Tech Erudition

Google Chrome: input type="search" & results HTML attribute!

2012-01-27T10:58:00.000-08:00

Pulled my hair for a while as the search icon did not appear inside "input type='search'" on Chrome.

Took a while to realize that I had missed results=".." attribute (number of history item to drop-down) in the HTML tag!

<input type="search" placeholder="Search" results="3" ...>

Boilerplate template for apache ant build.xml

2012-01-20T00:13:00.000-08:00

Pulled up the basic boilerplate template for Apache ant build.xml that was written year's back.
You might find it useful to extend it further. Find it here.

Filesearch in download directory

2011-10-04T04:28:00.000-07:00

I found myself re-downloading files that was available in central-download-server (on internal LAN). The issue was primary the lack of web-enabled search application.

Developed a simple application using (PHP + jQuery + find command) that lets user to search for the files in the download server directory, if nothing found suggest for Google search.

Here is the download details.

Javascript Array Sort Custom Comparator

2011-06-28T05:50:00.001-07:00

Javascript Array.sort() allows you to define custom comparators!

var numbers = [10, 20, 5, -10, 30];

// Sorting in ascending order.
numbers.sort(function(a, b){return a-b;});

// Sorting in descending order
numbers.sort(function(a, b){return b-a;});

i18n-translator: makes it easy to translate and verify

2011-06-14T05:03:00.000-07:00

Translating strings using online-services for providing internalization support might be a fun job. However, you could end up with inconsistent translation. Verifying the translation across different services would helpful. i18n-translator could be handy tool for it.

PHP Performance Tuning: Watch out for notices, warnings, errors...

2011-06-01T13:51:00.000-07:00

PHP error reporting like notices, warnings... adds performance overhead and would make it hard to trace. During development make sure to turn-on error_reporting (E_ALL) and fix the issues logged, it helps your code to reach production quality.

Android 3.0 (Gingerbird) - Drains Battery!!!

2011-03-10T22:39:00.000-08:00

Last week I upgraded to Gingerbird (Android 3.0) and noticed heavy battery draining! Turning off Wifi helped in retaining device run on battery for longer time :)

Working with Remote URL - BlackBerry Simulator

2011-03-04T02:20:00.001-08:00

If you are getting started to work BlackBerry development and aim at fetching connect from remote URL, to test with Blackberry simulator review the following:

* Setup Wifi on the Blackberry Simulator.

* Blackberry MDS is running - without which Remote URL fetch attempt silently fails.

* Grant access in the app (config.xml)
<access subdomains="true" uri="http://targetdomain.tld"> or
<access subdomains="true" uri="*">

* Now launch the app and test the url fetch. (assuming it uses javax.microedition.io.* classes)

NOTE: Blackberry MDS failed to work as expected on Windows Vista/Windows 7, I had to switch on Windows XP!

va_callback plugin for jQuery

2011-02-04T04:52:00.000-08:00

Passing state information through variables for callback function is essential.
Although jQuery proxy API is available, it does not seem to accept more arguments to be tunneled for the callback.

jquery-vacallback plugin targets to achieve the same.

Click to download plugin. Look at the example.

TextMate - Themes

2011-02-04T03:18:00.000-08:00

Following places could help you find themes for TextMate.

http://wiki.macromates.com/Themes/UserSubmittedThemes
https://github.com/filmgirl/TextMate-Themes
http://textmatetheme.com/themes

fileloader plugin for jquery 1.5

2011-02-01T13:34:00.000-08:00

jquery 1.5 has introduced Deferred Object feature.

fileloader plugin is developed taking advantage of the same.

This should help you to build classes, which loads the resources required ondemand and proceed with operation once the fetch is completed.

Click to download plugin. Look at the example.

Privilege - a Freedom factor

2011-01-10T01:10:00.000-08:00

One who misuses privilege,
is not worthy for freedom.

Ignorance - Courage - Wisdom

2010-12-25T09:48:00.000-08:00

Ignorance is Past,
Courage is Present,
Wisdom is Future.

gnu-hylafax: scheduler NAK'd request ?

2010-12-14T04:14:00.000-08:00

Working with gnu-hylafax library is a great, but if you don't pay careful attention it can blow your mind and keep you awake the whole night!

I kept wonder why sendfax command works fine but application built using gnu-hylafax library ends up with exception.

460 Failed to submit job *: Unspecified reason (scheduler NAK'd request).
        at gnu.hylafax.HylaFAXClientProtocol.jsubm(HylaFAXClientProtocol.java:702)
        at gnu.hylafax.HylaFAXClient.submit(HylaFAXClient.java:632)
        ...

On reason for this was missing call to job.setKillTime("value"); (preferable to set value as 00259) This translates to JPARAM LASTTIME value command.

How to trace the issue?

Enable Log4JLogger for the application, you should be able to get the trace of all the TELNET commands executed. Verify the same with (sendfax -vv ...)

Sample log4j.properties file with gnu.hylafax.ClientProtocol logger:

#set the level of the root logger to DEBUG and set its appender as an appender named X
log4j.rootLogger = DEBUG, X

log4j.logger.X = DEBUG, X
log4j.logger.gnu.hylafax.ClientProtocol = DEBUG, X

#set the appender named X to be a console appender
log4j.appender.X=org.apache.log4j.ConsoleAppender

#set the layout for appender named X to be a pattern layout 
log4j.appender.X.layout=org.apache.log4j.PatternLayout

Commons Logging - Log4J Configuration

2010-12-14T02:40:00.001-08:00

If you use commons-logging in your java application, make sure to have log4j library (jar) and log4j.properties file on the class path. You really don't need much tweaking to get started :)

Simple log4j.properties file:

# Set root logger level to DEBUG and its only appender to A1.
log4j.rootLogger=DEBUG, A1

# A1 is set to be a ConsoleAppender.
log4j.appender.A1=org.apache.log4j.ConsoleAppender

# A1 uses PatternLayout.
log4j.appender.A1.layout=org.apache.log4j.PatternLayout

To learn more on jump to log4j manual

Boilerplate app for PHP

2010-10-21T10:57:00.000-07:00

Getting a quick start on application development adds a lot to subsequent progress.

Boilerplate app for PHP is once such attempt where the skeleton structure is ready to give you the quick start. The application is developed using the MVC architecture. It is integrated with Smarty, MDB2 libraries.

You will need to update config.php with database details and
start adding the logic to install.php, index.php, administrator.php

Repository location: http://boilerplate-apps.googlecode.com/svn/trunk/php

Get a copy to start: svn export http://boilerplate-apps.googlecode.com/svn/trunk/php boilerplate-php

Hope you will find it useful.

What makes a team poor?

2010-09-17T21:39:00.000-07:00

Having right ones at wrong place,
and Wrong ones at right place!

GWT on Netbeans?

2010-09-15T03:15:00.000-07:00

Follow the post: Create a GWT Application from Scratch to get started with GWT on Netbeans!

If try to install GlassFish server and end up with reference problems to library (javaee-endorse-api) try installing 'EJB and EAR' plugin as pointed out at
Missing "javaee-endorsed-api-6.0" Class Library it should help.

Programmer's Notepad - pnotepad

2010-01-28T00:09:00.000-08:00

If you are looking around for a light-memory footprint editor for quick coding with highlight and add-on support give Programmer's Notepad a try.

For coloring scheme you visit, downloads section

UPDATE: With Default Preset, 'Consolas', 10px Font configuration this editor works pretty much like TextMate. Learn about Projects, Project Groups and Magic folder for organizing your code.

Installing GNUStep on Fedora Core

2010-01-11T02:49:00.000-08:00

In the journey of installing GNUStep on my Fedora Core machine, I noted couple of useful pointers
that could help you save sometime.

* Install GNUStep Make from yum repository (yum install gnustep-make)

* make (compile source) and install GNUStep Base

You will need the following:
export GNUSTEP_MAKEFILES=/usr/lib/GNUstep/Makefiles/

* make (compile source) and install GNUStep GUI

You need to update ldconfig.

vim /etc/ld.so.conf.d/gnustep.conf

Add the content below and save:
/usr/local/lib/ix86/linux-gnu/gnu-gnu-gnu

Execute:
/sbin/ldconfig

* make (compile source) and install GNUstep Backend

You will need the following:
export PATH=$PATH:/usr/local/bin/ix86/linux-gnu/gnu-gnu-gnu

Check out complete documentation on steps followed at How to install GNUStep on Fedora Core

serialize/unserialize php API - an observation

2010-01-01T23:24:00.000-08:00

On first request, I was saving the object into session.

$userInstance = new Users_Model();
$_SESSION['__key'] = $userInstance;

Make sure the class Users_Model definition is available.

On second request, I retrieve the object from session for re-use.

$retrievedUserInstance = $_SESSION['__key'];

object(__PHP_Incomplete_Class)[1]
  public '__PHP_Incomplete_Class_Name' => string 'Users_Model' (length=11)
    private 'id' => string '1' (length=1)
    // ...

I noticed the $retrieveUserInstance object missed several methods!!

I realized that on second request, the class Users_Model definition
is not available on the page load and unserialize API is not working as expected.

$_SESSION values are saved using serialize API (as session.save_handler was set to files)

On making the class definition available before session_start() call,
the $retrieveUserInstance worked fine.

object(Users_Model)[1]
  private 'id' => string '1' (length=1)
  // ...

Hope it saves sometime for you.

pedit - simple text editor

2009-12-20T02:54:00.000-08:00

I'm happy to make available to source-code of my memorable text editor (pedit)
that was developed as part of my Graduation (semester) project.

pedit is written using ncurses library and C++ language, with Object Oriented Programming concepts.

Give a try and feel free to extend it. If you have any feedback do keep me posted.

Prototypejs 1.6 clash with JSON !!

2009-11-12T06:52:00.000-08:00

Prototypejs 1.6 could break your JSON API usage, be careful !

This article could be a time-saver, prototype.js breaks Firefox 3.5 native JSON

Prototype - Event.fire exception to be handled for IE

2009-11-02T02:22:00.000-08:00

Prototype 1.6 has introduced Event.fire API that works pretty well in Firefox but experienced a problem in IE (7).

Exception was being thrown in Event.fire API that needed a special treat.

The highlighted workaround worked for me:

fire: function(element, eventName, memo) {
    // ...
    if (document.createEvent) {
        element.dispatchEvent(event);
    } else {
        try{
        element.fireEvent(event.eventType, event);
        } catch(error) {
        // Error: No such interface supported (IE)
           element.fireEvent(event.eventType);
        }
    }
    return event;
}

Example:

Event.fire('myhidden_element_id', 'custom:change');

mysql-java-connector: ResultSet getObject failure on Timestamp column if null

2009-10-31T08:34:00.000-07:00

I had strange situation working with ResultSet when fetching Timestamp column from MyTable.

import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

Class.forname("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection(
"jdbc:mysql://host:port/database", 
"username", "password");

Statement statement = connection.createStatement();
ResultSet rs = statement.executeQuery("SELECT timestamp_column FROM mytable");

while(rs.next()) {
    rs.getObject("timestamp_column");
}

The cause of the failure was due to null value in timestamp_column !

The solution suggested about (zeroDateTimeBehavior=convertToNull) in the article, helped me overcome the failure.

All you need to do is:

Connection connection = DriverManager.getConnection(
"jdbc:mysql://host:port/database?zeroDateTimeBehavior=convertToNull", 
"username", "password");

Eclipse Editor - Setting Line Delimiter Style

2009-10-28T22:46:00.001-07:00

Was going crazy with my eclipse as line delimiter was different than other editors. This was causing issue with SVN commits (mixed line delimiters!)

Finally, found the way of setting the line preferences for Eclipse.

It is located under: Windows > Preferences > General > Workspace

Lynx - Text Only Browser for Windows!

2009-09-15T11:09:00.000-07:00

Text only browser could speed up your work specially if you are on a low-speed internet connection and getting distracted with graphics on the web applications :)

Got hold of Lynx on windows, which is a cool text browser I have been using on remote servers!

Well, its easy to get started, download and configure the lynx.bat and lynx.cfg files.

PHPTAL - Template Attribute Language for PHP

2009-09-11T10:16:00.000-07:00

It was fun to work with PHPTAL and walk team with a basic introduction today :). [Download here]

Doc Comment could be a source of data!!!

2009-08-27T05:28:00.000-07:00

While discussing ways of using PHP as data storage file, we passed over this interesting possibility.

PHP data file: CommentDataClass.php

/**
Doc Comment could be a SOURCE OF DATA
This could be your data in string format!!
*/
class CommentDataClass { }

?>

Retrieving data: Data.php

include_once 'CommentDataClass.php';

// Taking advantage of PHP 5.x Reflection,
// Refer: http://in.php.net/oop5.reflection

$reflectedClass = new ReflectionClass('CommentDataClass');

if(preg_match("/\/\*\*(.*)\*\//s", 
     $reflectedClass->getDocComment(), $matches)) {
 $data = $matches[1];
 $data = trim($data);
 
 var_dump(explode("\n", $data));
}
?>

Well, this is just for fun, we don't recommend it for serious use :)

Apache 2.0 with PHP 5.3.0 on Windows

2009-07-31T03:56:00.000-07:00

It took me sometime today to get my Apache 2.0 to run with PHP 5.3.0.

The builds for windows is available at http://windows.php.net/download/

Download the VC6 x86 Build of PHP 5.3.0 build and unzip.

NOTE: VC9 x86 Build of PHP 5.3.0 build might not work with Apache 2.0 !!

You will need to make the following changes in your httpd.conf

LoadModule php5_module "c:/path_to_your/5.3.0/php5apache2.dll"
PhpIniDir "c:/path_to_your/5.3.0"
ScriptAlias /php/ "c:/path_to_your/5.3.0"

Gmail survey message - inconsistent !!!

2009-07-21T00:11:00.000-07:00

I noticed the survey message flash on my Gmail account today marked as (last chance!)

Clicked on it to participate and was disappointed to get this message...

How did inconsistent behavior creep in??

Playing with Camtasia project file

2009-07-02T05:28:00.000-07:00

I had created a video using Camtasia last night using screenshot and planned to upload in the morning.
Before turning off the system, I moved the images into another drive.

In the morning, I opened the .camproj (Camtasia project) file and to my surprise all the images in it gone missing :(

A dialog box was presented to search and point location for each image. I had almost 50+ images!

With curiosity I opened (Introduction.camproj) in text editor it was a simple XML file :)

The imported images were looking like:
<clipbin_object>
<clipname>C:\Users\power\Desktop\MoreOnProduct\Step1.png</clipname>
</clipbin_object>

To keep things simple, I copied (Introduction.camproj) to the folder where all screenshots were present under directory images/

Opened Introduction.camproj in gvim and triggered the following command

:%s/C:\\Users\\power\\Desktop\\MoreOnProduct\\Step1.png/images/g

It reflected as:
<clipbin_object>
<clipname>images\Step1.png</clipname>
</clipbin_object>

Finally I got the video to the original state.

Scrolling with row Headings Fixed - in Spreadsheet

2009-03-18T11:04:00.000-07:00

Was quite happy to learn this tonight :)

Select cell in Excel sheet (OpenOffice calc) and Click on Window > Freeze,
this way you can make the rows below the selected cell scroll beneath it.

1. For Horizontal Freeze - Select only first cell

2. For Horizontal & Vertical Freeze - Select any other cell.

For Reference: http://www.learnopenoffice.org/CalcTutorial13.htm

Turning On Mysql Query Logging

2009-01-09T04:09:00.000-08:00

Edit mysql configuration file (my.cnf, like /etc/my.cnf) and the add an entry under mysqld section

[mysqld]
log = /var/log/mysqld-all.log

Follow the steps given below:

1. chown mysql:mysql /var/log/mysqld-all.log

2. chmod o-r /var/log/mysqld-all.log

3. /etc/init.d/mysqld restart

Now when you execute sql you should see the log :)

Happy New Year 2009

2009-01-02T01:51:00.000-08:00

Wish you a

Created this 3D Text Image from Inkscape
(Reference Article)

VMware on Fedora Core 7

2007-11-04T22:45:00.000-08:00

I have put up documentation on getting VMware Setup on Fedora Core 7, you can get it download it from here.

SVN - Trac - Apache Setup

2007-10-29T06:35:00.000-07:00

I have put up a small documentation on achieving the SVN - Trac setup with Apache,
you can download it from here.

Update: Added information of setting up read-writer permission for SVN through Access file version2 here.

diffdir - compute diff between directory

2007-09-12T00:00:00.000-07:00

Use this application if you want to compute difference between two directories
and create filter out files that has modifications or newer in the source directory.

It is available on code.google.com subversion http://diffdir.googlecode.com/svn/

You can download the application here.

Useful Windows Tools

2007-09-09T04:36:00.000-07:00

Sticky Notes For Windows:
StickyNotes
* Add a note and right on it to find more options!
* You can customize each note.
* Set Alarm
* Load and Save Notes from File.
* And Many More... see documentation

http://hottnotes.com/
ttp://sourceforge.net/projects/s-notes/

Alarm Clock:
by Cinnamon Software

*nix utilities
Commonly used *nix commands for windows:
UnxUtils @sourceforge or UnxUtils

Check out most popular tools here:
Open Source For Mac and Windows

Learn more about Equivalent Linux Software on Windows

Skype doesn't let Apache Start!

2007-09-06T23:45:00.000-07:00

We found any issue with Apache startup when Skype is up.

Skype by default uses port 80 and port 443 for incoming connections,

unfortunately we want the same ports used for Apache in general.

You can change the preferences of Skype to work on different port in the preferences,
(Tools -> Options)

and keep your Apache running on port 80 or 443.

Some references:
http://hasin.wordpress.com/2007/06/28/damn-why-the-hell-skype-is-blocking-port-80/

[Thanks for Puneeth to figure out about changing skype preference on port]

Lanuchy - Keystoke launcher for windows

2007-09-05T22:31:00.000-07:00

Launchy is a very cool tool for windows.

ALT+SPACE any where will bring up the launchy.

Right Click on Launchy window,
* You can configure Directory to index for searching and
also set the extensions to look for!
* Hotkey - configure it if you want Launchy to appear other than ALT+SPACE

ESC will push back Launchy.

Learn more on using launchy here.

[Are you on linux? Then have a look at katapult.

Database Comparsion - dbdiff

2007-08-21T01:05:00.000-07:00

If you are looking for database comparision tool, try this dbdiff from RubyForge.

Setting up Repository

2007-07-23T05:13:00.000-07:00

CVS

Steps to follow to setup CVS:

1. mkdir /home/cvsfolder
2. export CVSROOT=/home/cvsfolder
3. cvs init
Initialize your cvs folder

4. chown -R ownername:groupname /home/cvsfolder
5. chmod -R g+rwxs /home/cvsfolder
This is a important step. Here we are making the directory sticky.
When a user commits a file to cvs, the username might change but the
groupname still remains the same.

If you don't follow this step, you might end up in a situation where a developer
checks in the file and other developer can't commit the same file.

Import Project to CVS

1. mkdir /project/TestProject
2. touch /project/TestProject/README.txt
3. export CVSROOT=/home/cvsfolder
4. cd /project/TestProject
5. cvs import -m "Some initial comment on the project" TestProject youcompany release_tag

Your TestProject is in CVS now.

Checking out the from CVS

1. export CVSROOT=/home/cvsfolder
2. cvs checkout TestProject

Checking out from Remote Server CVS

1. export CVS_RSH=ssh
2. cvs -d:ext:yourname@server.com:/home/cvsfolder checkout TestProject

Flash Object and z-index.

2007-07-02T22:49:00.000-07:00

If you are working with Flash and HTML you will sooner or later run in to problems of overlay.
Find more details on

TechNote

Flash content and z-index.

Experimenting with Flash content and z-index.

MXML Autocomplete In Eclipse

2007-06-07T04:25:00.000-07:00

I got autocompletion working while editing mxml file in eclipse, here are the few simple steps to follow:

1. First look if you have mxml2.xsd file in the flex installation directory. If you don't have
then get it here.

[NOTE: If you don't have webtools for eclipse, you will have to install it, follow the method suggested in Step 1 in the link
for your eclipse version.]

2. Window -> Preferences -> Web And XML -> XML Catalog
Add User Specified Entries
URI:
Key Type: Namespace Name (Its autofilled)
Key : http://www.adobe.com/2006/mxml (Its autofilled)

3. Window -> Preferences -> General -> Editors -> File Association
Add File Types: *.mxml (Click on Add next to listed file preferences and add it)
Associate Editor: XML Editor (Click on Add under Associate editors and select it)

4. Window -> Preferences -> General -> Content Types
Under Text Edit -> XML, Add *.mxml

You should get drop down list if you do: <mx: type CTRL+SPACE within
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
</mx:Application>

References:
http://www.straker.co.nz/shadozoom/blog/2005/editing-mxml-files-with-eclipse-3.1.cfm
http://cfsilence.com/blog/client/index.cfm/2007/3/26/Setting-Up-Eclipse-For-Flex-2

Roner - Rounded Corner Generator

2007-05-18T00:17:00.000-07:00

I was inspired by the article google's own cornershop and wanted something similar application that we could integrate with our application (or server).

Came across this article later, Rounded and Shaded Corners

Modified the source Tapestry Contrib, fixed few transparency bug and enhanced few more options.

This project is on google's Subversion Repository reach it via http://roner.googlecode.com/svn/

Roner Documentation

Compact Policy For Cookies

2007-05-15T00:04:00.000-07:00

If your website has an iframe and its pointing to someother website, the cookie restriction is applied for that iframe. Please look into the reference's below, if not you might end up wasting lot of time to figure out why things work on Firefox but not on IE.

http://www.w3.org/TR/P3P/
http://www.sitepoint.com/article/p3p-cookies-ie6/2
http://www.duxcw.com/faq/webmastr/privhttp.htm
http://www.microsoft.com/windows/ie/ie6/using/howto/privacy/config.mspx
http://www.w3.org/TR/P3P/#guiding_principles
http://www.eder.us/projects/p3p-gen/
http://www.oreillynet.com/pub/a/javascript/2002/10/04/p3p.html

Look at the source code, to get more information about P3P Header: http://www.eder.us/projects/p3p-gen/p3p-gen.tar.gz

Business Card SMS

2007-04-18T23:00:00.000-07:00

Recently I was asked to send a Business Card via Mobile, I had no chance of trying such a thing earlier though in theory I knew what it was. Did some homework and got to know what is it finally :)

Send Business Cards

With this handy tip you can save your friends the trouble of storing your numbers.

A business card is a special SMS message which is composed as follows:
//SCKE2 BEGIN:VCARD N:name TEL:number END:VCARD

The receiver will see the text BUSINESS CARD RECEIVED displayed on his/her. phone.

For more information look at SMS tips

StopWatch -- A Mobile Java Application

2007-04-08T23:04:00.000-07:00

A simple stop watch designed for mobile phones supporting MIDP-2.0 and CLDC-1.1

Simply copy the StopWatch.jar file to your mobile, via DataCable/Bluetooth/Infrared.

Start the application and you should see it working.
I have tested it on Nokia 6030, Let me know if you had any feedback.

This project is on google's Subversion Repository reach it via http://stop-watch.googlecode.com/svn/

Using stmp.gmail.com To Send Mail

2007-03-29T01:43:00.000-07:00

Here is a snippet of code I wrote to use smtp.gmail.com to send mails.
Please use vaild email address.

import org.apache.commons.mail.DefaultAuthenticator;
import org.apache.commons.mail.Email;
import org.apache.commons.mail.EmailException;
import org.apache.commons.mail.SimpleEmail;

/**
 * @author prasad
 */
public class MailInfo {
    public void send() throws EmailException {
        Email email = new SimpleEmail();
        String authuser = "--------@gmail.com";
        String authpwd  = "**********";
        // Very Important, Don't use email.setAuthentication()
        email.setAuthenticator(new DefaultAuthenticator(authuser, authpwd));
        email.setDebug(false); // true if you want to debug
        email.setHostName("smtp.gmail.com");
        email.getMailSession().getProperties().put(
           "mail.smtp.starttls.enable", "true");

        email.setFrom("++++++++@gmail.com", "SenderName");

        email.setSubject("TestMail");
        email.setMsg("This is a test mail?");
 
        email.addTo(".......@gmail.com", "ToName");
        email.send();
    }
}

JavaProxy -- HTTP Proxy In Java

2007-03-28T01:52:00.000-07:00

I decided to write this JavaProxy as I was looking for a proxy similar to CGIProxy implemented in Java.

After checking out HTMLParser library,
I got my implementation of JavaProxy working. Here is the download link.

Just copy the JavaProxy.war file into your Tomcat/webapps folder and you should be able to use it,
using http://localhost:8080/JavaProxy/

I have released it under Apache License 2.0, so make the best use of it.
Let me know if you liked it or found some use in your application.

I have got this project on google's Subversion Repository http://java-proxy.googlecode.com/svn/

[NOTE: Steps to import your project on code.google.com
To host your project on googlecode, signin for an account at http://code.google.com/hosting/

Create a new project (myproject).

Go to MyProfile (note down Username) and under Settings (note down Password).

From your terminal type (assuming your are under project folder):
svn import -m "Initial Import" . https://myproject.googlecode.com/svn/trunk --username Username
You will be prompted for Username and Password, enter the one you had notedown.
Now your code is in subversion repository.
]

Eclipse Profiler Plugin

2007-03-11T23:44:00.000-07:00

Was looking for eclipse profile plugin and got this link: http://eclipsecolorer.sourceforge.net/index_profiler.html
Download link is here.

I could not get the plugin working with eclipse-3.2 but I could see the Profiler perspective as described when I tried with eclipse-3.1.

When I tried to run the profiler I got some error like this:
Plug-in unable to load class ru.nlmk.eclipse.profiler was unable to load class
ru.nlmk.eclipse.profiler.launch.ProfilerLaunchConfigurationDelegate.

Check out more discussion on this problem here.

I tried to use the bug fixed plugin for eclipse-3.1, use this link.

After getting this patched version of plugin:
1. Unzip it to eclipse/plugin folder.
2. For windows:
Copy ProfilerDLL.dll to ${JAVA_HOME}/jre/bin folder

For Linux Box:
Get libProfilerDLL.so from native/profiler_linux.tgz and copy it to libProfilerDLL.so in native/profiler_linux.tgz to ${JAVA_HOME}/jre/lib/i386/

[NOTE] I had to recompile a new version of libProfilerDLL.so. Its simple to do. Just set the right path for your java installation in the shell script m [you get it after untaring native/profiler_linux.tgz], execute it (you will need right permission to copy the shared library)

Shell script m (used to recompile and copy libProfilerDLL.so)

#!/bin/sh
export JAVA_HOME=/usr/java/j2sdk1.4.2_06

g++ -O0 -DLINUX -shared -Wall -I. -I${JAVA_HOME}/include -I${JAVA_HOME}/include/linux ProfilerDLL.cpp -o libProfilerDLL.so
cp libProfilerDLL.so ${JAVA_HOME}/jre/lib/i386/libProfilerDLL.so

Enjoy Profiling!

Are you hit by Email-Worm?

2007-03-11T22:52:00.000-07:00

My System got affected by Email-Worm.Win32.Brontok Virus few months back from now.
Although Anti-Virus cleaned up this worm, but I had to spend sometime to get the system configuration back to normal. Here are few links which helped me in the process.

Email-Worm.Win32.Brontok Virus:
http://activepanel.blogspot.com/2006/01/brontok-rontokbro-korbo-b-mytob-virus.html

and more about similar virus W32.Rontokbro@mm:
http://drvamsikrishna.blogspot.com/2007/02/solution-for-folder-options-missing_28.html

My system configuration has landed to proper state, I can now breathe easy, (Quite successfully avoided usual Windows RE-INSTALL!)

Tomcat Cache Control Customization

2007-02-28T21:55:00.000-08:00

In the last post Customize Tomcat's Static File Serving we discussed how to customize file serving in our application.

If we allow Tomcat DefaultServlet to serve the static resource, it sends back ETag header which is used for cache control on the client browser. The problem with this is client (browser) will send request to check if the file is modified each time we refresh the page. This will add overhead to our application as well as server.

We might want to completely avoid client browser (if cache is enabled) from requesting a resource until sometime, in such case right cache control headers should be sent back. Here is our new CustomFileServlet which add custom cache headers if the resource served is javascript or css file and such resource will asked to cache for a day.

package com.example.servlet;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.catalina.servlets.DefaultServlet;

public class CustomFileServlet extends DefaultServlet {
    private static final long serialVersionUID = 1L;
    public void doPost(HttpServletRequest request, 
                       HttpServletResponse response)
    throws IOException, ServletException {
        if (processRequest(request, response)) {
            super.doPost(request, response);
        }
    }
    public void doGet(HttpServletRequest request, 
                      HttpServletResponse response)
    throws IOException, ServletException {
        if (processRequest(request, response)) {
     super.doGet(request, response);
        }
    }    
    public boolean processRequest(HttpServletRequest request, 
                               HttpServletResponse response) 
    throws IOException, ServletException {
     String requestURI = request.getRequestURI();
     String contextPath = request.getContextPath();
     
     String fileURI = "";
        if (requestURI.indexOf(contextPath) != -1) {
            // Request URI is CONTEXTPATH + RESOURCE URI
            fileURI = requestURI.substring(
                        requestURI.indexOf(contextPath) 
                        + contextPath.length());
        }

        File file = new File(request.getSession()
                             .getServletContext().getRealPath(fileURI));
        String lowerfile = file.getAbsolutePath().toLowerCase();

        boolean isBasePath = "/".equalsIgnoreCase(fileURI);
     boolean isJSFile = lowerfile.endsWith(".js");
     boolean isCSSFile = lowerfile.endsWith(".css");
     boolean customServing = (!isBasePath) && (isJSFile || isCSSFile);

        if(customServing) {
            String mimetype = request.getSession()
                              .getServletContext().getMimeType(fileURI);
            response.setContentType(mimetype);

            // Required Cache Control Headers
            String maxage = "86400"; // One day in Seconds
            response.setHeader("Cache-Control", "max-age="+ maxage);
         long relExpiresInMillis = System.currentTimeMillis() + (1000 * Long.parseLong(maxage));
         response.setHeader("Expires", getGMTTimeString(relExpiresInMillis));
            response.setHeader("Last-Modified", getGMTTimeString(file.lastModified()));
 
            // Serve the file content
            FileInputStream fis = new FileInputStream(file);
            OutputStream ostream = response.getOutputStream();
            streamIO(fis, ostream);
            fis.close();
            ostream.flush();
            ostream.close();

            return false; // We have taken care of file serving.
        }
        return true; // Let DefaultServlet handle file serving
    }
    public static String getGMTTimeString(long milliSeconds) {
        SimpleDateFormat sdf = new SimpleDateFormat("E, d MMM yyyy HH:mm:ss 'GMT'");
     return sdf.format(new Date(milliSeconds));
    }
    public static void streamIO(InputStream is, OutputStream os)
    throws IOException {
        byte[] bytes = new byte[2048];
        int readlen = -1;
        while ((readlen = is.read(bytes)) != -1) {
            os.write(bytes, 0, readlen);
            os.flush(); // Let us flush after bluk write
        }
    }

Customize Tomcat's Static File Serving

2007-02-28T21:41:00.000-08:00

Tomcat maps the static file request to DefaultServlet class (org.apache.catalina.servlets.DefaultServlet in Tomcat/server/lib/servlets-default.jar).

If you want to customize file serving the following steps need to be followed.
1. Mapping in web.xml for you application

<servlet>
  <servlet-name>CustomFileServlet</servlet-name>
  <servlet-class>com.example.servlet.CustomFileServlet</servlet-class>
    <init-param>
      <param-name>listing</param-name>
      <param-value>true</param-value>
    <!-- allow browsing directory inside web application -->
</servlet>
<servlet-mapping>
    <servlet-name>CustomeFileServlet</servlet-name>
    <url-pattern>/</url-pattern>  
    <!-- Maps all request except the ones which are mapped separately -->
</servlet-mapping>

2. Enable privilege for the application (since server library class is used).
Here is an example context file I created for such a application (Tomcat/conf/Catalina/localhost/customapp.xml)
<?xml version="1.0"?>
<context path="/customapp" docbase="/home/prasad/CustomApp/web" privileged="true" reloadable="true"></context>

3. Write a CustomFileServlet class.

package com.example.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.catalina.servlets.DefaultServlet;
public class CustomFileServlet extends DefaultServlet {
    private static final long serialVersionUID = 1L;
    public void doPost(HttpServletRequest request, 
       HttpServletResponse response)
    throws IOException, ServletException {
        if (processRequest(request, response)) {
         super.doPost(request, response);
        }
    }

    public void doGet(HttpServletRequest request, 
      HttpServletResponse response)
    throws IOException, ServletException {
        if (processRequest(request, response)) {
 super.doGet(request, response);
        }
    }
    
    public boolean processRequest(HttpServletRequest request, 
               HttpServletResponse response) 
    throws IOException, ServletException {
     String requestURI = request.getRequestURI();
     String contextPath = request.getContextPath();
     
     String fileURI = "";
            if (requestURI.indexOf(contextPath) != -1) {
                // Request URI is CONTEXTPATH + RESOURCE URI
                fileURI = requestURI.substring(
                         requestURI.indexOf(contextPath) + 
                         contextPath.length());
            }
 
 boolean checkPassed = false;
 // DO SOME CHECKS BEFORE SERVING FILE...

        return checkPassed; 
    }

mod_gzip for Apache

2006-12-14T21:20:00.000-08:00

Apache's mod_gzip provides good compression for server output. I just got it working on my server with little bit of tweaking done in the configuration. I was using the debian server.

Install mod_zip if you don't have it already:

apt-get install libapache-mod-gzip

Load the module mod_gzip: (add this line in httpd.conf or modules.conf)
LoadModule gzip_module /usr/lib/apache/1.3/mod_gzip.so
Look at the example http://schroepl.net/projekte/mod_gzip/config.htm configuration file.

Here is the configurtaion I added:

<IfModule mod_gzip.c>
  mod_gzip_on                   Yes
  mod_gzip_can_negotiate        Yes
  mod_gzip_static_suffix        .gz
  AddEncoding              gzip .gz
  mod_gzip_command_version      '/mod_gzip_status'
  mod_gzip_keep_workfiles       No
  mod_gzip_minimum_file_size    500
  mod_gzip_maximum_file_size    500000
  mod_gzip_maximum_inmem_size   60000
  mod_gzip_handle_methods        GET POST

  mod_gzip_item_exclude         reqheader  "User-agent: Mozilla/4.0[678]"

  mod_gzip_item_include         file       \.html$

  mod_gzip_item_include         file       \.js$
  mod_gzip_item_include         file       \.css$

  mod_gzip_item_exclude         mime       ^image/
  mod_gzip_item_include         mime       ^text/

  # This was very important to get things working
  mod_gzip_item_include         uri        .*

  mod_gzip_dechunk              Yes

  LogFormat                     "%h %l %u %t \"%V %r\" %<s %b 
mod_gzip: %{mod_gzip_result}n In:%{mod_gzip_input_size}n -< 
Out:%{mod_gzip_output_size}n = %{mod_gzip_compression_ratio}n 
pct." common_with_mod_gzip_info2

  CustomLog               /var/log/apache/mod_gzip.log common_with_mod_gzip_info2
</IfModule>

I had to add the configuration line mod_gzip_item_include uri .* until then I saw only mod_gzip: DECLINED:EXCLUDED In:0 -< Out:0 = 0 pct. in the mod_zip.log.
Look at http://www.debian-administration.org/articles/31 which reports problem with mod_gzip and mod_ssl, so added this line of configuration as well. Add this only if you enabled ssl access for your server.

<VirtualHost *:443>
  <IfModule mod_ssl.c>
   ...
  </IfModule>

  <IfModule mod_gzip.c>
      mod_gzip_on No
  </IfModule>
</VirtualHost>

NOTE: With Apache2 you can use mod_deflate for the gzip compression. To get more details look at
http://httpd.apache.org/docs/2.0/mod/mod_deflate.html

Locale Dependent DateFormat

2006-12-14T04:12:00.000-08:00

Recently I came across a strange problem on the debian server install.

The following piece of jython code which was working fine on my machine failed to work on debian server.

import java.text.DateFormat as DateFormat
format = DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.MEDIUM);
format.setLenient(1);
print format.parse('Nov 6, 2006 3:23:54 PM');

I was getting this exception:

Traceback (innermost last):
  File "<string>", line 5, in ?
java.text.ParseException: Unparseable date: "Nov 6, 2006 3:23:54 PM"
 at java.text.DateFormat.parse(DateFormat.java:335)
        ...

I looked at the default Locale that was used and it was: [command used: locale]

LANG=en_IN
LC_CTYPE="en_IN"
LC_NUMERIC="en_IN"
LC_TIME="en_IN"
LC_COLLATE="en_IN"
LC_MONETARY="en_IN"
LC_MESSAGES="en_IN"
LC_PAPER="en_IN"
LC_NAME="en_IN"
LC_ADDRESS="en_IN"
LC_TELEPHONE="en_IN"
LC_MEASUREMENT="en_IN"
LC_IDENTIFICATION="en_IN"
LC_ALL=

I did the following and got the piece of code working:

export LC_CTYPE="en_US.UTF-8"

[If this does not solve try export LC_TIME="en_US.UTF-8"]

After this I could got the following output:

Mon Nov 06 15:23:54 IST 2006

Make sure you set the right LOCALE before using any API that depends on SYSTEM LOCALE information. Few Java API's allows you to specify the Locale as an argument use it when required.

More details about Java 1.3 Locale

I found a related post Don't forget to specify the locale

StackOverflowError When Instantiating A Class

2006-11-29T20:18:00.000-08:00

Try out this small piece of code and you can see JVM reports StackOverflowError.

public class FirstClass {
    public FirstClass() {
        SecondClass secondClass = new SecondClass();
    }

    public static void main(String[] args) {
        /* Instanstiating FirstClass ends with StackOverflowError */
        FirstClass firstClassInstance = new FirstClass();
    }
}
public class SecondClass {
    public SecondClass() {
        FirstClass firstClassInstance = new FirstClass();
    }
}

We are trying to instantiate FirstClass object inside main function, FirstClass constructor tries to instantiate SecondClass object and SecondClass constructor tries to instantiate FirstClass object which ends up in a busy endless situation and hence StackOverflows.

Although this is not a common situation of programming, such mistakes or piece of code will be hard to figure out especially when writing Web Application where things are little hard to debug.

If you like to look at the source of this example, check out here.

Javascript Function Call Surprised Me

2006-11-09T22:41:00.000-08:00

I was studying the javascript function call from an iframe to its parent page.
I was taken by surprise when I observed this:

When I pass Array parameter from iframe page to its parent the instanceof function calls works quite diffrent on different browser and its version :(

I have isolated the problem in the following page:
http://www.geocities.com/prasad20002005/TestIFrameCall/parent.html

Thanks to Pramod who sent me this link: http://www.thescripts.com/forum/thread91190.html
where the same issue was discussed.

DataMashups Service Beta

2006-10-21T03:35:00.000-07:00

If you are looking for a Enterprise Mashups Tool check out DataMashups Service Beta, its available now.

Data Mashups is a "Online Service for Enterprises" from Applibase, Inc.

Update: DataMashups gets listed as "The Best Web 2.0 Software of 2006" on Dion Hinchcliffe's Blog

VirtualHost with ServerAlias

2006-09-07T02:42:00.000-07:00

I was setting up VirtualHost for my Apache server with ServerAlias, as shown below:

<virtualhost *:80>
ServerName myserver.com
ServerAlias myserver.com, *.myserver.com
DocumentRoot /path/to/directory
</virtualhost>

This was the first time I was playing with VirtualHost configuration and ServerAlias, I got http://myserver.com working but http://myname.myserver.com or http://myadmin.myserver.com were not working.

I realized I had missed one step which was stated in the documentation:
"Of course, you can't just make up names and place them in ServerName or ServerAlias. You must first have your DNS server properly configured to map those names to an IP address associated with your server."

DNS Mapping for the subdomain's was the problem. I noticed, DNS mapping was done for myserver in com domain something like this:

mysever IN A 192.168.0.XX

but there was no mapping for my subdomain's. I added a CNAME record in the DNS, something like this

*.myserver IN CNAME myserver
[Please refer to documentaion for adding CNAME DNS entry, it might vary. ]

Once I updated my DNS Server, the ServerAlias started to work.

Few of the DNS Servers I tried: Posadis, BIND .

MySql Getting LastInsertId

2006-04-29T00:54:00.000-07:00

LastInsertId refers to the unique identifier that is generated for tuple/row of the table when you do a insert into the table. You should have "AUTO_INCREMENT" column in the table to get the last insert id. MySql needs this column to be UNIQUE. The value generated for such column will start from 1.

A simple table for our discussion would be.
create table autotable (id int auto_increment unique, primary key (id));

How do you get the last insert id when you insert a tuple?

This function will try to get the last insert id information given the prepared statement (for MySql JDBC driver). If the information is not available, the -1 value is returned.

public Integer getLastInsertId(PreparedStatement ps) {
  int lastInsertId = -1;
  PreparedStatement lastInsertIdPs = 
      ps.getConnection().prepareStatement("SELECT LAST_INSERT_ID()");
  ResultSet rs = lastInsertIdPs.executeQuery();
  while(rs.next()) {
      lastInsertId = rs.getInt(1);
  }
   return new Integer(lastInsertId);
}

Let us execute the prepared statement:

PreparedStatement preparedStatement = 
  connection.prepareStatement("insert into autotable (id) values (?)");
preparedStatement.setObject(1, new Integer(1));
preparedStatement.execute(); 
Integer lastInsertId = getLastInsertId(ps);

The lastInsertId value will be 0 in this case, though MySql inserts value 1 for the auto_increment field (id) of the table.

How do we fix this mismatch?
You have to make sure you will not insert values to auto_increment field, in which case MySql generates the value and you can get the generated value using the getLastInsertId function.

So the above piece of code should be written like this:

PreparedStatement preparedStatement = 
  connection.prepareStatement("insert into autotable (id) values (?)");
preparedStatement.setObject(1, null); // Let MySql generate the value for this field
preparedStatement.execute(); 
Integer lastInsertId = getLastInsertId(ps);

lastInsertId value will now be 1 (auto generated value for this insert).

Mplay - Mplayer Console Frontend

2006-03-07T22:41:00.000-08:00

I got a chance today to try Mplay a console based frontend for MPlayer written in Perl. Its good and supports lot of options. One thing that was interesting to me: "remembers the position within the track last played before quitting" which was one of the feature I was looking for. Nothing more to say right now, just enjoying the song through it :).

Working with Sablecc

2006-03-06T22:57:00.000-08:00

After working with Antlr and Javacc I came across Sablecc which was described as
"an object-oriented framework that generates compilers (and interpreters) in the Java programming language".

I started with Etienne Gagnon's Master thesis which is quite well written. I was pretty convinced when I got my first program working with Sablecc. I decided to document the steps I followed which can serve as a tutorial to start working with Sablecc. Here is the link for my tutorial(pdf) and first application INIParser(zip)

Reference links:
Mistaeks I Hav Made
Sablecc Wiki

Resource links:
Sablecc-3-beta.3
Sablecc downloads
Sablecc Home

Extension for TrimPath

2006-02-21T22:58:00.000-08:00

Javascript Templates from TrimPath is good to work with. The documentation is quite good. It was fast and easy to get started. At the beginning I liked the idea of having the JST Template as the part of the page (hidden textarea), but it turned out that I will not be able to reuse in other pages. The suggested alternative of keeping *.jst files on the web server and load them into the browser using XMLHttpRequest sounded bit interesting.

I just extended TrimPath object by adding the function processTemplateFile, which does and XMLHttpRequest and fetch the jstfile and merge it with the context. You can pass function to get callback with processed template, response status and status text or pass dom element whose innerHTML will be updated once the template is processed.

Look at the extension I have added exttemplate.js

Example:

function mergeWithFile(trmfile, context, getcallback) {
    var resultdiv = document.getElementById("result");
    if(getcallback != null and getcallback == false)
        TrimPath.processTemplateFile(trmfile, context, resultdiv);
    else
        TrimPath.processTemplateFile(trmfile, context, handler);               
    function handler(mergedJST, status, statusText) {
        if(mergedJST == null) {
            mergedJST = "HTTP STATUS: " + status + "," + statusText;
        }
        resultdiv.innerHTML = mergedJST;
    }
}
function mergeWithoutCallback() {
  var context = { values : ["prasad", "me"] };  
  mergeWithFile("jstfiles/mytemplate.jst", context, false);
}
function mergeWithCallback() {
  var context = { values : ["prasad", "me"] };  
  mergeWithFile("jstfiles/mytemplate.jst", context);
  // Same as
  // mergeWithFile("jstfiles/mytemplate.jst", context, true);
}

Tomcat WebApplication Context File

2006-02-20T06:58:00.000-08:00

You can deploy tomcat web application by creating a <webapp>.xml file. This method is handy while you are developing the WebApplication (where you don't want to build the war file, deploy it to Tomcat/webapps) and it also allows reloading the context for the web application when any class file (in WEB-INF/classes) directory changes.
For this to work, you should have the xml file (name same as "application path"+ ".xml") in Tomcat/conf/Catalina/localhost directory, you don't need to put the war file under Tomcat/webapps.

Let say, our web application directory is "/home/prasad/apps/TestApp/web" and
we like to access it as "http://localhost:8080/testapp". Then, you have to create the "testapp.xml" in Tomcat/conf/localhost directory with the following content in it:

<xml version="1.0">
<Context path="/testapp"
docBase="/home/prasad/apps/TestApp/web"
reloadable="true" />

The reloadable attribute is the one the allows reloading of context when the class file changes. docBase attribute should point to the web directory (which has child directory named WEB-INF), otherwise Tomcat can delete the context file, as its not valid.

Creation of context file is useful when you want to secure you web application, ie. apply security constraints to access files of you web application and you want to Tomcat to use your tables to authenticate user access. Here is how you can setup Tomcat's JDBC authentication:

<?xml version="1.0"?>
<Context path="/testapp"
docBase="/home/prasad/apps/TestApp/web"
reloadable="true">
  <Realm className="org.apache.catalina.realm.JDBCRealm"
   driverName="jdbc.DatabaseDriver"
   connectionURL="jdbc:protocol:appauthdb"
   connectionName="admin" connectionPassword="admin"
   userTable="utable" userNameCol="uname" userCredCol="passwd"
   userRoleTable="rtable" roleNameCol="rname"/>
</Context>

Table Structure:
create table utable (uname varchar(255), passwd varchar(255), primary key(uname, passwd))
create table rtable (uname varchar(255), rname varchar(255))

This basically sets up Realm for this web application. [By default, there is Realm defined for entire Engine or Host in Tomcat/conf/server.xml] You are basically setting the context to use JDBC Realm and acess appauthdb database tables utable and rtable to authenticate the user.

To check out the Realm usage you have to define the security-constraint in web.xml file in (/home/prasad/apps/TestApp/WEB-INF/web.xml).

<security-constraint>
<web-resource-collection>
  <web-resource-name>Entire Application</web-resource-name>
  <url-pattern>/*</url-pattern>
</web-resource-collection>
<auth-constraint>
  <role-name>appuser</role-name>
</auth-constraint>
</security-constraint>

<login-config>
<auth-method>BASIC</auth-method>

</login-config>

We defined the security contraint for the entire web application (url-pattern) and all user with role (role-name) appuser can access the resource of web application. Once done add values to utable and rtable.

insert into utable(uname, passwd) values ('prasad', 'somepwd')
insert into rtable(uname, rname) values ('prasad', 'appuser')

When you visit, http://localhost:8080/testapp, you get a HTTP Authentication dialog box, and you can see only 'prasad' is allowed to use the application.

Hope this piece of information is useful.

IE supports Conditional Comments

2006-02-15T12:10:00.000-08:00

I came across a situation where I had to write few CSS rules (call it a hack!) to make things look the same on both IE and Firefox. I actually wrote IE specific rules in a different file with the intension to include it only when page is rendered on IE. Its quite interesting to know the support for Conditional Comments available in IE 5+.

Well the article gives the complete details about conditional comments.

Brief:
IE supports if conditional construct within the HTML comment.

Example, to include a stylesheet when HTML is displayed in IE.

Feed discovery extension

2006-02-09T02:00:00.000-08:00

Feeds available on a site is currently discovered by feed readers by looking at link rel="alternate" tag, which is present on the page:

<link rel="alternate" type="application/rss+xml"
  title="MySiteMainFeed" href="http://localhost.com/main.xml" />

The difficulty with this is, you have to specify link rel="alternate" for each of the feed available on the site. To simplify this we can have link rel="alternate" type="application/feedlist+xml" on the page which provides list of available feeds on your site.

Example:
<link rel="alternate" type="application/feedlist+xml"
  title="MySiteMainFeed" href="http://localhost.com/feedlist.xml" />

feedlist.xml will be:
<?xml version="1.0"?>
<feedlist>
  <link rel="alternate" title="RSS Content" type="application/rss+xml"
href="http://localhost.com/rss_feed.xml"/>
  <link rel="alternate" title="Atom Content" type="application/atom+xml"
href="http://localhost.com/atom_feed.xml"/>
  <link rel="alternate" title="Comment" type="application/rss+xml"
href="http://localhost.com/comment_rss_feed.xml"/>
</feedlist>

Javascript and Java Comparision

2006-01-29T23:52:00.000-08:00

When I started to work with javascript few months back, I found it to be interesting.
I was working with Java at the same time, writing some Servlet Code. I found most of the features is very simple to learn in javascript. If you are familar with Java then things are even more simpler.
I have written some sort of comparision between few things of java and javascript. Here is the link: JavascriptAndJava

Design Self Refreshing HTML Page

2006-01-24T21:32:00.000-08:00

I faced a problem in one of my WebApplication where the response from the server for the client request was taking too long, without any feedback to the client about the progress. The servlet (ClientServlet) which handled the request (for url, clientreq), spent most of its time on lookups before sending the response.

I found html meta to be useful in such case. The <meta http-equiv='refresh' content='1; url="clientreq"'> when included in HTML page will timeout the page every 1 second (specified value in content) and the request is sent to the specified url (clientreq). Taking advantage of this feature I designed a model where the client can get the feedback on the progress of the response.

The design was, ClientServlet will redirect to progress.jsp with status message if it is not ready to send response (busy in doing the lookup). Once ClientServlet has finished its lookup it sends the actual response to the client instead of redirect.

Task of progress.jsp is just to send the HTML page with the status message along with <meta http-equiv='refresh' content='1; url="clientreq"'>. Which makes frequent request to the ClientServlet to get the status or response.

The lookup work was moved to the class AsyncHandler, which spans a new thread when it is started and gives the status of its work.

First ClientServlet creates AsyncHandler and puts into the session after starting it. A redirect is sent to progress.jsp with status message. For subsequent request, ClientServlet checks the status of AsyncHandler and decides whether to redirect to progress.jsp or send actual response.

Snippet of my Servlet code:

private void processRequest(HttpServletRequest req, 
    HttpServletResponse res) throws Exception {

    final String HANDLER_KEY = "Client_Async_Handler";
    HttpSession session = req.getSession();
    AsyncHandler ah = 
       (AsyncHandler) session.getAttribute(HANDLER_KEY);

    if(ah == null) {
 ah = new AsyncHandler();
 ah.start();
 session.setAttribute(HANDLER_KEY, ah);
 res.sendRedirect("progress.jsp?msg=" +
 URLEncoder.encode(ah.getStatus(), "utf-8"));
 return;
    } else {
 if(ah.done()) {
     sendResponse(res, ah);
     session.setAttribute(HANDLER_KEY, null);
     ah = null;
     return;
 } else {
     res.sendRedirect("progress.jsp?msg=" +
     URLEncoder.encode(ah.getStatus(), "utf-8"));
     return;
 }
    }
}

Snippet of progress.jsp:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta http-equiv='refresh' content='1; url="clientreq"'>
<title>Please Wait</title>
</head>
<body>
<%= req.getParameter("msg") %>
</body>
</html>

Static Initializer in Java

2005-12-26T22:15:00.000-08:00

Let me start with a small question. (At least it was interesting to me). Go through the following lines of code.

/* Initializer.java */
package staticinit;
/**
 * A simple class to demonstrate the working of static block of code
 * that is used to initialize the static class variables.
 * @author prasad
 */
public class Initializer {
    /** Initialize the class variables. */
    public Initializer() {
        firstClassVar = "VALUE_NOT_NULL";
        secondClassVar = "VALUE_NOT_NULL";
        thirdClassVar = "VALUE_NOT_NULL";
        fourthClassVar = "VALUE_NOT_NULL";
    }   
    /** Initialize the static variables. */ 
    static {
        firstStaticVar = "STATIC_NOT_NULL";
        secondStaticVar = "STATIC_NOT_NULL";        
    }    
    /** Static variables. */
    private static String firstStaticVar = null;
    private static String secondStaticVar;    
    /** Class variables. */
    private String firstClassVar = firstStaticVar;
    private String secondClassVar = secondStaticVar;
    private String thirdClassVar = null;
    private String fourthClassVar;
    /** Examine and display the values. */
    public void display() {
        System.out.println("firstStaticVar  -> " + getValue(firstStaticVar));
        System.out.println("secondStaticVar -> " + getValue(secondStaticVar));
        
        System.out.println("firstClasssVar  -> " + getValue(firstClassVar));
        System.out.println("secondClassVar  -> " + getValue(secondClassVar));
        System.out.println("thirdClassVar   -> " + getValue(thirdClassVar));
        System.out.println("fourthClassVar  -> " + getValue(fourthClassVar));
    }    
    private String getValue(Object value) {
        return (value == null)? "is null": value.toString();
    }    
    /** Main entry point. */
    public static void main(String[] args) {
        Initializer initializer = new Initializer();
        initializer.display();
    }
}

Which of the variable(s) will have the value "null" in the function display()?
a) firstStaticVar
b) secondStaticVar
c) firstClassVar / secondClassVar / thridClassVar / fourthClassVar
d) none of the above

You are right if you had selected the option (a).

Why only firstStaticVar is "null"?

When the class is instantiated, before constructor is called the variables are defined (which takes the default value) and then the static initialization are performed inorder. The static initialization can be static block of code or inline assignment etc. In the above code, after static block of code is executed, firstStaticVar is re-assigned by the "inline assignment". Next secondStaticVar has no "inline assignment" so the previous initialized value is retained. Next all firstClassVar and thridClassVar are inline initialized. After this, the constructor is called which will re-initialize all the ClassVar's. When the constructor finishes its work only firstStaticVar will have the value "null".

Things like this can result in bugs which would be hard to figure out or debug. A simple solution would be to declare variables (with or without initialization) before any "code block" that access it.

Size in TB on a GB hard disk

2005-12-16T04:23:00.000-08:00

I was just organizing my projects that were spread across different paritions on my system over time. Here is the result that showed up when I checked size of my home parition using konqueror after all the work.

I was really taken by surprise when I saw "2TB", I have used more space than I really have (80GB) O:-) I did "du -csh /home" which showed "7.7G".

Handling Control Characters in XML

2005-10-21T05:41:00.000-07:00

I started off with my application with the decision that it will use xml to handle data communication. It was doing well for a long time, I was happy. Now the day came where my application just was getting broken as xml was not being parsed properly. Well, I had to fix the issue, but was not really happy about my decision of using xml for the kind of data I am working with. I was really sad when I tried to open the xml file isocontrol.xml in the browser and it says parsererror.

It was really had for me now, as some character was getting into xml from my application (which I had not expected). I started to fix this, I looked around the web to know more about this kind of problem. Many suggested using different encoding, tried so but could not fix it. One more solution was to encode the data in base64 encoding (as we do for binary data like images), well I was not sure should I do this as I was handling more of text in my application than binary data.

It was late in the nigth I had no other choice except to read the xml file and get to know what was that character that was causing the problem. Well, I figured out it was the character with value '6' (integer) or CONTROL-F that actually made my xml go for a toss. Now, I looked at some references which stated that control character from 0 to 31 that is not handled by most xml parsers and will lead to parser failures. So all I had was to convert the control character to entity references. So I wrote a small fix to my application. Link to Source.

/**
  * Get proper xml string value (with ISOControl characters converted to 
  * entity references)
  * @param source String which has to be converted
  * @param startTag Start tag of the xml data (null if not needed)
  * @param endTag End tag of the xml data (null if not needed)
  * @return String with ISOControl characters converted to entity references.
  */
public static String toXMLdata(String source, String startTag, String endTag) {
    StringBuffer xmldatasb = new StringBuffer();
    if(startTag != null) xmldatasb.append(startTag);
        
    if(source == null || "e;"e;.equals(source)) {
        xmldatasb.append(source);
    } else {
        for(int index = 0; index < source.length(); ++index) {
            char sourceCh = source.charAt(index);
            if(Character.isISOControl(sourceCh))
                xmldatasb.append(entityReference(sourceCh));
            else
                xmldatasb.append(sourceCh);
        }
    }
    if(endTag != null) xmldatasb.append(endTag);
    return xmldatasb.toString();
}
   
/**
  * Get the entity reference for the character.
  * @param sourceCh character whose entity reference is needed.
  * @return Entity Reference &#integer;, where integer corresponds to
  * to the number that represents sourceCh.
  */
public static String entityReference(char sourceCh) {
    return "&#" + (int)sourceCh + ";" ;
}

The few lines of code was worth a lot to my application. All it does it when it sees the iso control characters (0 to 31) it will be replaced by entity references (&#integervalue;)

Using kjParsing module.

2005-10-03T03:53:00.000-07:00

This Sunday I came across the kjParsing module, "A parser generator written in Python for Python". It is good for writing experimental translators, code generators, interpreters, or compilers. I wanted to work with it and get atleast a simple application built on it. By end of night, yep I got my "Simple Calculator Program" working :). I tried to get the Calculator program, as I get a chance to playaround defining different rules for the grammar which are very simple. Here is the Source. You can download the complete source here.

TextMarkup

2005-09-04T23:32:00.000-07:00

I was looking for some tool that would convert some kind of text markup to html. As I feel typing html is really boring when the level of tags are deep and you are left with job of closing all the tags properly. I was not using any fancy editor nor I like to use on the machine that is considered too slow for the day [I have one :(]. This led me to come up with TextMarkup, some markup rules that would help to type less html and take care of closing tags properly or atleast warn me when some tags are not closed properly. Visit TextMarkup to know more. Download TextMarkup.zip, to get conversion of markup file to html. The markup rules can be used for xml files also. Get the vim syntax plugin for textmarkup files here.

Todo WebApplication

2005-07-10T23:43:00.000-07:00

Working with VTL (Velocity Template Language) was interesting. I have designed a small web application called 'todo'. This will allow you to put up task todo and also it will allow you to delete the task that are completed. This application can also work without using velocity.

What are the features?

It is a simple web application that uses XMLHttpRequest to talk with the server.
You can configure the application to use either HttpServlet or VelocityServlet just by changing the web.xml files.
You can keep track of you task through web interface.

You can get the complete source here. You can get only the war file here.
Brief README follows, you can see the complete README file in sourcezipfile.

Put the todo.war file into Tomcat's webapp directory.
Start tomcat. Tomcat will unpack the war file into the directory (todo).
By default the web.xml file in todo/WEB-INF will use the servlets present in the package pra.code.todo.servlets.
You can make the application to use the servlets present in the package pra.code.todo.velocity, by replacing the web.xml with velocity.web.xml under the name web.xml.
You may have to restart Tomcat.

XMLMapper Utility

2005-07-01T00:52:00.000-07:00

The basic purpose of XMLMapper utility is to enable working with xml files easily using Java's lists and maps. XMLMapper will parse the xml file and creates XMLElement (root) that will contain XMLElements (children) and attributes. The xmlfile is parsed using SAXParser. Using the XMLMapper, I have written few applications like RSSFeedParser and XMLCompare which will show the usage of the utility. You can download the complete source from here .

[UPDATE: Using XMLMapper wrote a application AntReportDiff that will compare the xml report files generated for testsuite when ant is used with juint. You can download it here.To know more about the application please go through README file in it.]

Put your data inside column

2005-05-24T23:00:00.000-07:00

I came across a problem where I had to send across data in neatly formatted column (only text). I designed a small python script column.py that lets me put data in column with wordwrap and allows customization of column border.

COLUMNS IN VERTICAL DISPLAY
+------------------+
|*This.is.test.data|
+------------------+
+------------------+
|*This.is.test.....|
|datas.............|
+------------------+
COLUMNS IN HORIZONTAL DISPLAY
+------------------++------------------+
|*This.is.test.data||*This.is.test.....|
|..................||datas.............|
+------------------++------------------+

[UPDATE: I implemented report.py using column.py, which will generate formatted work report. The input for report.py is datafile. See output.]

del.icio.us "tag rename/delete" script

2005-05-17T00:49:00.000-07:00

In del.icio.us to rename a tag or delete it you have to go to your settings page. The GreaseMonkey userscript tag rename/delete user script allows you to rename or delete the tag without moving to the settings page.
When this userscript is used. After every tag, you get two links: « that allows you to rename the tag and x that allows you to delete the tag.

Snapshot of userscript at work:

Colorizer in Javascript

2005-05-10T03:22:00.000-07:00

I wrote a simple colorizer using javascript which helps you to get the colorized source code (in HTML). The language supported are: java, c, c++, c# and javascript. Click here for online access to the page. You can get the source files from here.

XML and RSS0.92 Parser

2005-04-26T03:01:00.000-07:00

Wrote a basic xmlparser module in python which can parse the xml file and returns UserDict. Using xmlparser module I implemented parsefeed module which can now parse the RSS 0.92 xml file and return UserDict which can be handled easily. You can download the modules here.

Python implementation of "tail -f"

2005-04-17T23:47:00.000-07:00

I wrote a small python script that will show the behavior of UNIX/LINUX "tail -f" command. The python script may come handy for windows users. Click tailf.zip to get the source.

Javascript - tutorial

2005-04-15T08:19:00.000-07:00

As a basic introduction to javascript, I have designed the following applications:

Introduction - Do simple mathematical calculation.
DataStructures - Understand using Array and Associative Array.
Calculator - Basic calculator application
Autohint - A text box that will suggest the available options, some thing simlar to Google Suggest TextBox
XHR - Explains using XMLHttpRequest , fetches tags of delicious user using delicious api, once you enter the delicious user name and password.
XHR integrated with Autohint text box.

You can download all the files here.Start page is login.html. When username is prompted at login, use one of the following: admin/prasad/hint/xhr/monkey.
Note: Most of the script working is specific to firefox/mozilla/netspace.

greasemonkey - feedlink with popup

2005-04-11T08:20:00.000-07:00

Today, I enhanced the functionality of feedlink. Here is the user script. Now feedlink userscript not only shows the feeds available as images, but gets you a popup menu when you click on the image and you can subscribe to aggregators like bloglines or newsgator. You can customize the popup menu, by setting proper values in the user script for:

subscriptions
MENUWIDTH
MENUHEIGHT

Here is a small snapshot showing the popup menu.

You can get the zip file here that contains the user script and many more.
If you need the version without popup or for installation help, checkout this entry.

greasemonkey - autodiscover site feed

2005-04-08T02:12:00.000-07:00

FeedLink the greasemonkey plugin will enable the autodiscovery of site feeds and display them as anchor images. Here is the user script that you can use.
Following are the steps to install the user script:

If you haven't installed greasemonkey Firefox extension. Then get it installed.
Open this user script in Firefox.
From "Tools" menu select "Install User Script..." and confirm all the prompt.
To configure the script, select "Manage User Scripts..." from "Tools" menu.
By default, User script is added for "http://www.livejournal.com/users/*" (eg:http://www.livejournal.com/users/someone) and "http://*.blogspot.com*"(eg:http://someone/blogspot.com/).

You can get the zip file here that contains the user script and many more.When site feeds are discovered it will be displayed as anchor images: (I am showing only images here)

Writing Python Module in C

2005-04-05T01:07:00.000-07:00

I have designed a module for python with the basic intension of describing how to write modules in c, install and use it. In the module (c program) that I have designed, a prompt (input to c program) will be displayed on the terminal, the user password will be read from the terminal and it will be returned as the python string object to python interpreter. You can download the module here.

Basic Python Calculator - pycalc

2005-04-01T01:36:00.000-08:00

Inspired by the first version of my calculator (in c#), I went on with the same application in python but using slightly different logic during the expression evaluation. Well, it was really challenging to sit overnight to get the code done. Get the code here.

View Algorithm

Here is the simple Algorithm that I have used:
1. Build a list of tokens from input expression.
2. Evaluate all the subexpression in the list and replace it with the result.
3. Now, evaluate the right hand side of assignment operator (if present) 
   and replace it with result.
4. Finally, evaluate the remaining expression in the list.

View Output

The Calculator output:
[prasad@prasad pycalc]$ ./pycalc.py
Basic Calculator Application, from Prasad.A
Type 'quit' to terminate
>>> pi=22/7
>>> rad=15
>>> area=pi*(rad*rad)
>>> area
707.142857143
>>> quit

Basic Calculator Application

2005-03-30T23:43:00.000-08:00

With the intension of building simple parser I made a move to get calculator application that supports variables and dynamic value fetch etc. Well I am falling short of text to put into here to describe my excitement. I am putting below the source code so that you can try it out. The application is written in C#.
Feedback and Suggestions are most welcome (Use comments to express them). Download

View Calculator Code

/**
* Basic Calculator Application
* Author: Prasad.A
*/
using System;
using System.Collections;
namespace ConsoleCalculator {
 /* Basic Calculator Class */
 public class BaseCalculator {
   /* Dictionary to store variables and its values */
   private IDictionary _dictionary = null;
   /* Stack to carry out the operations */
   private Stack operationStack = null;   
   /* Default Constructor */
   public BaseCalculator() {
     this._dictionary = new Hashtable();
     Console.WriteLine("Basic Calculator Application");
     Console.WriteLine("Type 'quit' to terminate.");
   }   
   /* Get the substring of the string */
   private String GetSubString(String expression,int start,int end) {
     return expression.Substring(start,(end-start));
   }   
   /* Push element on to operation stack */
   private void Push(Object element) {
     operationStack.Push(element);
   }       
   /* Pop element from the operation stack */
   private Object Pop() {
     if(operationStack.Count > 0) return operationStack.Pop();
     return null;
   }   
   /* Peek element from the operation stack */
   private Object Peek() {
     if(operationStack.Count > 0) return operationStack.Peek();
     return null;
   }         
   /* Evaluate the expression within '(' and ')' */
   private void EvaluateSubExpression() {     
     Object element = Pop(); /* This is just behind ')' */
     while(element != null && element.ToString().CompareTo("(") != 0) {
       /* Get result from binary evaluation */
       Object binaryEvaluation = BinaryEvaluate(element);
       element = Pop(); /* This will be the operator for next iteration */
       /* Did we get start of sub expression */
       if(element.ToString().CompareTo("(")==0) {
         /* Push the result and break out of loop */
         Push(binaryEvaluation);
         break;
       }
       /* Push back the operator that was popped */
       Push(element);
       /* Now one of the operand is the result itself */
       element = binaryEvaluation;
     }
   }   
   /* Evaluate the expression */
   private Object EvaluateExpression() {
     Object result = null;
     Object element = Pop(); /* This is operand two */
     while(element!=null) {
       /* Get result from binary evaluation */
       result = BinaryEvaluate(element);
       /* If we have reached end of stack, break */
       if(Peek() == null) break;
       /* Opearand two is result itself */
       element = result;
     }
     return result;
   }   
   /* Evaluate the binary expression, the input parameter is operand2,
    * Get the operator element and operand1 from stack. If operator element
    * or operand1 is not present do a unary operation else if operator element
    * is = then do a assignment operation else do a binary evaluation.
    */ 
   private Object BinaryEvaluate(Object operandTwo) {
     Object evalBinary = new Object();
     Object operatorElement = null;
     Object operandOne = null;           
     if(Peek() != null &&
        Peek().ToString().CompareTo("(")!=0)
       operatorElement = Pop();        
     if(operatorElement != null &&
        Peek() != null &&
        Peek().ToString().CompareTo("(")!=0)
       operandOne = Pop();        
     if(operatorElement!=null &&
        operatorElement.ToString().CompareTo("=")!=0) {
       operandTwo = GetObjectValue(operandTwo);
       operandOne = GetObjectValue(operandOne);
     }
     if(operatorElement==null)
       evalBinary = GetObjectValue(operandTwo);
     else if(operandOne==null) {
       if(operatorElement.ToString().CompareTo("+")==0)
         evalBinary = (+1.0)*double.Parse(operandTwo.ToString());
       else if(operatorElement.ToString().CompareTo("-")==0)
         evalBinary = (-1.0)*double.Parse(operandOne.ToString());
     }
     else {
       switch(operatorElement.ToString()) {
         case "+":
           evalBinary = double.Parse(operandOne.ToString())+
           double.Parse(operandTwo.ToString()); break;
         case "-":
           evalBinary = double.Parse(operandOne.ToString())-
           double.Parse(operandTwo.ToString()); break;
         case "*":
           evalBinary = double.Parse(operandOne.ToString())*
           double.Parse(operandTwo.ToString()); break;
         case "/":
           evalBinary = double.Parse(operandOne.ToString())/
           double.Parse(operandTwo.ToString()); break;
         case "=":
           SetIdValue(operandOne.ToString(),operandTwo.ToString());
           evalBinary = null; break;
       }
     }
     return evalBinary;
   }   
   /* Parse the input string and evaluate as and when required */
   private Object parse(String expression) {
     operationStack = new Stack();
     int parsePointer = 0; /* Points to beginning of token */     
     bool inIdentifier = false,inNumber = false;
     for(int index=0; index < expression.Length; ++index) {
       char ch=expression[index];
       /* We got a identifier or number delimiter */
       if(ch == ' ' || ch == '\t') {
         if(inIdentifier) {
           Push(GetSubString(expression,parsePointer,index));
           parsePointer = index+1;
           inIdentifier = false;
         }
         if(inNumber) {
           Push(GetSubString(expression,parsePointer,index));
           parsePointer = index+1;
           inNumber = false;
         }
       }
       /* We got start of sub expression */
       else if(ch=='(') {
         Push(ch.ToString());
         parsePointer = index+1;
       }
       /* We got end of sub expression */
       else if(ch == ')') {
         if(inIdentifier) {
           Push(GetSubString(expression,parsePointer,index));
           parsePointer = index+1;
           inIdentifier = false;
         }
         if(inNumber) {
           Push(GetSubString(expression,parsePointer,index));
           parsePointer = index+1;
           inNumber = false;
         }
         EvaluateSubExpression();         
       }
       /* We got assignment operator */
       else if(ch=='=') {
         if(inIdentifier) {
           Push(GetSubString(expression,parsePointer,index));           
           inIdentifier = false;
         }
         Push(ch.ToString());
         parsePointer = index+1;
       }
       /* We got arithmetic operator */
       else if(isOperator(ch)) {
         if(inIdentifier) {
           Push(GetSubString(expression,parsePointer,index));           
           inIdentifier = false;
         }
         if(inNumber) {
           Push(GetSubString(expression,parsePointer,index));
           inNumber = false;
         }
         Push(ch.ToString());         
         parsePointer = index+1;
       }
       /* We got a letter and we are not in identifier */
       else if(Char.IsLetter(ch) && !inIdentifier) {
         inIdentifier = true;
       }
       /* We got a digit and we are not in number */
       else if(Char.IsDigit(ch) && !inNumber) {
         inNumber = true;
       }
       /* We got a decimal point */
       else if(ch=='.') {
         if(index < expression.Length-1 &&
            !Char.IsDigit(expression[index+1])) {
           Push(GetSubString(expression,parsePointer,index));
           parsePointer = index+1;
           inNumber = false;
         }
       }
       /* We are in identifier and we got a identifier delimiter */
       else if(inIdentifier && isIdDelimiter(ch)) {
         Push(GetSubString(expression,parsePointer,index));
         parsePointer = index+1;
         inIdentifier = false;
       }
       /* We are in number and we got a number delimiter */
       else if(inNumber && isNumberDelimiter(ch)) {
         Push(GetSubString(expression,parsePointer,index));
         parsePointer = index+1;
         inNumber = false;
       }
     }
     /* Are we still in identifier */
     if(inIdentifier)
       Push(GetSubString(expression,parsePointer,expression.Length));
     /* Are we still in number */
     else if(inNumber)
       Push(GetSubString(expression,parsePointer,expression.Length));
     /* Let us return the result of expression */
     return EvaluateExpression();
   }   
   /* Decide on the identifier delimiter */
   private bool isIdDelimiter(char delim) {
     if(delim=='.'||delim=='('||delim==')') return true;
     return isOperator(delim);
   }
   /* Decide on the nubmer delimiter */
   private bool isNumberDelimiter(char delim) {
     if(delim=='('||delim==')') return true;
     return Char.IsLetter(delim);
   }
   /* Decide on the operator */
   private bool isOperator(char delim) {
     if(delim=='+'||delim=='-'||delim=='*'||delim=='/'||delim=='=')
       return true;
     return false;
   }   
   /* Get the value of input object
    * return either number or variable value)
    */
   private Object GetObjectValue(Object inputObject) {
     Object valueObject = null;
     try {
       valueObject = GetNumberObject(inputObject.ToString());
     } catch(FormatException fe) {
       valueObject = GetIdValue(inputObject.ToString());
     }
     return valueObject;
   }   
   /* Return the numeric representation of input string */
   private Object GetNumberObject(String inputString) {
     Object numberObject = null;
     try {
       numberObject = int.Parse(inputString);
     } catch(FormatException fei) {
       try {
         numberObject = double.Parse(inputString);
       } catch(FormatException fed) {
         throw new FormatException("Error! Illegal number format");
       }
     }
     return numberObject;
   }   
   /* Set the variable and its value in _dictionary */

   private void SetIdValue(String id,String val) {
     Object number = null;
     try {
       number = GetNumberObject(val);
     } catch(FormatException fe) {
       number = GetIdValue(val);
     }
     if(number != null) _dictionary[id] = number.ToString();
   }   
   /* Get the value of the variable from _dictionary */
   private Object GetIdValue(String id) {
     Object idValue = _dictionary[id];
     if(idValue != null) return idValue;
     throw new Exception("Error! Variable '"+id+"' not yet defined");
   }   
   /* Core function to keep the interaction alive */
   public void RunCalculator() {
     while(true) {
       Console.Write(">>> ");
       String input = Console.ReadLine();
       if(input.CompareTo("quit")==0)
         break;
       try {
         Object result = parse(input);
         if(result != null)
           Console.WriteLine(result.ToString());
       } catch(Exception ex) {
         Console.WriteLine(ex.Message);
       }
     }
   }
 } 
 /* A user class that contains the main function
  * To give life to calculator */
 public class UserCalculator {
   public static void Main(string[] args) {
     BaseCalculator bc = new BaseCalculator();
     bc.RunCalculator();
   }
 }
}

View Calculator Output

Basic Calculator Application
Type 'quit' to terminate.
>>> a=10.5
>>> b
Error! Variable 'b' not yet defined
>>> b=20
>>> b
20
>>> c=a+b
>>> c
30.5
>>> d=10.1+(b*c)/a
>>> d
68.1952380952381
>>> quit

WordPress filter Colorizer (PraColorizer)

2005-03-18T03:27:00.000-08:00

I have written filter plugin for WordPress that will colorize your java,c++,c,c# code that you will put in the post. You can download from here.
To know more about PraColorizer click here.
You can also get information at wp-plugins.net

pracut filter at wp-plugins.net

2005-03-17T07:53:00.000-08:00

I have updated the pracut filter for wordpress at wp-plugins.net. To know more about pracut tag see this entry.

WordPress filter for pracut tag

2005-03-15T22:14:00.000-08:00

Hey, I have written filter plugin for WordPress. You can download from here. To know more about pracut tag click here.

Toggle Content Display

2005-03-09T21:46:00.000-08:00

I have been using a small snippet of my html design that uses css and javascript to toggle the display of content that is under it. I use it to toggle the source code, the output, etc. I am putting the html code under the toggle below, check it out and feel free use it.

View Html Code

<span id="vid" 
style="text-decoration:underline;display:inline;cursor:pointer;color:blue;" 
onclick="this.style.display='none';document.getElementById('hid').style.display='inline'; 
document.getElementById('sid').style.display='block';">
<b>View Html Code</b></span>
<span id="hid" style="text-decoration:underline;display:none;cursor:pointer;color:blue;" 
onclick="this.style.display='none';document.getElementById('vid').style.display='inline'; 
document.getElementById('sid').style.display='none';">
<b>Hide Html Code</b></span>
<div id="sid" style="display: none;"><pre>
Here goes my content[ NOTE: Please take care keep the id (vid,hid,sid) unique ]
</pre></div>

Colorizer: For C#, Java, C, C++

2005-03-09T05:39:00.000-08:00

This Colorizer is implemented in C#. The implementation of colorizer basically started of to be a good choice to demonstrate the use of regular expression (atleast the basic) and few useful syntax the C# provides, like inside the swtich statement, the handling of dictionary. You can use this colorizer to colorize the java, c, c++ or c# code. Before I end this entry let me tell one small thing [I used the same colorizer to colorize the source shown below :)]. Download

View Colorizer.cs

// Author: Prasad.A
using System;
using System.Collections;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;


namespace CSharpUtils {
 // Class that describes keywords and creates a dictionary
   // lookup depending on the language selection.
   class CKeyword {
   // Dictionary to lookup the keyword.
     private IDictionary keydict = null;

  // Java language keywords

    protected string[] jkeywords = {
    "abstract", "default", "goto", "package", "synchronized",
    "boolean", "do", "if", "private", "this",
    "break", "double", "implements", "protected","throw",
    "byte", "else", "import", "public", "throws",
    "case", "enum", "instanceof", "return", "transient",
    "catch", "extends", "int", "short", "try",
    "char", "final", "interface", "static", "void",
    "class", "finally", "long", "strictfp", "volatile",
    "const", "float", "native", "super", "while",
    "continue", "for", "new", "switch"

  };
  // C# language keywords
    protected string[] cskeywords = {
    "abstract", "event", "new", "struct",
    "as", "explicit", "null", "switch",
    "base", "extern", "object", "this",
    "bool", "false", "operator", "throw",
    "break", "finally", "out", "true",
    "byte", "fixed", "override", "try",
    "case", "float", "params", "typeof",
    "catch", "for", "private", "uint",
    "char", "foreach", "protected","ulong",
    "checked", "goto", "public", "unchecked",
    "class", "if", "readonly", "unsafe",
    "const", "implicit", "ref", "ushort",
    "continue", "in", "return", "using",
    "decimal", "int", "sbyte", "virtual",
    "default", "interface","sealed", "volatile",
    "delegate", "internal", "short", "void",
    "do", "is", "sizeof", "while",
    "double", "lock", "stackalloc",
    "else", "long", "static",
    "enum", "namespace","string"

  };
  // C language keywords
    protected string[] ckeywords = {
    "auto", "double", "int", "struct",
    "break", "else", "long", "switch",
    "case", "enum", "register", "typedef",
    "char", "extern", "return", "union",
    "const", "float", "short", "unsigned",
    "continue", "for", "signed", "void",
    "default", "goto", "sizeof", "volatile",
    "do", "if", "static", "while"

  };
  // C++ language keywords
    protected string[] cppkeywords = {
    "asm", "auto", "bool", "break", "case",
    "catch", "char", "class", "const", "continue",
    "default", "delete", "do", "double", "else",
    "enum", "explicit", "extern", "false", "float",
    "for", "friend", "goto", "if", "inline",
    "int", "long", "mutable", "namespace",
    "new", "operator", "private", "protected", "public",
    "register", "return", "short", "signed", "sizeof",
    "static", "struct", "switch", "template", "this",
    "throw", "true", "try", "typedef", "typeid",
    "typename", "union", "unsigned", "using", "virtual",
    "void", "volatile", "while"

  };

  // Default Language is C#
    public CKeyword() { initKeyDict("c#"); }
  // Set the user specified language
    public CKeyword(string language) { initKeyDict(language); }

  // Initialize the keyword lookup dictionary

    public void initKeyDict(string language) {
    string[] initKeywords = null;

    if(language=="c#"||language==null) initKeywords = cskeywords;
    else if(language=="java") initKeywords = jkeywords;
    else if(language=="c") initKeywords = ckeywords;
    else if(language=="c++") initKeywords = cppkeywords;

    keydict = new Hashtable();
    for(int i=0; i < initKeywords.Length; ++i) {
      keydict[initKeywords[i]] = "";
    }
  }
  // Check whether the given word is a keyword

    protected bool isKeyword(String word) { return keydict.Contains(word); }
}

// Class that will do the coloring of input file
  class Colorizer : CKeyword {
  private bool inDocumentation = false; // Are we inside the documentation

    private bool inComment = false; // Are we inside the comment
    private string filename = null; // File under processing

    private bool completeHtml = false; // Should the output be complete html

  // Default constructor
    public Colorizer() { }

  // Constructor to set the language type and output type

    public Colorizer(string language,bool completeHtml) : base(language) {
    this.completeHtml = completeHtml;
  }

  // Actual function that will colorize the input file and dumps the
    // output to output file (if null then standard output will be used)

    public void colorize(string infile,string outfile) {
    // Set the file name under process.
      filename = infile;

    StreamReader instream = new StreamReader(filename);

    // Set the console output to file if outfile is specified

      if(outfile != null) Console.SetOut(new StreamWriter(outfile));

    // If output should be complete html put the headers
      if(completeHtml) writeHtmlHeaders();

    // Parse each line and the process it
      for(string line; (line = instream.ReadLine()) != null; ) {
      bool doParse = true;
      while(doParse) {
        IDictionary dictionary = parseLine(line);
        dictionary["line"] = line;
        line = processResult(dictionary);
        if(line == null) doParse = false;
      }
    }
    // If output is complete html put the footers

      if(completeHtml) writeHtmlFooters();

    // Close the output stream
      if(outfile != null) Console.Out.Close();
  }

  // Write starting html tags
    private void writeHtmlHeaders() {
    Console.Write("<html><head><title>"+filename+"</title>");
    Console.Write("<style type='text/css'>");
    Console.Write(".body { font: 10pt Verdana, sans-serif; }");

    Console.Write(".keyword { color: blue;} ");
    Console.Write(".comment { color: green;} ");
    Console.Write(".document { color: #777777;} ");
    Console.Write(".string { color: brown;} ");
    Console.Write("</style>");
    Console.WriteLine("</head>");
    Console.Write("<body><pre>");
  }

  // Write ending html tags

    private void writeHtmlFooters() {
    Console.Write("</pre></body></html>");
  }

  // Parse each line of input
    private IDictionary parseLine(string line) {
    // Core pattern that will break the line into token

      string pattern = @"(/\*\*?)|(\*/)|(//)|(\w+)|([ \t\r\n]+)|("".*"")|([^*/\w\t\r\n ])|([/\*])";

    // Get the token
      Match match = Regex.Match(line,pattern);
    // Set the result as dictionary
      IDictionary dictionary = new Hashtable();
    dictionary["index"] = match.Index;
    dictionary["length"] = match.Length;
    return dictionary;
  }

  // Process the match

    private string processResult(IDictionary dictionary) {
    int index = (int) dictionary["index"];
    int length = (int) dictionary["length"];
    string line = (string) dictionary["line"];

    if(length==0) { Console.WriteLine(); return null; }
    else {
      return processToken(line.Substring(index,length),
      line.Substring(index+length));
    }
  }

  // Process the token

    private string processToken(string token,string remenant) {
    bool inline = true;
    switch(token) {
      case "/*":
        inComment = true;
        if(completeHtml) Console.Write("<span class='comment'>");
        else Console.Write("<span style='{color:green;}'>");

        Console.Write(convertToHtml(token));
        break;
      case "/**":
        inDocumentation = true;
        if(completeHtml) Console.Write("<span class='document'>");
        else Console.Write("<span style='{color:#777777;}'>");
        Console.Write(convertToHtml(token));
        break;
      case "*/":
        Console.Write(token);
        if(inComment || inDocumentation) Console.Write("</span>");
        inComment = inDocumentation = false;
        break;
      case "//":
        if(completeHtml) Console.Write("<span class='comment'>");
        else Console.Write("<span style='{color:green;}'>");

        Console.WriteLine(convertToHtml(token+remenant));
        Console.Write("</span>");
        remenant=null;
        break;
      default:
        if(inComment || inDocumentation) Console.Write(token);
        else {
          if(base.isKeyword(token)) {
            if(completeHtml)
              Console.Write("<span class='keyword'>");
            else Console.Write("<span style='{color:blue;}'>");

              Console.Write(convertToHtml(token));
              Console.Write("</span>");
          }
          else if(token.StartsWith("\"") && token.EndsWith("\"")) {
            if(completeHtml)
            Console.Write("<span class='string'>");
            else Console.Write("<span style='{color:brown;}'>");

            Console.Write(convertToHtml(token));
            Console.Write("</span>");
          }
          else

            Console.Write(convertToHtml(token));
        }
        break;
    }
    return remenant;
  }

  // Format the text to put as html
    private StringBuilder convertToHtml(string text) {
    StringBuilder sb = new StringBuilder(text);
    sb = sb.Replace("<","&lt;");
    sb = sb.Replace(">","&gt;");
    return sb;
  }

  // Display the version and exit

    private static void printVersion() {
    Console.WriteLine("Colorizer, Version 1.0, Author: Prasad.A");
    System.Environment.Exit(0);
  }

  // Display the help and exit
    private static void printHelp() {
    Console.WriteLine("Usage: ");
    Console.WriteLine("mono Colorizer.exe [-l language] [-o outputfile] [--html] [--help,-h] [--version,-v] inputfile");
    Console.WriteLine("-l: Language selection, one of them [c# java c c++]");
    Console.WriteLine("-o: Output file name, (default to standard output)");
    Console.WriteLine("--html: For complete html output.");
    Console.WriteLine("-h, --help: This help.");
    Console.WriteLine("-v, --version: Version and Author information.");

    System.Environment.Exit(0);
  }

  private static String getLanguage(String language) {
    String specifiedLang = language.ToLower();
    if( String.Compare("c#",specifiedLang) == 0 ||
        String.Compare("java",specifiedLang) == 0 ||
        String.Compare("c",specifiedLang) == 0 ||
        String.Compare("c++",specifiedLang) == 0 ) {
      return specifiedLang;
    } else {
      Console.WriteLine("Unsupported language: "+language);
      Console.WriteLine("Supported language: c#, java, c, c++");
      System.Environment.Exit(1);
      return null;
    }
  }
  // Main function to run the Colorizer.

    public static void Main(string[] args) {
    string language = null;
    string inputfile = null;
    string outputfile = null;
    bool completeHtml = false;

    // Handle command line arguments

      if(args.Length > 0) {
      for(int i = 0; i < args.Length; ++i) {
        switch(args[i]) {
          case "-o":
            if(i < args.Length-1) outputfile = args[++i];
            else printHelp();
            break;
          case "-l":
            if(i < args.Length-1) language = getLanguage(args[++i]);
            else printHelp();
            break;
          case "--help": printHelp(); break;
          case "-h": printHelp(); break;

          case "--version": printVersion(); break;
          case "-v": printVersion(); break;

          case "--html": completeHtml = true; break;

          default: inputfile = args[i]; break;
        }
      }
    }
    // If input file is not specified, print help and exit

      if(inputfile == null) printHelp();

    // Start the colorizer after initalization
      Colorizer colorizer = new Colorizer(language,completeHtml);
    colorizer.colorize(inputfile,outputfile);
  }
}
}

xmllint --shell in Python

2005-03-02T22:59:00.000-08:00

After looking at xmllint tool in linux and giving a small introductory talk on it I came to decision to start of its implementation in python that can serve as basic introduction to xml handling in python. For this I used minidom module of python's xml.dom library which is pretty simple to understand for the starters. The program I have desgined will implement very few option of xmllint --shell. This version of python implementation targets python programmer who is unfamiliar with the minidom module of python.

xmlsh.py code follows:
View xmlsh.py

""" A basic implementation of (xmllint --shell)
Author: Prasad.A
"""

import sys
from xml.dom import minidom
from readline import *

class xmlsh(object):
   """The base class which holds the xml document."""

   def __init__(self,xmlfile):
       self.filename=xmlfile
       self.__loadFile()

   def __loadFile(self):
       self.xmlDoc = minidom.parse(self.filename)

   # Get the element from the dom (currentElement)
   def __getElement(self,elemname,currentElement,index=0):
       if(elemname==""): return (currentElement,1)
       elementList = currentElement.getElementsByTagName(elemname)
       return (elementList[index],len(elementList))

   # Handler for cat command
   def __catHandler(self,path,currentElement):
       if(path[0]=="/"): #absolute path is used
           element=self.xmlDoc
           path=path[1:]
       else: # relative path is used
           element=currentElement

       parentElement = None
       count=-1
       pathSplit = path.split("/")
       if(len(pathSplit)>1):
           for elemname in pathSplit[:len(pathSplit)]:
               parentElement = element
               (element,count) = self.__getElement(elemname,element)
       else:
           (element,count) = self.__getElement(pathSplit[-1],element)

       if(count != -1 and count > 1):
           for index in range(count):
               (element,count) = self.__getElement(pathSplit[-1],parentElement,index)

       print element.toxml()

   # Display the help
   def __printHelp(self):
       print """
The following commands are supported:
  cd [xpath]: Change to the given node.
 cat [xpath]: See the content.
 pwd        : Current position in the document.
help        : Displays this help.
This implementation will support only very basic xpath.
"""
   # Wrapper for displaying help
   def help(self):
       self.__printHelp()

   # Main loop to run the program
   def run(self):
       print "Type bye or quit to terminate."
       stop = False
       prompt = "/"
       self.currentElement = self.xmlDoc

       while(stop!=True):
           try:
               # Accept the input
               inputLine = raw_input("%s%s " % (prompt,">"))
               # If the input is empty or newline do nothing
               if(inputLine == "" or inputLine == "\n"): continue
               # Split the input
               inputSplit = inputLine.split()

               # Assume the first element of split is command
               command = inputSplit[0]
               # Adjust the arguments passed
               arguments=None
               if(len(inputSplit) > 1): arguments = "".join(inputSplit[1:])

               # Command is not still handled
               commandHandled =False

               # Handle "bye" or "quit" command
               if(command=="bye" or command=="quit"):
                   commandHandled=True
                   stop=True
                   continue

               # Handle "cd" command
               if(command=="cd"):
                   commandHandled=True
                   inputArg=arguments

                   if(arguments[0]=="/"):
                       arguments=arguments[1:]
                       self.currentElement=self.xmlDoc

                   element=self.currentElement
                   parentElement=None
                   count = -1
                   pathSplit=arguments.split("/")
                   if(len(pathSplit) > 1):
                       for elemname in pathSplit[:len(pathSplit)-1]:
                           parentElement=element
                           (element,count)=self.__getElement(elemname,element)
                   parentElement=element
                   (element,count)=self.__getElement(pathSplit[-1],element)
                   whichOne=-1
                   if(count!=-1 and count>1):
                       print count, " elements of ", pathSplit[-1]," is present."
                       whichOne = raw_input("Specify the index to select: ")

                       if whichOne != " ":
                           whichOne = int(whichOne)
                           (element,count) = self.__getElement(pathSplit[-1],parentElement,whichOne-1)
                       else:
                           element=parentElement

                   self.currentElement=element

                   separator="/"
                   if(inputArg[0]=="/"):
                       prompt=""
                       separator=""
                   elif(prompt=="/"):
                       prompt=""
                       separator="/"

                   if(whichOne==-1): prompt="%s%s%s" % (prompt,separator,inputArg)
                   else: prompt="%s%s%s[%d]" % (prompt,separator,inputArg,whichOne)

                   if(self.currentElement==None):
                       stop=True
                       continue

               # Handle "cat" command
               if(command=="cat"):
                   commandHandled = True
                   if(arguments != None): self.__catHandler(arguments,self.currentElement)
                   else: print self.currentElement.toxml()

               # Handle "pwd" command
               if(command=="pwd"):
                   commandHandled = True
                   print prompt

               # Handle "help" command
               if(command=="help"):
                   commandHandled = True
                   self.__printHelp()

               if(commandHandled==False):
                   print "Unknown Command:"
                   print self.__printHelp()

           except Exception, ex:
               print "Exception: ",ex

# Start the shell
if(len(sys.argv)>1):
   ob=xmlsh(sys.argv[1])
   print "Object created...function run() will be invoked..."
   ob.help()
   ob.run()
else:
   print "Usage: python", sys.argv[0], "xmlfilename"

A small example follows that will explain the usage of this tool.
View Usage

XML File: xmlsh.xml 
<?xml version="1.0"?>
<root>
    <element>
        <item>
            <title>Title of item1</title>
            <description>Description of item1</description>
        </item>
        <item>
            <title>Title of item2</title>
            <description>Description of item2</description>
        </item>
        <item>
            <title>Title of item3</title>
            <description>Description of item3</description>
        </item>
        <item>
            <title>Title of item4</title>
            <description>Description of item4</description>
        </item>
    </element>
</root>
Usage: python xmlsh.py xmlsh.xml
/> cat
/> cd root
/root> cd /root/element
/root/element> cat
/root/element> cd item
[Specify the index: 1]
/root/element/item[1]> cat
/root/element/item[1]> cd /root/element
/root/element> pwd
/root/element> cd item
[Specify the index: 2]
/root/element/item[2]> cd /
/> bye

Funny HelloWorld Program

2005-02-28T23:47:00.000-08:00

Today, Sidharth came up with the HelloWorld program which looked really interesting. But, it used the feature of PrintStream.printf() function that is provided by jdk1.5 and I decided to port it to jdk1.4 and used the library hb16.zip from http://www.braju.com/download/index.html to get the code working.

View Source

/**
 * This program is written to save the input parameter of 
 * a program for future use.
 * It uses the library provided by http://www.braju.com/ for printf()
 */

import java.io.PrintStream;
import java.io.FileOutputStream;
import java.io.OutputStream;

/* 
 * hb16.zip  from http://www.braju.com/
 * contains set of classes to provide printf() function
 */
import com.braju.format.Format;
import com.braju.format.Parameters;

public class HelloWorld {
  static String quote = "Hello World!";

  static String code =
    "import java.io.PrintStream;" +
    "import java.io.FileOutputStream;" +
    "import java.io.OutputStream;" +
    "import com.braju.format.Format;" +
    "import com.braju.format.Parameters;" +
    "public class HelloWorld{" +
    "static String quote=*%s*;" +
    "static String code=*%s*;" +
    "public static void main(String args[]) throws Exception {" +
    "if(args.length==1)quote = args[0];System.out.println(quote);" +
    "OutputStream os = new FileOutputStream(*HelloWorld.java*);" +
    "PrintStream ps = new PrintStream(os);" +
    "ps.println("+
    "Format.sprintf(code.replace('%c', (char)34), "+
    "new Parameters(quote).add(code).add((char)42)));" +
    "ps.close();" +
    "Runtime.getRuntime().exec(*javac -classpath hb16.zip HelloWorld.java*);" +
    "}}";

    public static void main(String args[]) throws Exception {
        if (args.length == 1) quote = args[0];
        System.out.println(quote);
        OutputStream os = new FileOutputStream("HelloWorld.java");
        PrintStream ps = new PrintStream(os);
        ps.println(Format.sprintf(code.replace('*', (char) 34), 
          new Parameters(quote).add(code).add((char) 42)));
        ps.close();
        Runtime.getRuntime().exec("javac -classpath hb16.zip HelloWorld.java");
    }
}

Compile: javac -classpath hb16.zip HelloWorld.java
Execute: 
(For Linux)   java -cp .:hb16.zip HelloWorld
(For Windows) java -cp .;hb16.zip HelloWorld
Sample:
$ java -cp .:hb16.zip HelloWorld
Hello World!
$ java -cp .:hb16.zip HelloWorld Parameter
Parameter
$ java -cp .:hb16.zip HelloWorld
Parameter
/* Parameter which was the previous input to the program has been saved. */

First python program

2005-02-22T21:55:00.000-08:00

With a excellent introduction to python language I started working on python and today I thought I will dedicate the first python program of mine to Sidharth Kuruvila LJUserInfo
Though this program is not essentially any worth(my opinion), I am still happy because it is my first program :)
People really interested can go ahead to have look at the source and comment on it.

View Python source

I created a small program Evaluate.py:


def functionCreator(choice):
   """Create the function and return it depending on choice."""
   if(choice==1):
       print "Create function for evaluating x*y+z ..."
       func = lambda x,y,z: x*y+z
   elif(choice==2):
       print "Create function for evaluating x*y-z ..."
       func = lambda x,y,z: x*y-z
   elif(choice==3):
       print "Create function for evaluating x*y*z ..."
       func = lambda x,y,z: x*y*z
   elif(choice==4):
       print "Create function for evaluating x*y**z ..."
       func = lambda x,y,z: x*y**z
   # return the generated function
   return func

# A class which defines a default function definition to evaulate its variables
# It also allows user to change the function definition at runtime so the class
# behaviour to evaulate its variables changes.
class Evaluate(object):
   """ Allow evaluation of 3 class variables with custom function at runtime."""

   def __init__(self,x,y,z):
       """Initializer which takes 3 variables x,y,z"""
       self.x = x #self.__dict__["x"] = x
       self.y = y #self.__dict__["x"] = y
       self.z = z #self.__dict__["x"] = z

   def evaluate(self,x,y,z):
       """ A default function definition to evaluate the variables.
       This function definition is configurable at runtime."""       
       return x+y+z

   def func(self):
       """ Call this function to evaluate the variables of the class
       This will delegate the work to evaluate function."""
       print "%s: %f" % ("Result",self.evaluate(self.x,self.y,self.z))

   def change(self):
       """ This function will allow user to configure the function definition
       of evaluate."""

       print "Available function generation for evaluating expression..."
       print "1. x*y+z"
       print "2. x*y-z"
       print "3. x*y*z"
       print "4. x*y**z"

       choice = int(raw_input("Please enter your choice(1,2,3,4): "))

       # Change the evaluate function defintion
       self.__dict__["evaluate"] = functionCreator(choice)

       # Inform user that the function definition was changed and can view the change
       print "Please try object.func() to see the change in evaluation."
     
# Testing for this module
if __name__ == "__main__":
   print "Evaluate Module loaded..."

I executed the script using IDLE and here were some of the actions I proceeded with some actions and got the results:
View Python output


>>> exeval=Evaluate(10,20,30)
>>> exeval.func()
Result: 60.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 1
Create function for evaluating x*y+z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 230.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 2
Create function for evaluating x*y-z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 170.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 3
Create function for evaluating x*y*z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 6000.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 4
Create function for evaluating x*y**z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 10737418239999999609046623630827404132352.000000
>>>

Never miss a space.

2005-01-27T01:59:00.000-08:00

I was till now, trying XSLT on Firefox.

I used to have a XML generated by a application that had to print the
<?xml-stylesheet type="text/xsl" href="somefile.xsl"?>
that would instruct the application of XSL Transformation on this XML.

I had a tough time to figure a small mistake of not having the space between the type value and href tag. My application would produce
<?xml-stylesheet type="text/xsl"href="somefile.xsl"?>

Firefox would still apply the XSL transformation to this XML. But I found that IE showed the whole document as XML. It was a really hard to figure what went wrong in IE that was perfectly fine in Firefox as it was really too late of the day and I was also looking at some other issue.

Yes, finally I had a zoom in look at the XML rendered in IE and surprisingly found a missing space in between the type tag value and href tag.

Yes, now I fixed the problem by adding a space and IE applied the XSL Transformation perfectly.

Beware, IE looks even for a space to validate :)

ContentType problem!

2005-01-27T01:07:00.000-08:00

I was working with java servlet that would produce XML document for which I would later apply XSLT
to display the HTML on the client side.

I made a small mistake that was really hard to find out when I was trying on IE.

The IE (I was using) would display XML document by applying XSLT correctly when I requested my server to send the document first two times but when I requested for the third time then the server would send the XML document but now IE would not display it by applying XSLT. :(

Now, I went and checked whether the XML missed out the stylesheet instruction, NO I HAD.

Now, I checked whether the stylesheet is correct and it is pointing to the correct location on server, YES IT IS.

Now, I checked the same application with same actions on Firefox.

Surprised, to see that same action in Firefox would display XML document applying XSLT any number of times I send the request.
Oh, finally I fixed the problem, the server application, that is my java servlet, missed to set the content type of the response, (HttpServletResponse)response.setContentType("text/xml"); and this was the whole cause of the rendering problem.

Now, I was really surprised to see how the first two request was being shown correctly using XSLT and not the third one. :)

GreaseMonkey Plugin.

2005-01-27T01:03:00.000-08:00

Hey, GreaseMonkey (http://greasemonkey.mozdev.org/) is really a cool extension to firefox. Using this you can customize the website you want, with your javascript.

For example:
On loading/reloading of the page (http://mail.yahoo.com) you can write a simple javascript to set the desired user name in the login box and install the script using greace monkey. And when you load the http://mail.yahoo.com you can see your java script in action.

It is quite simple to install the user java script.
(First get the grease monkey plugin installed).
1. Write a java script file having extension "user.js"
For example:

(function myOnLoad() {document.login_form.login.value="yahooId";})();

2. Open the file in the firefox.
3. Click Tools -> Install User Script
4. In the Dialog box, Edit the entry with "*" and type http://mail.yahoo.com specifying that you are installing the javascript for http://mail.yahoo.com page and press OK.
5. Open the page http://mail.yahoo.com

You can see that 'YahooId' is displayed in Login

Thats so simple. Enjoying exploring other things. :)

Get started with XML

2005-01-20T13:34:00.000-08:00

I wanted to get hold of some good reference to understand XML and know more about how is it being parsed how do we get the data into an application. I found few links that is really cool, that has some stuff that helps to get started with XML.

Understand XML:
http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/overview/index.html

Using SAX API:
http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/sax/index.html

Using DOM API:
http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/dom/index.html

Using XSLT:
http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/xslt/index.html