Cannot access file from JApplet

Question

I have used the swingall.jar file with my JApplet for any
version of IE. It gives one error
i.e
Cannot access file c:\prog\project
I want to create a directory within c:\prog and also i want
to write some files there. Pls help me.

Answer 1

try this my friend!
1.     Compile the applet
2.     Create a JAR file
3.     Generate Keys
4.     Sign the JAR file
5.     Export the Public Key Certificate
6.     Import the Certificate as a Trusted Certificate
7.     Create the policy file
8.     Run the applet
Susan
Susan bundles the applet executable in a JAR file, signs the JAR file, and exports the public key certificate.
1.     Compile the Applet
In her working directory, Susan uses the javac command to compile the SignedAppletDemo.java class. The output from the javac command is the SignedAppletDemo.class.
javac SignedAppletDemo.java
2.     Make a JAR File
Susan then makes the compiled SignedAppletDemo.class file into a JAR file. The -cvf option to the jar command creates a new archive (c), using verbose mode (v), and specifies the archive file name (f). The archive file name is SignedApplet.jar.
jar cvf SignedApplet.jar SignedAppletDemo.class
3.     Generate Keys
Susan creates a keystore database named susanstore that has an entry for a newly generated public and private key pair with the public key in a certificate. A JAR file is signed with the private key of the creator of the JAR file and the signature is verified by the recipient of the JAR file with the public key in the pair. The certificate is a statement from the owner of the private key that the public key in the pair has a particular value so the person using the public key can be assured the public key is authentic. Public and private keys must already exist in the keystore database before jarsigner can be used to sign or verify the signature on a JAR file.
In her working directory, Susan creates a keystore database and generates the keys:
keytool -genkey -alias signFiles -keystore susanstore -keypass kpi135 -dname "cn=jones" -storepass ab987c
This keytool -genkey command invocation generates a key pair that is identified by the alias signFiles. Subsequent keytool command invocations use this alias and the key password (-keypass kpi135) to access the private key in the generated pair.
The generated key pair is stored in a keystore database called susanstore (-keystore susanstore) in the current directory, and accessed with the susanstore password (-storepass ab987c).
The -dname "cn=jones" option specifies an X.500 Distinguished Name with a commonName (cn) value. X.500 Distinguished Names identify entities for X.509 certificates.
You can view all keytool options and parameters by typing:
keytool -help
4.     Sign the JAR File
JAR Signer is a command line tool for signing and verifying the signature on JAR files. In her working directory, Susan uses jarsigner to make a signed copy of the SignedApplet.jar file.
jarsigner -keystore susanstore -storepass ab987c -keypass kpi135 -signedjar SSignedApplet.jar SignedApplet.jar signFiles
The -storepass ab987c and -keystore susanstore options specify the keystore database and password where the private key for signing the JAR file is stored. The -keypass kpi135 option is the password to the private key, SSignedApplet.jar is the name of the signed JAR file, and signFiles is the alias to the private key. jarsigner extracts the certificate from the keystore whose entry is signFiles and attaches it to the generated signature of the signed JAR file.
5.     Export the Public Key Certificate
The public key certificate is sent with the JAR file to the whoever is going to use the applet. That person uses the certificate to authenticate the signature on the JAR file. To send a certificate, you have to first export it.
The -storepass ab987c and -keystore susanstore options specify the keystore database and password where the private key for signing the JAR file is stored. The -keypass kpi135 option is the password to the private key, SSignedApplet.jar is the name of the signed JAR file, and signFiles is the alias to the private key. jarsigner extracts the certificate from the keystore whose entry is signFiles and attaches it to the generated signature of the signed JAR file.
5: Export the Public Key Certificate
The public key certificate is sent with the JAR file to the whoever is going to use the applet. That person uses the certificate to authenticate the signature on the JAR file. To send a certificate, you have to first export it.
In her working directory, Susan uses keytool to copy the certificate from susanstore to a file named SusanJones.cer as follows:
keytool -export -keystore susanstore -storepass ab987c -alias signFiles -file SusanJones.cer
Ray
Ray receives the JAR file from Susan, imports the certificate, creates a policy file granting the applet access, and runs the applet.
6.     Import Certificate as a Trusted Certificate
Ray has received SSignedApplet.jar and SusanJones.cer from Susan. He puts them in his home directory. Ray must now create a keystore database (raystore) and import the certificate into it. Ray uses keytool in his home directory /home/ray to import the certificate:
keytool -import -alias susan -file SusanJones.cer -keystore raystore -storepass abcdefgh
7.     Create the Policy File
The policy file grants the SSignedApplet.jar file signed by the alias susan permission to create newfile (and no other file) in the user's home directory.
Ray creates the policy file in his home directory using either policytool or an ASCII editor.
keystore "/home/ray/raystore";
// A sample policy file that lets a JavaTM program
// create newfile in user's home directory
// Satya N Dodda
grant SignedBy "susan"
     permission java.security.AllPermission;
8.     Run the Applet in Applet Viewer
Applet Viewer connects to the HTML documents and resources specified in the call to appletviewer, and displays the applet in its own window. To run the example, Ray copies the signed JAR file and HTML file to /home/aURL/public_html and invokes Applet viewer from his home directory as follows:
Html code :
</body>
</html>
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="600" height="400" align="middle"
codebase="http://java.sun.com/products/plugin/1.3/jinstall-13-win32.cab#Version=1,3,1,2">
<PARAM NAME="code" VALUE="SignedAppletDemo.class">
<PARAM NAME="archive" VALUE="SSignedApplet.jar">
<PARAM NAME="type" VALUE="application/x-java-applet;version=1.3">
</OBJECT>
</body>
</html>
appletviewer -J-Djava.security.policy=Write.jp
http://aURL.com/SignedApplet.html
Note: Type everything on one line and put a space after Write.jp
The -J-Djava.security.policy=Write.jp option tells Applet Viewer to run the applet referenced in the SignedApplet.html file with the Write.jp policy file.
Note: The Policy file can be stored on a server and specified in the appletviewer invocation as a URL.
9.     Run the Applet in Browser
Download JRE 1.3 from Javasoft
save this to write.jp
keystore "/home/ray/raystore";
// A sample policy file that lets a JavaTM program
// create newfile in user's home directory
// Satya N Dodda
grant {
permission java.security.AllPermission;
save this to signedAppletDemo.java
* File: @(#)SignedAppletDemo.java     1.1
* Comment:     Signed Applet Demo
* @(#)author: Satya Dodda
* @(#)version: 1.1
* @(#)date: 98/10/01
import java.applet.Applet;
import java.awt.Graphics;
import java.io.*;
import java.awt.Color;
* A simple Signed Applet Demo
public class SignedAppletDemo extends Applet {
public String test() {
setBackground(Color.white);
     System.out.println(System.getProperty("user.home"));
     String fileName = System.getProperty("user.home") +
                    System.getProperty("file.separator") +
                    "newfile";
     String msg = "This message was written by a signed applet!!!\n";
     String s ;
     try {
     FileWriter fos = new FileWriter(fileName);
     fos.write(msg, 0, msg.length());
     fos.close();
     s = new String("Successfully created file :" + fileName);
     } catch (Exception e) {
     System.out.println("Exception e = " + e);
     e.printStackTrace();
     s = new String("Unable to create file : " + fileName);
     return s;
public void paint(Graphics g) {
g.setColor(Color.blue);
g.drawString("Signed Applet Demo", 120, 50);
g.setColor(Color.magenta);
g.drawString(test(), 50, 100);