How to make applet access a local file in intranet?

Question

I want to have my applet read from and write to a file on the user's PC. This is our company's intranet and security is not a concern so we don't want to go through the complicated certificate procedure.
Our application server is weblogic. The jsp containing the applet can be accessed at http://10.150.20.100:7001/slfweb/jsp/Home.jsp. According to Core Java (Volume II), I put the following paragragh into java.policy file under jre/1.3.1/lib/security dir of each user's PC, hoping this will grant the permission for the applet to read/write a file in tmp dir:
grant codeBase "10.150.20.100:7001/slfpweb/" {
permission java.io.FilePermission "C:\\tmp\\*", "read, write";
However, it does not work. Can someone tell me what is the simplest way to allow an applet to read/write a local file in intranet system?
Thank you very much!
Ming

Answer 1

I guess the reason you're still running into permission problem is that you have not addressed the required settings in the browser(s) that you're using.
On everyone's PC, the following must be done:
1) on IE, click Tools | Internet Options | Security . Under Trusted Sites, add your server's IP address. Under Local Intranet, reset it to Medium or Low and check to see if any of the relavant settings require attention (note that a Java Applet is equivalent to an ActiveX object in IE) . Finally, go into Java Custom Settings and make the appropriate changes.
2) on NN, to access local files, you can enable Codebase Principals by adding the following line to the user's pref.js file (look for it where NN is installed -- usually under C:\Program Files):
user_pref("signed.applets.codebase_principal_support", true);
I have also read Core Java and found that the authors have a way of over-simplifying everything and failure to adequately describe other factors that may potentially affect what they're describing.
V.V.
PS: Signing an applet with a self-signed certificate is not all that difficult. Here is a link to my file i/o applet that contains pertinent info that you might want to look into:
http://home.attbi.com/~aokabc/FileIO/FileIOdemo.htm