Applets and Writing Files

Question

mitch9654 3 Light Poster

14 Years Ago

Hello, I am having trouble writing to a file from an applet (in a local directory) without totally demolishing the file and erasing it's contents (okay, maybe I am exaggerating on the destroying part :P, but it does erase it!). Also, I just can't make the applet write to the file!

Thanks;
Mitch

java

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Latest Post 14 Years Ago Latest Post by mitch9654

NormR1 563 Posting Sage

14 Years Ago

Can you post the code?
There are two modes of writing to a file: replace or append to it.

NormR1 563 Posting Sage

14 Years Ago

The code appears to do more than write a file. Can you make A simpler test program that ONLY writes a file and would be easier to debug. Once you get the technique then you can copy the working code into your program.

The only write statement I see in your code, writes an int value.

out.write(123);

Edited 14 Years Ago by NormR1 because: n/a

NormR1 563 Posting Sage

14 Years Ago

empty means 0 bytes!

Did the out.write(123) statement execute?

Can you make A simpler test program that ONLY writes a file and would be easier to debug.

NormR1 563 Posting Sage

14 Years Ago

If the OP was having a security problem there would be error messages on the Java Console.

NormR1 563 Posting Sage

14 Years Ago

Can you make A simpler test program that ONLY writes a file and would be easier to debug.

Edited 14 Years Ago by NormR1 because: n/a

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mitch9654 3 Light Poster · Answer 1 · 2010-06-12T09:26:54+00:00

Can you post the code?
There are two modes of writing to a file: replace or append to it.

This is what I have, but it is but one file of 4 packages

package Root.Panels;

import Root.Main.Main;
import java.awt.*;
import java.io.*;
import Root.Buttons.SubButton;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URL;

/**
 *
 * @author Mitch
 */
public class AddPanel extends Panel{

    BufferedWriter bf;
    OutputStreamWriter out;
    OutputStream fout;
    OutputStream bout;

    Main app;

    Image logo;
    Image checkimg;

    String textfile;

    int inx;
    int iny;
    int width;
    int height;

    TextField songfield;
    TextField artistfield;

    SubButton submit;

    submitHandler sublistener;

    public AddPanel(Image logotemp, int inxtemp, int inytemp, int widthtemp,
            int heighttemp, URL filetemp, Image checkimgtemp, Main apptemp) {
        super();
        logo = logotemp;
        checkimg = checkimgtemp;
        app = apptemp;

        inx = inxtemp;
        iny = inytemp;
        width = widthtemp;
        height = heighttemp;

        textfile = filetemp.toString();
        textfile = textfile.replace("index.html", "songs.DAT");
        textfile = textfile.replace("Main.html", "songs.DAT");

        if(textfile.equals(filetemp.toString()))
        textfile += "songs.DAT";

        textfile = textfile.replace("file:", " ");

        textfile = textfile.trim();

        try {
        fout = new FileOutputStream(textfile);
        }
        catch(FileNotFoundException e) {
            e.printStackTrace();
        }
        bout = new BufferedOutputStream(fout);

        sublistener = new submitHandler();
        songfield = new TextField(30);
        artistfield = new TextField(30);
        submit = new SubButton("Submit", 0, 0, 70, 25, checkimg, this);

        songfield.setBounds(inx, iny + height + 33, width, 20);
        artistfield.setBounds(inx, iny + height + 69, width, 20);
        submit.setBounds(200 / 2 - 35, iny + height + 92, 70, 25);

        submit.addActionListener(sublistener);

        add(songfield);
        add(artistfield);
        add(submit);
    }

    @Override
    public void paint(Graphics g) {

        g.setColor(Color.GRAY);
        g.fillRect(0, 0, 200, 150);

        g.setColor(Color.WHITE);
        g.drawString("Please enter your:", inx + 40,
                iny + height + 12);
        g.drawString("Song Name", inx, iny + height + 30);
        
        g.drawString("and Artist", inx, iny + height + 66);

        g.drawImage(logo, inx, iny, width, height, this);

        super.paint(g);

    }

    private void close() {
        app.addframe.hide();
    }

    private class submitHandler implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            filehandle();
            close();
        }

    private void filehandle() {

        String song = songfield.getText();
        String artist = artistfield.getText();
        int total = app.viewpanel.connect();
        out = new OutputStreamWriter(bout);
        try {
        out.write(123);
        }
        catch (IOException e) {
            e.printStackTrace();
        }

    }

    }

}

Thanks,
Mitch

mitch9654 3 Light Poster · Answer 2 · 2010-06-12T09:59:07+00:00

The code appears to do more than write a file. Can you make A simpler test program that ONLY writes a file and would be easier to debug. Once you get the technique then you can copy the working code into your program.
The only write statement I see in your code, writes an int value.
out.write(123);

I was only writing an int value for a test... It didn't work

Could you give me an example of a working program that puts data into a file?

NormR1 563 Posting Sage Team Colleague · Answer 3 · 2010-06-12T10:27:36+00:00

How do you know it didn't work? What did the file that was written have in it?
Remember the data is int not String. So you'll need a hex editor to see it. And the hex value for 123.

mitch9654 3 Light Poster · Answer 4 · 2010-06-12T10:50:27+00:00

How do you know it didn't work? What did the file that was written have in it?
Remember the data is int not String. So you'll need a hex editor to see it. And the hex value for 123.

the file was empty. It used to have 4 lines of data

aspire1 36 Light Poster · Answer 5 · 2010-06-12T15:18:32+00:00

As far as I'm aware applets can't by default write to the local file system: security. Google should show you how to do it.

mitch9654 3 Light Poster · Answer 6 · 2010-06-12T20:53:42+00:00

empty means 0 bytes!
Did the out.write(123) statement execute?

Oh yeah, it was 100% empty. 0 bytes for the file size

But The out.write(123) statement did execute

Also, I am running the whole thing under appletviewer, which always allows me to read files. (I am assuming that writing is a given to)

Thanks,
Mitch

mitch9654 3 Light Poster · Answer 7 · 2010-06-12T21:35:43+00:00

Can you make A simpler test program that ONLY writes a file and would be easier to debug.

ok, here:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package test;

import java.applet.Applet;
import java.io.*;

/**
 *
 * @author Mitch
 */
public class test extends Applet{

    OutputStreamWriter out;
    OutputStream fout;
    OutputStream bout;

    @Override
    public void init() {

        try {
        fout = new FileOutputStream("E:/Documents and Settings/Mitch/My Documents/NetBeansProjects/DanceProject/build/songs.txt");
        System.out.println("1");
        }
        catch(FileNotFoundException e) {
            e.printStackTrace();
        }
        bout = new BufferedOutputStream(fout);
        out = new OutputStreamWriter(bout);
        System.out.println("2");
        try {
        out.write("hi");
        System.out.println("3");
    }
    catch(IOException e) {
        e.printStackTrace();
    }

}
}

The numbers that came up on the bottom (from System.out.println();) was:

1
2
3

Hope that helps

Thanks, Mitch

NormR1 563 Posting Sage Team Colleague · Answer 8 · 2010-06-12T23:06:20+00:00

I get security errors when I run your code.

When executed via an HTML in a browser, I get following in Java Console:
java.security.AccessControlException: access denied (java.io.FilePermission TestWriteApplet_Output.txt write)
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkWrite(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at TestWriteApplet.init(TestWriteApplet.java:23)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.security.AccessControlException: access denied (java.io.FilePermission TestWriteApplet_Output.txt write)
Executing using AppletViewer:
Running: D:\Java\jdk1.6.0_02\bin\appletviewer.exe TestWriteApplet.java
java.security.AccessControlException: access denied (java.io.FilePermission TestWriteApplet_Output.txt write)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkWrite(SecurityManager.java:962)
at java.io.FileOutputStream.<init>(FileOutputStream.java:169)
at java.io.FileOutputStream.<init>(FileOutputStream.java:70)
at TestWriteApplet.init(TestWriteApplet.java:23)
at sun.applet.AppletPanel.run(AppletPanel.java:418)
at java.lang.Thread.run(Thread.java:619)

mitch9654 3 Light Poster · Answer 9 · 2010-06-13T02:42:42+00:00

Could you give me an example of a working file writing applet?

Thanks,
Mitch

NormR1 563 Posting Sage Team Colleague · Answer 10 · 2010-06-13T02:55:30+00:00

NormR1 563 Posting Sage

14 Years Ago

Yes and NO. I have applets that are loaded from local files and can write on local disks. However they require permission to do that. I give them permission by putting an entry in the .java.policy file:

grant codeBase "file:/D:/JavaDevelopment/Testing/WriteFile/-" {
  permission java.io.FilePermission "D:/Testing/*", "read, write";    /* Allow write of file to this directory */
};

The code is in: D:/JavaDevelopment/Testing/WriteFile
and the above allows it to write to the folder: D:/Testing/

This program is at least 9 years old acording to the date on a jar file in the test folder. I copied it from some text book.

WriteFile.java (2.62 KB)

/**
  * By default, this applet raises a security exception, unless
  *  you configure your policy to allow applets from its location
  *  to write to the file "writetest".

  <applet code=WriteFile.class width=700 height=150>
  </applet>  
*/

import java.awt.*;
import java.io.*;
//import java.lang.*;
import java.applet.*;
import java.util.Date;
import java.security.*;

public class WriteFile extends Applet {
    String myFile = "D:\\Testing\\writetest.txt";    // The file to write
    File f = new File(myFile);
    DataOutputStream dos;

    String message = "";

  public void init() {
    String osname = System.getProperty("os.name");
    System.out.println("os.name is " + osname);
    System.out.println("Java version is " + System.getProperty("java.version"));
    // Following added for tests with IE7 - Still does not allow wildcards in .java.policy file
/*
grant codeBase "file:/D:/JavaDevelopment/Testing/WriteFile/-" {
/*  permission java.io.FilePermission "D:/Testing/writetest.txt", "read, write";  IE7 works*/ /*
  permission java.io.FilePermission "D:/Testing/*", "read, write";   // IE7 fails
};
*/
    AccessController.doPrivileged(new PrivilegedAction() {
        public Object run() {
            System.out.println("Starting PrivilegedAction");
         	try {
           	  dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(myFile),128));
         	  dos.writeBytes("Cats can hypnotize you when you least expect it\n" + new Date() + "\n");
         	  dos.flush();
              dos.close();
         	  message = "Successfully wrote to the file named " + myFile 
                                  + " -- go take a look at it!";
         	}
         	catch (SecurityException e) {
         	  message = "writeFile: ex: " + e;
              e.printStackTrace();
            }
         	catch (IOException ioe) {
         		message = "writeFile: caught i/o exception " + ioe;
              ioe.printStackTrace();
            }
            repaint();              // go show message
            return null;
        }
    });
  } // end init()

 public void paint(Graphics g) {
   g.drawString(message, 10, 10); // show the message
/*
	try {
  	  dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(myFile),128));
	  dos.writeBytes("Cats can hypnotize you when you least expect it\n" + new Date() + "\n");
	  dos.flush();
	  g.drawString("Successfully wrote to the file named " + myFile + " -- go take a look at it!", 10, 10);
	}
	catch (SecurityException e) {
	  g.drawString("writeFile: ex: " + e, 10, 10);
   }
	catch (IOException ioe) {
		g.drawString("writeFile: caught i/o exception", 10, 10);
   }
*/
 }
}

mitch9654 3 Light Poster · Answer 11 · 2010-06-13T02:58:20+00:00

I use jarsigner, which I do after.

I just tried the jarsigner and it still wouldn't work (but no errors! Yes!)

I don't get why it won't write to the file!

I just changed my slashes from / to \\, (oops! I forgot that one!)

Thanks,
Mitch

NormR1 563 Posting Sage Team Colleague · Answer 12 · 2010-06-13T03:07:13+00:00

I can't understand how your code wrote the println() output: 1 2 3 but didn't write any data to the file. Your code must have permission. ???
Do you close() the file after writing to it?

mitch9654 3 Light Poster · Answer 13 · 2010-06-13T03:08:54+00:00

Aha!!!!!

the close() statement!!!!

Sweet! thanks!!!!

Thanks,
Mitch