Java JNI: use a c# dll?

Question

Hi there, I am working on a Windows XP machine. I work as part of a project, and so part of the needed code are written in different languages. As it happens, Java needs to use code written in c#.
There are more than one question here, really.
1) can I create an object defined in the dll in the Java code using JNI?
2) If it absolutely needed to be could I create a GUI in Java, and can I send the window handle as argument into the dll? (when I talk about window handle I mean the thing that I would retrieve in c# on a textBox using textBox.Handle.toInt32())
3) I heard there also exist sockets. Could you please specify the big difference between them and which one is better?
Thanks a lot.
Vic_code

Answer 1

I believe that jshell was actuall referring to the COM interface.
COM stands for Common Object Model and is a popular way in Windows for applications and components to communicate. It is nearly a synonym for ActiveX.
It is easy to add a COM interface to a C# class. All you have to do is to add the COMVisible=true attrribute to the class.
You can also use the project settings to expose the entire program to COM.
Either way, you should check the box for "Register for COM Interop" under Build in project settings.
Once your C# class has a COM interface, use jacob to access its properties and methods.
Here is example code for accessing Visual Studio from a java app:
import com.jacob.activeX.ActiveXComponent;
import com.jacob.com.Variant;
import com.jacob.com.Dispatch;
public class VisualStudioApp
private ActiveXComponent m_vsApp;
public VisualStudioApp() throws VisualStudioException
string vsVer = "VisualStudio.DTE";
m_vsApp = ActiveXComponent.connectToActiveInstance(vsVer);
if (null == m_vsApp)
m_vsApp = ActiveXComponent.createNewInstance(vsVer);
if (null != m_vsApp)
if (!MainWindow().GetVisible())
MainWindow().SetVisible(true);
if (!GetUserControl())
SetUserControl(true);
// other methods and properties as needed...
}You fill in other properties and methods as methods in the java class. For instance, the MainWindow property of the VisualStudioApp looks like:
public MainWindow MainWindow()
if (null == m_vsApp)
return null;
Variant win = m_vsApp.getProperty("MainWindow");
return new MainWindow(win.getDispatch());
}and the MainWindow class (corresponding to a MainWindow class probably written in C++ for Visual Studio but who cares) looks like:
public class MainWindow
protected Dispatch m_pDisp;
public MainWindow(Dispatch pDisp) { m_pDisp = pDisp; }
@Override protected void finalize() { m_pDisp.safeRelease(); m_pDisp = null; }
public void SetFocus()
Dispatch.call(m_pDisp, "SetFocus");
// other properties and methods here...
}Edited by: mozzis on May 21, 2009 11:10 AM
Edited by: mozzis on May 21, 2009 11:14 AM