DigiZol

Data Encryption Decryption using AES Algorithm, Key and Salt with Java Cryptography Extension

noreply@blogger.com (Kamal Mettananda) — Wed, 07 Oct 2009 15:51:00 +0000

In this tutorial we will implement a full data encryption decryption cycle with Java (only data, not file encryption); encrypt some data using a secret key, salt and iterations and decrypt using the same parameters. We are using the Java Cryptography Extension (JCE) for data encryption/decryption...

[Ant] Build .WAR files in Eclipse for Web Applications

noreply@blogger.com (Kamal Mettananda) — Tue, 28 Jul 2009 13:17:00 +0000

Eclipse JEE versions support Java Web Application projects, but other Eclipse versions do not. Java developers need to build WAR (web archive) files for deployments (yes, Exploded deployments are also possible). However Eclipse does not provide a direct way to create war files; developers write ant...

[Tomcat] validateJarFile(servlet-api.jar) - jar not loaded. Offending class: javax/servlet/Servlet.class

noreply@blogger.com (Kamal Mettananda) — Thu, 09 Jul 2009 13:28:00 +0000

org.apache.catalina.loader.WebappClassLoader validateJarFile INFO: validateJarFile(<APP_PATH>\WEB-INF\lib\servlet-api.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class. We are using Apache Tomcat to deploy web applications, and getting...

Attempted to lock an already-locked dir: Subversion issue

noreply@blogger.com (Kamal Mettananda) — Wed, 08 Jul 2009 17:01:00 +0000

"Attempted to lock an already-locked dir" - svn: Working copy locked; this message is frequently faced by users of SubVersion (SVN) source repository. The message is self explanatory; simply some source files are locked and no commit or update operations allowed on those files/folders. In some...

Tomcat + Apache HTTP: Servers Connecting Guide

noreply@blogger.com (Kamal Mettananda) — Wed, 05 Nov 2008 12:01:00 +0000

Apache Tomcat is a Servlet/JSP container and used to deploy dynamic Java contents like JSPs and Servlets. Tomcat has some web server capabilities, however it is not a full blown web server to serve high traffic web sites. In the meantime Apache HTTP server is a full blown web server. So in general...

Unable to load dynamic library php_curl.dll: Error message in PHP

noreply@blogger.com (Kamal Mettananda) — Wed, 15 Oct 2008 11:48:00 +0000

In Windows, while trying to use "curl" extension with PHP 5.2/Apache 2; you may encounter a blank page. If you open up the error log file in Apache (%APACHE_HOME%\logs\error.log); you may see an error message as follows. "PHP Warning: PHP Startup: Unable to load dynamic library...

Manage HTTP headers with Java Servlets: Quick Notes

noreply@blogger.com (Kamal Mettananda) — Wed, 15 Oct 2008 11:43:00 +0000

In Java Servlets API, both HttpServletRequest and HttpServletResponse interfaces (in javax.servlet.http package) provide methods to programatically manipulate HTTP headers. There are a number of standard HTTP headers exchanged between a web server and a client (eg: a browser). "Content-Type" is a...

Google redirect to incorrect country domain: Fix on Firefox

noreply@blogger.com (Kamal Mettananda) — Wed, 08 Oct 2008 11:33:00 +0000

Google servers identify the country of the googler and redirect to the relevant country domain. They may be using the IP of the request to locate the country before the redirect. However there are situations many googler getting redirected to incorrect country domains. For example, even though our...

Gmail Multiple Sessions Alert: This account is open in 1 other location

noreply@blogger.com (Kamal Mettananda) — Tue, 23 Sep 2008 11:56:00 +0000

"This account is open in 1 other location at..." Gmail user interface provides this message when your account is used in multiple locations simultaneously. One of the most important and interesting security feature that any web mail service would wish to provide. I suppose Gmail is the only web...

Sun suspends NetBeans IDE DVD Starter Kit distribution program

noreply@blogger.com (Kamal Mettananda) — Wed, 17 Sep 2008 03:01:00 +0000

Sun has suspended their NetBeans IDE DVD Starter Kit distribution program indefinitely. Yes, you read it correctly; they have done it. So many developers used to get most of Sun (free) products through the distribution program. Students with less bandwidth (in some colleges & universities);...

Lazy loading vs. pre-loading beans with Spring Framework

noreply@blogger.com (Kamal Mettananda) — Tue, 09 Sep 2008 12:16:00 +0000

Spring framework can instantiate and bind (called loading) related Java objects (called beans) according to a given configuration. An XML file can easily be used to define these bindings. Spring framework supports two different types of loading methods; lazy loading and pre-loading respectively...

[Eclipse] Access restriction: Class is not accessible due to restriction on required library

noreply@blogger.com (Kamal Mettananda) — Tue, 09 Sep 2008 12:00:00 +0000

"Access restriction: Class is not accessible due to restriction on required library"; error message may be shown while developing Java projects in Eclipse IDE. Error message is self-explanatory, some classes can not be loaded into the project since restriction rules are being imposed on those...

Chrome or Firefox - which browser to choose?

noreply@blogger.com (Kamal Mettananda) — Thu, 04 Sep 2008 13:14:00 +0000

Chrome is the newest baby in browser family or the next competitor in browser war. What ever it is, Google released their browser named Chrome. But Mozilla Firefox is the most popular browser in the world right now and Google was the major supporter for Firefox. Even while supporting it, they have...

Use "object" instead of "bean" in Spring Configuration XML

noreply@blogger.com (Kamal Mettananda) — Wed, 03 Sep 2008 11:42:00 +0000

Spring configuration xml is used for defining the wiring between different object. It has the following format. <beans> <bean id=".." class="..."> ... </bean> ... <beans> Classes specified in the configuration file will be instantiated by Spring...

Google Web Toolkit (GWT) & Servlets - Web application tutorial

noreply@blogger.com (Kamal Mettananda) — Tue, 02 Sep 2008 12:20:00 +0000

Google Web Toolkit (GWT) and Java Servlets used in one web application. This tutorial will take you though the steps of developing a simple web application with Google Web Toolkit and J2EE Servlet Technology. The application will have a servlet on server side and one web page. PrerequisitesBetter...

Is Partitioning a hard disk into multiple drives bad?

noreply@blogger.com (Kamal Mettananda) — Wed, 27 Aug 2008 11:59:00 +0000

Hard disk partitioning is almost a must, according to what I have heard so far from my colleagues and other professionals (may be same for you). I am used to partition a hard disk at least to three drives; "C" for OS (Operating System), "D" for programs and "E for other files like documents,...

Cellspacing vs cellpadding - Table attributes comparison

noreply@blogger.com (Kamal Mettananda) — Thu, 21 Aug 2008 12:43:00 +0000

In HTML Tables (<table>) there are two attributes named, cellpadding and cellspacing. What is the different between cellpadding and cellspacing? Both these are capable of creating some empty space inside a table. cellspacing : space between cells cellpadding : space between the cell border...

If Michael Phelps is a country himself alone

noreply@blogger.com (Kamal Mettananda) — Mon, 18 Aug 2008 12:07:00 +0000

What if Michael Phelps is a country himself alone rather than representing United States of America? Michael Phelps has already gathered 8 Gold medals in Beijing Olympics 2008 including 3 relays. Most of the participating countries happened to go back empty hand, so many players are participating...

[Cricket] Most wickets in debut Test series - World record by Ajantha Mendis

noreply@blogger.com (Kamal Mettananda) — Mon, 11 Aug 2008 03:13:00 +0000

Most wickets by a player in his debut 3-match Test series; a 60+ years old world record has been broken. By whom? By Sri Lankan newly found precious mystery spinner Ajantha Mendis. He produced this new world record yesterday, 2008-08-10 with the wicket of Sachin Tendulkar, another master of...

Verify calling Javascript function available to avoid runtime errors

noreply@blogger.com (Kamal Mettananda) — Thu, 07 Aug 2008 11:55:00 +0000

Do you want to verify whether a Javascript function exists before calling it to avoid runtime errors? With Javascript we used to call Javascript functions. But sometimes our Javascript code tend to throw runtime errors and showing then on the browser. For this there can be several reasons...

Write Java with JDK 1.5 features and run on JRE 1.4

noreply@blogger.com (Kamal Mettananda) — Wed, 06 Aug 2008 12:33:00 +0000

Have you being writing your Java code on Java 1.5 (JDK 1.5) with new features like auto boxing, generics and enums? And suddenly realized that your customer's servers are still using Java 1.4 (JRE 1.4)? This is not a surprise since most of the customers are not in a position to take a risk and try...

Java: Numbers only String by removing non numeric characters

noreply@blogger.com (Kamal Mettananda) — Thu, 31 Jul 2008 12:05:00 +0000

With Java, deleting non numeric characters (letters, symbols etc) from a string to produce a numbers-only String is a common requirement in web applications, as application users are used to insert numeric values with non-numeric characters. For example a phone number will be entered with (-)...

How to open a .war (web archive) or .jar (java archive) files

noreply@blogger.com (Kamal Mettananda) — Wed, 30 Jul 2008 12:14:00 +0000

With Java we generate .JAR files to bundle a set of resources. For J2EE web applications, we generate .WAR (Web Archive) files for deployments. Both of these are ways of archiving a set of files. Both these .jar or .war archives are in zip format. So there are plenty of ways to open those files to...

Web Services with Apache Axis 1.4 Tutorial: server and client sides

noreply@blogger.com (Kamal Mettananda) — Tue, 29 Jul 2008 12:21:00 +0000

Web services are a handy method of integrating independent systems. Apache Axis is one of the best free tools available for implementing and deploying web services, and also for implementing the web service clients. In this article we will create a simple, but complete web service and a client for...

Java2WDSL & WSDL2Java - java.util.Date not handled consistently

noreply@blogger.com (Kamal Mettananda) — Wed, 16 Jul 2008 12:28:00 +0000

Java2WSDL and WSDL2Java tools in Axis (1.4) are pretty handy tools. Those help you to generate a WSDL from a java class as well as generating stubs/skeletons from a WSDL. But if you are dealing with java.util.Date fields in your code, you must pay some attention. Java2WSDLConsider the following...