Captcha for Java

       A CAPTCHA is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown on image, but current computer programs can't.
       The term CAPTCHA (for Completely Automated Public Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University.
       When u create web project sometimes u need captcha with colors of your site. That cases u can create captcha yourself as following:

Parse XML and Properties config files

       .xml(Extensible Markup Language) and .properties is a file extension for files mainly used in Java related technologies to store the configurable parameters of an application.(.properties files can also be used for storing strings for Internationalization and localization - these are known as Property Resource Bundles.)

       Let's first start with XML config files. There are many XML parser technologies, but I will show how u can use Apache Commons Configuration library to parse and use XML config files.

       The Commons Configuration software library provides a generic configuration interface which enables a Java application to read configuration data from a variety of sources:

Power of Spring's @ModelAttribute and @SessionAttributes

The Spring Framework is an open source application framework that aims to make J2EE development easier. Unlike single-tier frameworks, such as Struts or Hibernate, Spring aims to help structure whole applications in a consistent, productive manner, pulling together best-of-breed single-tier frameworks to create a coherent architecture.

How does @ModelAttribute work?
@ModelAttribute is a Spring-MVC specific annotation used for preparing the model data. It is also used to define the command object that would be bound with the HTTP request data. The annotation works only if the class is a Controller class (i.e. annotated with @Controller).

ModelAttribute can be applied on both methods as well as method-parameters. It accepts an optional "value", which indicates the name of the attribute. If no value is supplied to the annotation, then the value would be defaulted to the return type name in case of methods and parameter type name in case of method-parameters.

Spring 3 MVC Internationalization & Localization (i18n & l10N) and Reloader

In this post I will discuss about Internationalization (I18N) and Localization (L10N) in Spring 3.0 MVC. 

What is i18n and L10n?

In computing, internationalization and localization are means of adapting computer software to different languages and regional differences. Internationalization is the process of designing a software application so that it can be adapted to various languages and regions without engineering changes. Localization is the process of adapting internationalized software for a specific region or language by adding locale-specific components and translating text.

The terms are frequently abbreviated to the numeronyms i18n (where 18 stands for the number of letters between the first i and last n in internationalization) and L10n respectively, due to the length of the words. The capital L in L10n helps to distinguish it from the lowercase i in i18n. Let's begin:

Intercepting requests (annotation based request mapping)

       Spring Interceptors has the ability to pre-handle and post-handle the web requests. Each interceptor class should extend the HandlerInterceptorAdapter class. Here we will create a Login Interceptor by extending the HandlerInterceptorAdapter class. You can override any of the three callback methods preHandle(), postHandle() and afterCompletion(). As the names indicate the preHandle() method will be called before handling the request, the postHandle() method will be called after handling the request and the afterCompletion() method will be called after rendering the view.