

Exception in thread "main" java.lang.IllegalArgumentException: Invalid Structure field in class Test$1, field name 'struct_two' (class Test$SDK_AutoConfig$OTHER_STRUCT): Can't instantiate class Test$SDK_AutoConfig$OTHER_STRUCT (java.lang.InstantiationException)

So, I tried to instantiate it first then pass it to the constructor of SDK_AutoConfig:

OTHER_STRUCT mStruct = new OTHER_STRUCT() {
    @Override
    protected List getFieldOrder() {
        List<Object> list = new ArrayList<>();
        return list;
    }
};

SDK_AutoConfig auto = new SDK_AutoConfig(mStruct) {
    @Override
    protected List getFieldOrder() {
        List<Object> list = new ArrayList<>();
        return list;
    }
};

// Then, inside the Class
public static abstract class SDK_AutoConfig extends Structure{
    public OTHER_STRUCT struct_two;
    public DeviceDate(OTHER_STRUCT mStruct){
        struct_two = mStruct;
    }
    public int iDay;        
    public int iHour;           
    public int isec;
}

but I got the same exact Exception. So, how to solve that?

Answer 1

Move your anonymous instance creation code into your Structure class and remove the abstract modifier. Then you can nest the different structures however you need to.

As for the C# DLL exported API, as long as your method declarations are decorated with extern "C" and use only C constructs, they should be exported in a compatible manner and thus usable by JNA.