Java applet, problem loading native dll_问答_开发者

开发者 https://www.devze.com 2023-02-19 00:12 出处：网络

I am writing a Java applet which loads dll\'s created in unmanaged C++. I am writing some basic test to get it loading.

相关专题：applet

I am writing a Java applet which loads dll's created in unmanaged C++. I am writing some basic test to get it loading.

Here's the code:

The DLL:

#define DllExport _declspec(dllexport)
DllExport int calc();


DllExport int calc() {
return 1000;
}

The applet:

import java.applet.*;
import java.awt.*;


public class app extends Applet {

   int width, height;
   private native int calc();

   public void init() {
   try {
       System.loadLibrary("appletdll.dll");
       setBackground( Color.black );
   }
   catch(Exception e) {
       setBackground( Color.red );
           开发者_如何学Go    // for debugging, is there another way to for example print 
               // exception messages in an applet?
   }

   //width = getSize().width;
   width = calc();
   height = getSize().height;
  }

  public void paint( Graphics g ) {
     g.setColor( Color.green );
     for ( int i = 0; i < 10; ++i ) {
         g.drawLine( width, height, i * width / 10, 0 );
     }
  }
}

The HTML running the applet:

<html>
<head><title>simple page</title></head>
<body>

<applet width=400 height=400 code="app.class" archive="apptest.jar"> </applet> 

</body>
</html>

All I am getting when running in Firefox is a black 400x400 background. When running in applerviewer, I get an UnsatisfiedLinkError on calc().

The .jar is signed using this guide: http://wiki.plexinfo.net/index.php?title=How_to_sign_JAR_files

In the folder I have: app.class, apptest.jar, appletdll.dll, applet.htm,

myKeystore

I am probably doing alot wrong, I am just trying to get some basics working. I've been looking at applet+dll guides but they are mostly outdated. If there is anything that is not clear, just ask.

Thanks

First, the function should be called Java_app_calc(). Second, it should take a single argument of type "JNIEnv *". That should do it.

If you run the program "javah", it can generate your C/C++ header file for you, which will help you get the function names and signatures correct. The argument is the name of a class (it operates on compiled class files:

javah app