I am trying to call a method in a DLL using JNA. So far have loaded the DLL using
Runtime.getRuntime().load("myworkspace/test.dll");
This dll contaings a method that I need to access. How can I execute the method present in DLL in my Java file. Do I create an object or something of the DLL and then get the method name after the dot operator.
From the source:
package jnahelloworldtest;
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.NativeLong;
import com.sun.jna.Platform;
import com.sun.jna.*;
/** Simple example of native library declaration and usage. */
public class Main {
public interface simpleDLL extends Library {
simpleDLL INSTANCE = (simpleDLL) Native.loadLibrary(
(Platform.isWindows() ? "simpleDLL" : "simpleDLLLinuxPort"), simpleDLL.class);
// it's possible to check the platform on which program runs, for example purposes we assume that there's a linux port of the library (it's not attached to the downloadable project)
byte giveVoidPtrGetChar(Pointer param); // char giveVoidPtrGetChar(void* param);
int giveVoidPtrGetInt(Pointer param); //int giveVoidPtrGetInt(void* param);
int giveIntGetInt(int a); // int giveIntGetInt(int a);
void simpleCall(); // void simpleCall();
}
public static void main(String[] args) {
simpleDLL sdll = simpleDLL.INSTANCE;
sdll.simpleCall(); // call of void function
int a = 3;
int result1 = sdll.giveIntGetInt(a); // calling function with int parameter&result
System.out.println("giveIntGetInt("+a+"): " + result1);
String testStr = "ToBeOrNotToBe";
Memory mTest = new Memory(testStr.length()+1); // '+1' remember about extra byte for \0 character!
mTest.setString(0, testStr);
String testReturn = mTest.getString(0); // you can see that String got properly stored in Memory object
System.out.println("String in Memory:"+testReturn);
Memory intMem = new Memory(4); // allocating space
intMem.setInt(0, 666); // setting allocated memory to an integer
Pointer intPointer = intMem.getPointer(0);
int int1 = sdll.giveVoidPtrGetInt(Pointer.NULL); // passing null, getting default result
System.out.println("giveVoidPtrGetInt(null):" + int1);
int int2 = sdll.giveVoidPtrGetInt(intMem); // passing int stored in Memory object, getting it back
//int int2 = sdll.giveVoidPtrGetInt(intPointer); causes JVM crash, use memory object directly!
System.out.println("giveVoidPtrGetInt(666):" + int2);
byte char1 = sdll.giveVoidPtrGetChar(Pointer.NULL); // passing null, getting default result
byte char2 = sdll.giveVoidPtrGetChar(mTest); // passing string stored in Memory object, getting first letter
System.out.println("giveVoidPtrGetChar(null):" + (char)char1);
System.out.println("giveVoidPtrGetChar('ToBeOrNotToBe'):" + (char)char2);
}
}