Calling the Win32 API from Java | J/Invoke

Calling the Win32 API from Java

To make calling the Win32 API easier, the com.jinvoke.win32 package provides helper classes that contain J/Invoke declaration of functions for the most commonly used Win32 DLLs. You just need to import the class you need and directly call the stubbed out Java method corresponding to the Win32 API you want to call.

The available APIs are declared in a set of classes, one for each Windows DLL, as shown in the following table.

J/Invoke Win32 Helper Class	DLL Name	Functionality
com.jinvoke.win32.Kernel32	KERNEL32.DLL	Base services
com.jinvoke.win32.Gdi32	GDI32.DLL	Graphics device interface
com.jinvoke.win32.User32	USER32.DLL	User interface
com.jinvoke.win32.Advapi32	ADVAPI32.DLL	Crypto API, event logging
com.jinvoke.win32.Shell32	SHELL32.DLL	Windows shell API
com.jinvoke.win32.Winmm	WINMM.DLL	Multimedia
com.jinvoke.win32.WinInet	WININET.DLL	Internet

The Win32 API uses many constants and structures which are defined in com.jinvoke.win32.WinConstants class and the com.jinvoke.win32.structs package respectively.

For instance, MessageBox is contained in USER32 .DLL and therefore declared in the User32 class. Import this class and you can call MessageBox directly. Thus, the previous example could be simplified as shown below:

import com.jinvoke.win32.User32;
import static com.jinvoke.win32.WinConstants.*;

public class CallingWin32API {
    public static void main(String[] args) {
        User32.MessageBox(0, "This MessageBox is a native Win32 MessageBox", "Caption", MB_ICONINFORMATION|MB_OK);
    }
}