Implementing Aspect Oriented Programming Framework - Java Instrumentation

What is Aspect Oriented Programing: Aspect Orented Programing or AOP is a design pattern or programming practice, in which the code for cross cutting concern is separated out from the main program logic, thus effectively reducing the program complexity. Now what is a cross cutting concern? They are application non-functional requirements that apply to multiple functionalities. A simple example would be logging. Logging is done whenever some predefined things happen (for example a method is invoked). Normally, every method that is invoked would have to contain the code for logging. In AOP, we write the logging code in a separate method may be in a separate class and then configure our AOP framework to do logging whenever a method is invoked. There are so many good tutorials available on AOP, one of which is here. However, in Java SE environment, it certainly requires a change in the method's byte code made by the AOP framework. I will demonstrate how an AOP framework performs load time weaving (changes byte code during runtime).

Enterprise Java Beans - A Broad Overview

What are Enterprise Java Beans: Enterprise java beans are Java EE server side business layer components. They can be used to develop highly available distributed transactional systems. Like servlets and JSPs are used to develop view components in java EE, EJBs are used to develop business logic. Today, I am not going to discuss how an EJB can be deployed on the server. There are just too many tutorials available on the internet. I will discuss the need to use EJB, where it fits and what it gives. In the recent times, people have preferred Spring framework instead of EJB, the advantage of what is being lightweight. It however needs to be discussed that being lightweight is not the only qualities a business framework needs to have. There is a limit to how much spring can scale. There are also somethings spring simply cannot handle, not at least without external component injected through its AOP framework. Enterprise Java Beans are complex and heavier weight, because they attempt to provide solution to much more complex regime of problems. Also note that, unlike spring, EJB is not a product, its a specification. Which means you would have a choice among many implementations, both proprietary and open source, of EJB; where as there is only one spring.

However, after EJB 3.x, deploying and programming EJBs are easier than doing so with spring... believe me.

Fundamentals of Extensible Business Reporting Language

What is Extensible Business Reporting Language (XBRL): XBRL is an XML based reporting standard mainly designed for financial reporting. However, just like any XML based format, the XBRL standard is open enough to fit into other purposes as well. Most developed countries use XBRL for all financial reporting purposes. There are many documentation about XBRL which are suited to the accounting professionals and business men. However, there is a scarcity of technical documentation. So, I will explain the essential concept of XBRL in this text. Please note that XBRL specification is a very complex specification and it would require more than one article to explain properly. Please stay tuned for more articles.

The following URL will give an idea about how an XBRL document might look in a human readable view http://www.sec.gov/cgi-bin/viewer?action=view&cik=1419793&accession_number=0001144204-11-051027&xbrl_type=v#

Manipulating Java Class Files with BCEL - Part Three: More About BCEL

This is the third article in the BCEL series. You can read all here. Since I have covered the basics, I will accumulate the points left now. I will discuss about local variables, fields, methods and jump instructions.

Manipulating Java Class Files with BCEL - Part Two: Expressions

This is the second article in the series of articles on Apache BCEL. If you have not read part 1, read it here.

Expression Processing: Expressions are key part of a language. In this article, I will discuss how expressions are compiled into java byte code. I will also cover a little bit about compilation process. At the end, I will go through the steps and create a compiler for numerical expression.

Manipulating Java Class Files with BCEL - Part One : Hello World!

What is BCEL: Apache BCEL or Byte Code Engineering Library is a library that enables simpler manipulation of java byte code. Now the question is, why manipulate byte code? There can be a million of reasons. For example, you might want to insert some profiling code in the class file. Or you might want to write your own language that compiles to java byte code. You can also provide some attractive extension to some framework you are creating. Or you can even be more creative than I am and do something that I cannot think of. But for that, you must first understand how java class files work.

Since it is a BCEL tutorial, get the BCEL library first from here

Manipulating java byte code directly is not trivial in nature, so I decided to break the tutorial into a series. This one is the first - the hello world. Keep in touch to learn more.

Java Threads - How They Work

What is Thread: A thread is a single sequence of instructions being executed in a java virtual machine. The instructions in two different threads have no mutual ordering, they can execute independent of each other.

How to create a thread: In java, the only way to create a thread is by creating an object of class java.lang.Thread. In reality, we can either extend the Thread class and override the method run(), or we can implement java.lang.Runnable in a separate class and pass it to Thread's constructor. This article is meant for people who have some experience with Thread programming in java. If you do not know how to do thread programming in java, there is a very good tutorial in here.