Igor Madjeric

Few days ago I had very interesting task. Our customer required that we perform checking of so called file's "magic numbers" to determinate does uploaded file correspond to it's extension.  We are already allowed only to upload files with some predefined extensions (PDF, DOC ...). But this can not prevent some evil user to update an exe file after renaming it to PDF or DOC. So first of all I will explain what are "magic numbers", and then I will show how we handle them.

In my previous post I've described the alphabet conversion, and I've mentioned that we used AspectJ to resolve that task, but i did not mention how AspectJ works and what are aspects generaly. So in the next few lines i will explain: what is Aspect Oriented Programming and why we need it what is AspectJ using AspectJ with Spring (configuring AspectJ and spring to work together) and i will explain aspects on the example from previous post.

In one of company's last projects we supposed to implemented support for usage of Latin and Cyrillic alphabet. This could sounds like an easy task, the Java have a real good support for the multi language application, but what is with languages which have multiple alphabets. When I said supporting more alphabets, I mean on possibility of choosing between different keybord layouts, not only on showing messages from different properties files, also content saved in database should be transformed from one to other alphabet. To accomplish these requirements, we made few decisions. We've decided to save data in Latin form and then transform it in Cyrillic if it is needed. This also mean that complete input from user side will be transformed to latin alphabet. I've almost forgot to mention technologies used in this project. It is a web application, devloped with next technologies: JSP + Servlet for front end Spring + Hibernate as backend and it is running on Tomcat 6 ...

These days one of my colleagues had problems with sending event invitation using mail templates with seam (version 2.x). In basic this should not be a hard task, so I will in short explain what need to be done for sending event invitation using seam mail templates. When you send mail invitation you need to send an email with attachment which contains information about particular event. I will create simple template and sender class which will be used for sending invitation.

Through this tutorial i will try to get you closer to the Java Servlet Model. Before we start with examination of classes defined within the servlet specification, i will explain basic stuff needed to know before you start with developing web application.

Generally speaking Listener are objects which are used for performing some action when somethings is happened. They receive notification about some change and perform action registered for that event. Also in the web application from time to time some "interesting" changes happens, and it would be nice that we can be notified about them.  Because of that in the servlet api are defined some Listener interfaces which allow us to handle events which are interesting for us.

Few months ago, during working on one of the company project, we had need to developed  REST services which is used for sending an email depending on data sent by client application. During developing this service we decide to create simple workflow engine which will be charged for sending an email, but also this engine can be used for any kind of simple flows. In this article i will explain step by step how you can implement your simple workflow engine which can handle sequence flow.

From time to time we have need to send an e-mail from application. This task should not be so complicated, but if you do it for the first time you can get some troubles and it can take you some time. Because of that I will try to explain how you can configure it correctly.