Re: [jna-users] How to access logonuser from advapi32.dll – Nikolas Lotz – net.java.dev.jna.users – MarkMail
import com.sun.jna.Library;
import com.sun.jna.ptr.IntByReference;
import com.sun.jna.win32.StdCallLibrary;
import com.sun.jna.Native;
import com.sun.jna.Platform;

public interface CLibrary extends Library {

CLibrary INSTANCE = (CLibrary) Native.loadLibrary((Platform.isWindows() ? “advapi32″ : “c"), CLibrary.class);

public boolean LogonUserA(String userName, String domain, String password, int dwLogonType, int dwLogonProvider, IntByReference lToken);
}

public static void main(String[] args) {

try {
IntByReference lToken = new IntByReference(0);

System.out.println(CLibrary.INSTANCE.LogonUserA(“username", “.", “password", 3, 0, lToken));
System.out.println(lToken);
} catch (Exception e) {
e.printStackTrace();
}

}

How use JNA, a demonstration

JNA

Java Native Access is an extension to Java that allows the use of native APIs by including dynamically library files, DLLs under Windows.

JNA is a simpler alternative to JNI which does not require to generate code for using C functions. To use them, simply include the file that defines them and declare the header of these functions in an interface.
Demonstration

To use the puts function of the C language, which is provided by the msvcrt.dll file in Windows, create the following interface:

package CInterface;

import com.sun.jna.Library;

public interface CInterface extends Library
{
public int puts(String str);
}

We have declared the CInterface interface which is a subclass of J

Simplify Native Code Access with JNA | Java.net

Linkage: What’s in a Name?

Our first example (LockWorkStation.java) is extremely simple, and locks the workstation when it is run (same effect as pressing the Windows logo + L keys together). It uses the User32 interface shown above to create a proxy for the Windows user32 DLL. It then calls the proxy’s LockWorkStation() method — which in turn invokes the DLL’s LockWorkStation() function. The run-time mapping of the proxy method to the DLL function is handled transparently by JNA — the user just has to ensure that the method name matches the function name exactly.

import com.sun.jna.Native; // JNA infrastructure
import libs.User32; // Proxy interface for user32.dll

public class LockWorkStation {
public static void main(String[] args) {

// Create a proxy for user32.dll …
User32 user32 = (User32) Native.loadLibrary(“user32″, User32.class);

// Invoke “LockWorkStation()" via the proxy …
user32.LockWorkStation();

}
}

To compile and run this program follow the instructions at “Running the Sample Code" below.

The absence of parameters and a return value in the LockWorkStation() call eliminates the possibility of any programming errors. But there are still two things that can go wrong with code as simple as this:

*

loadLibrary() throws a java.lang.UnsatisfiedLinkError with the message “Unable to load library … The specified module could not be found." If this error occurs check the spelling of the DLL name, and verify that the DLL is in one of the searched directories (check JNA documentation).
*

A proxy method (such as LockWorkStation()) throws a java.lang.UnsatisfiedLinkError with the message “Error looking up function … The specified procedure could not be found." If this error occurs check the spelling of the function name, and verify that the “function" is not actually a macro. The Windows API DLLs contain quite a few such macros (e.g. GetMessage(), defined in Winuser.h), so read the DLL’s documentation (and the associated header files) carefully. Macro names must be translated manually.

You shouldn’t get either of these exceptions when running LockWorkStation.java. But you can simulate these errors just by changing the name of a DLL or a function and recompiling the code. JNA does, in fact, have mechanisms to allow you to use a method name (in the proxy interface) that is different from the function name (in the DLL). More information on this feature can be found in the JNA documentation.

東方和風語: [Java]Java呼叫C/C++ DLL

JNA