/*
* @(#)randomFile.java 1.8 10/03/24
*
* Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* -Redistribution of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of Oracle or the names of contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
* AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
* EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed, licensed or intended
* for use in the design, construction, operation or maintenance of any
* nuclear facility.
*/
/*
* This program uses JNLP API to write to a file
* that is selected by the user. We then read
* whatever is written in the file and display
* it in the text area.
*/
/*
* Please note that this application sleeps for 2 seconds
* everytime some text is added to the text area.
* This is done purely for demonstration purpose.
*/
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.lang.*;
import java.applet.*;
import javax.swing.*;
import javax.jnlp.*;
public class randomFile
{
FileOpenService fos;
JNLPRandomAccessFile raf;
FileContents fc;
static int count=0;
JTextArea textArea;
java.awt.Container contentPane;
JFrame t;
public randomFile()
{
t = new JFrame("JNLPRandomAccessFile API demo");
contentPane = t.getContentPane();
contentPane.setLayout( new FlowLayout() );
contentPane.setBackground(Color.white);
textArea = new JTextArea();
contentPane.add(textArea);
textArea.setText("Demonstrating usage of random access file. \n");
textArea.append("It behaves like a large array of bytes stored in the file system \n");
textArea.append("Pick a file to open on the local system \n");
t.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e)
{
destroy();
t.setVisible(false);
System.exit(0);
}
});
t.pack();
t.setSize(500,400);
t.setVisible(true);
// Look up a FileOpenService
try {
fos = (FileOpenService)ServiceManager.lookup("javax.jnlp.FileOpenService");
} catch (UnavailableServiceException e) {
fos = null;
}
if (fos != null) {
try {
// get a file with FileOpenService
fc = fos.openFileDialog(null, null);
// If valid file contents
if (fc != null) {
long grantedLength = fc.getLength();
if (grantedLength + 1024 > fc.getMaxLength()) {
// attempt to increase the maximum file size defined by
// the client
grantedLength = fc.setMaxLength(grantedLength + 1024);
}
// Open the file for read write
raf = fc.getRandomAccessFile("rw");
textArea.append("File selected : ");
textArea.append(fc.getName());
textArea.append("\n");
textArea.append("Created a random access file in read/write mode.... \n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void write()
{
String msg="JAVA WEB START CAN STUN YOU.. ";
if (fos != null && fc != null) {
try {
textArea.append("Seek to the begining of the file for write... \n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
// seek to the beginning and write
raf.seek(0);
/* This message will be written at the begining
** of the file. It will overwrite if it is already
** existing.
*/
textArea.append("Writing a string to the file using UTF-8 encoding... \n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
raf.writeUTF("CONGRATS !!. WRITE & READ PERFORMED SUCCESSFULLY ");
raf.seek(raf.length()-1);
textArea.append("Seek to end of the file for next write... \n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
/*
** This message will always be written at the end of
** file. It will be written once for every write you
** make to the file indicating number of times this
** message was written to the same file.
*/
textArea.append("Writing another string as a sequence of bytes \n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
raf.writeBytes("\n" + msg + count++);
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void destroy() {
if (fos != null && fc != null) {
try {
// close the file
raf.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void read()
{
if (fos != null && fc != null) {
try
{
textArea.append("Now reading whatever was written.. \n");
textArea.append("Reading one line at a time from the begining of the File.. \n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
/*
** Starting from the begining, it will read one line
** at a time from the file and append it with newline
** character.
*/
textArea.append("\n");
raf.seek(0);
String line = raf.readUTF();
while (line != null)
{
textArea.append(line);
textArea.append("\n");
line = raf.readLine();
}
textArea.append("\n");
try
{
Thread.sleep(2000);
} catch (InterruptedException e){
// the VM doesn't want us to sleep anymore,
// so get back to work
}
textArea.append("Thanks for choosing Java Web Start.. \n");
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static void main(String args[])
{
randomFile randomfile = new randomFile();
randomfile.write();
randomfile.read();
}
}