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Angel Montes de Oca
Asked: 2020-07-27 14:00:58 +0800 CST 2020-07-27 14:00:58 +0800 CST

Use JNA to access a DLL (C#) function from Java?

  • 772

I have one DLL( TransferImg.dll) that is written in C#(provided by an external company), which they tell me that I need to create an interface to access image transmission functions from JAVA, I have been investigating how, but I have not found something that understands or works.

The data provided to me is: - TransferImg.dll library
- Add reference to project.
- Add Using Transfer;
- Create Object Command myobj = new Command();
- Call the function myobj.SendImagesToScalewhich returns an integer with the error.

This is the function I want to use:

int SendImagesToScale(string Ip, string PathImage ,string Tipo, Socket iSock);

I don't have a clear idea how to do it, this is my code taken from an example:

public class SendImg {
    public interface CLibrary extends Library {
        CLibrary INSTANCE = (CLibrary)
            Native.loadLibrary((Platform.isWindows() ? "C:\TransferImg.dll" : "c#"),                                   CLibrary.class);

        void SendImagesToScale(string Ip, string PathImage ,string Tipo, Socket iSock);
    }

    public static void main(String[] args) {
        CLibrary.INSTANCE.SendImagesToScale("192.168.1.111", "C:\img.jpg", "Splash", 3306);

    }
}

Dll: TransferImg.dll

java

3 Answers

  1. Best Answer

    I just created a test project in c# and added the DLL you uploaded to the created project.
    And when inspecting the dll the function does not exist int SendImagesToScale(string Ip, string PathImage ,string Tipo, Socket iSock);as such but there is a similar one that is this:int TORREYSendImagesToScale(String sIpScale, String sPathImage, String sTypeData, Socket iSock);

    The problem is that if you want to use it you cannot do it directly since this is a function of a class and the function is not declared as static so you must first create an instance of the class and then call the function through the created instance .

    TorreyTransfer.CommandTorrey commandTorrey = new TorreyTransfer.CommandTorrey();
commandTorrey.TORREYSendImagesToScale("IpScale", "pathImage", "TypeData", "UnSocket");

    enter image description here

    • 4

  2. Check the dll and I didn't find any function void SendImagesToScale(string Ip, string PathImage ,string Tipo, Socket iSock);but if there is one int TORREYSendImagesToScale(String sIpScale, String sPathImage, String sTypeData, Socket iSock);that may be your mistake, decompile the dll with dotpeek ( https://www.jetbrains.com/decompiler/download/ ) so you can study the dll more or go back to do it to your liking, well that way I could see all the code inside the dll, in the namespace of TorreyTransfer is the function TORREYSendImagesToScale.

    I made a bit of code that could help you:

    import java.net.Socket;
import com.sun.jna.Library;
import com.sun.jna.Native;

public class Main {

    private final static int PUERTO = 1234;
    private final static String HOST = "localhost";
    protected static Socket mysocket;

    public interface MyObject extends Library {
        //sIpScale=ip de destino de la imagen
        //sPathImage= path de la imagen a enviar
        //sTypeData=varia entre "Splash", "TestUsb","Product" y "TestSdcard"
        //iSock= socket de conexion de tu aplicacion

        int TORREYSendImagesToScale(String sIpScale, String sPathImage, String sTypeData, Socket iSock);
    }

    public static void main(String[] args) {
        try {
            mysocket = new Socket(HOST, PUERTO);
            MyObject myObj = (MyObject) Native.loadLibrary("TransferImg.dll", MyObject.class);
            int resultado = myObj.TORREYSendImagesToScale("192.168.1.111", "C:/img.jpg", "Splash", mysocket);
            //resultado = {0=correcto windows}, otros datos error
        }
    }
}

    Where TransferImg.dllit should be in the address of your project.

    • 2

  3. You need to make several wrappers, call a class that calls a class that calls your DLLen C#, an example is:
    enter image description here

    Here you have a page that could be of great help: LINK

    • 2