Solved

Cant write to a RandomAccessFile?

Posted on 2003-11-22
27
323 Views
Last Modified: 2010-03-31
When I click loginbutton in the applet many errors are occuring and nothing is written to the file "Customer.txt"
The code is as follows...

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
//<applet code=Login.class Width=400 Height=400>
//</applet>

public class Login extends JApplet implements ActionListener
{

      JTextField textcustname;
      JPasswordField textpassword;
      JLabel labelcustname;
      JLabel labelpassword;
      JButton loginbutton;
      public void init()
      {
            createApplet();
      }
      public void createApplet()
      {
            Container content;
            content=getContentPane();
            content.setLayout(new FlowLayout());
            labelcustname=new JLabel("Customer Login Name:");
            textcustname=new JTextField(10);
            labelpassword=new JLabel("Password:");
            textpassword=new JPasswordField(10);
            loginbutton=new JButton("Login");
            content.add(labelcustname);
            content.add(textcustname);
            content.add(labelpassword);
            content.add(textpassword);
            content.add(loginbutton);
            loginbutton.addActionListener(this);
      }
      public void actionPerformed(ActionEvent evt)
      {
            Object obj=evt.getSource();
            if(obj==loginbutton)
            {
                  String entry=textcustname.getText() +":"+new String(textpassword.getPassword());
                  try
                  {
                        RandomAccessFile logfile=new RandomAccessFile("D:\\java\\bin\\Customer.txt","rw");
                        logfile.seek(logfile.length());
                        logfile.writeBytes(entry);

                  }

                  catch(IOException e)
                  {
                        showStatus("Cannot write on to the log file"+e);
                  }
            }
      }
}

I even set the Policytool such that "Customer.txt" file has both read and write privileges.So any suggestions please? Thanks.
0
Comment
Question by:gopikrish
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 13
  • 11
  • 3
27 Comments
 
LVL 86

Expert Comment

by:CEHJ
ID: 9802588
Please post errors
0
 

Author Comment

by:gopikrish
ID: 9802639
But I cant see all the errors since one cant scroll up in the DOS window.So any way to look through all the errors or can I post whichever is visible?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9802694
You'll have to get your DOS window organized. You have the following potential problems/potential problems:

1. You don't close the file
2. You don't check for presence of both username and password
3. Your policy file may not have been altered properly
0
Get 15 Days FREE Full-Featured Trial

Benefit from a mission critical IT monitoring with Monitis Premium or get it FREE for your entry level monitoring needs.
-Over 200,000 users
-More than 300,000 websites monitored
-Used in 197 countries
-Recommended by 98% of users

 

Author Comment

by:gopikrish
ID: 9802740
       at java.awt.Component.processMouseEvent(Component.java:5100)
        at java.awt.Component.processEvent(Component.java:4897)
        at java.awt.Container.processEvent(Container.java:1569)
        at java.awt.Component.dispatchEventImpl(Component.java:3615)
        at java.awt.Container.dispatchEventImpl(Container.java:1627)
        at java.awt.Component.dispatchEvent(Component.java:3477)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)

        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
        at java.awt.Container.dispatchEventImpl(Container.java:1613)
        at java.awt.Component.dispatchEvent(Component.java:3477)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)

        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)

        at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

These are the ones I am able to see.
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9802749
That's of no use unfortunately - it simply tells you that the problem's occurring in the event handler - which is pretty obvious anyway. You need to get your window organized and post the whole stack trace. I have no difficulty scrolling my DOS window - set its properties by right-clicking the title bar. Use the onboard help if you have difficulty
0
 

Author Comment

by:gopikrish
ID: 9803035
Hmm i tried a lot but in vain :(  I'am using win98 so maybe its not possible to view in it i guess :(
Anyway I asked about it in "Platforms/Win progs" section so lets see if anyone replies.
0
 

Author Comment

by:gopikrish
ID: 9803069
But when I open Policytool.exe it says Error Could not find policy File C:\WINDOWS\.java.policy
But my policy file is in D:\java\bin
But another program didnt had any problems in displaying a .gif image in applet.I mean same error occured but I granted Read and Execute to all files and I was able to display that image.
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9803136
Writing is quite different - go through the process again carefully - that is where your problem lies
0
 

Author Comment

by:gopikrish
ID: 9803427
Hmm but Can you try my above code and check if you are getting any errors in it or able to successfully write to a file? So that if there are no errors in that code then maybe Policyfile settings should be wrong.And what did you meant by carefully go through the process.I mean which process?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9803440
The only errors I get are security ones, although, as I mentioned before, you don't close your file, so even if there were no security errors, it wouldn't write to the file. Close it in a finally block.

>>I mean which process?

The process of doing the security settings
0
 

Author Comment

by:gopikrish
ID: 9803506
Sorry how to close a file?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9803530
              RandomAccessFile logfile = null;
               try
               {
                    logfile = new RandomAccessFile("D:\\java\\bin\\Customer.txt","rw");
                    logfile.seek(logfile.length());
                    logfile.writeBytes(entry);

               }

               catch(IOException e)
               {
                    showStatus("Cannot write on to the log file"+e);
               }
               finally
               {
                         try { logfile.close(); } catch(IOException e) { /* ignore */ }
               }
0
 

Author Comment

by:gopikrish
ID: 9803642
I did but still same errors are occuring :(
0
 
LVL 86

Accepted Solution

by:
CEHJ earned 50 total points
ID: 9803703
Save the following into the same directory as the applet as

.java.policy

and then start the appletviewer with:

appletviewer -J-Djava.security.policy=./.java.policy Login.java

grant codeBase "file:/C:/java/dumpit/-"
{
      permission java.io.FilePermission "customer.txt", "read";
      permission java.io.FilePermission "customer.txt", "write";
};      
   

Obviously, you're going to have to change the urls appropriately. You shouldn't have data/code in your Java bin directory btw
0
 

Author Comment

by:gopikrish
ID: 9803798
So I have my Login.java in the directory "D:\java\bin"
So is the following code correct for .java.policy file?
 
grant codeBase "file:/D:/java/bin/-"
{
     permission java.io.FilePermission "customer.txt", "read";
     permission java.io.FilePermission "customer.txt", "write";
};    

And what do you mean by "You shouldn't have data/code in your Java bin " ?
   


0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9803824
>>And what do you mean by "You shouldn't have data/code in your Java bin " ?

You shouldn't put data and code in there.

The code is right if customer.txt is in the same directory
0
 

Author Comment

by:gopikrish
ID: 9805063
Well I also tried with "Customer.txt" in the directory
C:\Program Files\Java\j2re1.4.2_01\bin
and creating .java.policy file in "D:\java\bin" as follows
 grant codeBase "file:/C:/Program Files/java/j2re1.4.2_01/bin/-"
{
     permission java.io.FilePermission "customer.txt", "read";
     permission java.io.FilePermission "customer.txt", "write";
};    
  Then started appletviewer from "D:\java\bin" as follows
 appletviewer -J-Djava.security.policy=./.java.policy Login.java
But still the same problem.


0
 
LVL 92

Expert Comment

by:objects
ID: 9805206
Change your catch so you can see the error:

               catch(Exception e)
               {
                    showStatus("Cannot write on to the log file"+e);
               }
0
 

Author Comment

by:gopikrish
ID: 9805691
Yes in the status bar of the applet the following error is being displayed--
Cannot write on to the log filejava.security.AccessControlException: access denied (java.io.FilePermission D:\Java\bin\Customer.txt write)
 So what to do?
0
 
LVL 92

Expert Comment

by:objects
ID: 9807020
try:

grant codeBase "file:/D:/java/bin/-"
{
     permission java.io.FilePermission "Customer.txt", "read";
     permission java.io.FilePermission "Customer.txt", "write";
};    
0
 

Author Comment

by:gopikrish
ID: 9809515
Ah Thanks now I'am able to.Actually the problem was I did "customer.txt" instead of "Customer.txt" in that grant codeBase as CEHJ did above :) Thanks objects also.
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9810004
>>Actually the problem was I did "customer.txt" instead of "Customer.txt" in that grant codeBase as CEHJ did above

It doesn't actually make any difference on Windows (certainly on Win2K)
0
 

Author Comment

by:gopikrish
ID: 9811916
Yes it CEHJ ! That was the problem actually.When I changed that it started working :)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9812380
Worked for me either way. Maybe the file had been cached in some way
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9812429
Just checked. My file is called customer.txt

      permission java.io.FilePermission "Customer.txt", "read";
      permission java.io.FilePermission "Customer.txt", "write";


and

      permission java.io.FilePermission "customer.txt", "read";
      permission java.io.FilePermission "customer.txt", "write";

work equally well.
0
 

Author Comment

by:gopikrish
ID: 9812825
ok :)
0
 
LVL 92

Expert Comment

by:objects
ID: 9814183
> Actually the problem was I did "customer.txt" instead of "Customer.txt"

No the problemn was with the specification of directory.
0

Featured Post

PeopleSoft Has Never Been Easier

PeopleSoft Adoption Made Smooth & Simple!

On-The-Job Training Is made Intuitive & Easy With WalkMe's On-Screen Guidance Tool.  Claim Your Free WalkMe Account Now

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

After being asked a question last year, I went into one of my moods where I did some research and code just for the fun and learning of it all.  Subsequently, from this journey, I put together this article on "Range Searching Using Visual Basic.NET …
Java had always been an easily readable and understandable language.  Some relatively recent changes in the language seem to be changing this pretty fast, and anyone that had not seen any Java code for the last 5 years will possibly have issues unde…
Viewers learn about the “while” loop and how to utilize it correctly in Java. Additionally, viewers begin exploring how to include conditional statements within a while loop and avoid an endless loop. Define While Loop: Basic Example: Explanatio…
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.
Suggested Courses

628 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question