Referencing DLL in JApplet

Question

i have native elements i wish to include in one of my JApplets
I've tested the DLL using a command line style program, and it connects fine. Hence I am confident the DLL itself was built properly.
However, when i use an init() method instead of a main() (start with appletviewer instead of java.exe), it gives an access denied message. Are applets 'not allowed' to open DLLs. If not, there must be some sort of security setting that I have overseen
i use this code in the JApplet subclass, outside other methods
static {
try {
System.loadLibrary("MyWindow");
} catch (Exception e) {
JOptionPane.showMessageDialog(frame, e.getMessage());
}any help loading native elements in JApplet would be appreciated
mike

Answer 1

Mike,
Chris is correct. You will have to sign the applet. What's more...you are correct you will have to copy the dll to the users filesystem. I have been working on this for a couple weeks and here are my findings.
Project:
Create an applet that can access the clients com ports.
Requiremnents:
Comm port access requires the win32com.dll, the comm.jar api code and the javax.comm.properties files.
Findings:
The ONLY way for native library access(i.e to the dll) is for that DLL to reside on the clients local drive. I tried everything and did a ton of research...I even despeartely tried to change the java.lang.Classloader (which was of course forbidden). There's a private vector in Classloader that stores the native libraries and the only way to get added to that vector is to be one the local hard drive.
What this means:
You either need the client to already have the dll installed or you need your applet to write it to their filesystem. Also if you are using the loadLibrary method instead of the load method you must make sure the dll is written to a location that is in the user's path.
The ONLY way to write a file to the clients machine is to have file write permission. To do this your applet will have to be signed. It may not be elegant but that's all you've got.(Or you can ask the user to edit their java.policy file...ha!). Signing really isn't that big of a deal...scary would be allowing you to access the DLL without signing your code....yikes!
Conclusion:
Once you have written the dll to the users local system (in my case the win32com.dll) my signed applet along with the signed version of the comm.jar are able to open and communicate with the com ports. If you would like some code snippets or more detail on my implementation I'd be happy to post them
P.S. Anyone implementatingthe java.comm example specifically will also have to copy the javax.comm.properties file to the users drive. Otherwise the driver intializer will return name cannot be null ...you could probably fix this if you modified the comm package slightly but it's a bit of a blackbox since sun isn't giving away the source code