During my GSoC project for OpenNMS i did some work with JMS and wanted to write test classes to make sure that my code was working well. In this article i will try to explain how you can use ActiveMQ to write test cases for your JMS code. This is very handy when your code has a part that listens to a JMS queue.
Apache ActiveMQ is a extremely popular and very powerful open source messaging and Integration Patterns server. You can check it out here. The part we will be using to run our test classes is the embedded broker that is provided by ActiveMQ. This allows you to create a temporary broker for test purposes to create a JMS queue in our case. If you want to learn more about the embedded broker check out this article. The easiet way to create a embedded broker is through the following code line. This will automatically create a embedded broker. ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("vm://localhost?broker.persistent=false");
In this post we will look into working with binary files in java. The end goal of the post will be to create simple java application that reads a binary file and write it back to a different binary file. The difference between the two files would be the byte order. If we read in a file with Big-endian byte order we will write it back with a Little-endian byte order and vice-versa. Lets first understand what is meant by byte order and what Big-endian and Little-endian are. If you are already familiar with this you can skip this section of the post
Understanding byte order and Endianness
The endianness refers to the order that bytes are stored when storing multi byte values such as Integers and Doubles this is also known as the byte order. The endianness does not have any meaning when you consider a single byte that is stored, and it …
The past few days i grew some interest in Apache Spark and thought of playing around with it a little bit. If you haven't heard about it go an take a look its a pretty cool project it claims to be around 40x faster than Hadoop in some situation. The incredible increase in performance is gained by leveraging in-memory computing technologies. I want go into details about Apache Spark here if you want to get a better look at Spark just check out there web site - Apache Spark.
In this post we will be going through the steps to setup an Apache Spark cluster on your local machine. we will setup one master node and two worker nodes. If you are completely new to Spark i recommend you to go through First Steps with Spark - Screencast #1 it will get you started with spark and tell you how to install Scala and other stuff you need.
We will be using the launch scripts that are provided by Spark to make our lives more easier. First of all there are a couple of configurations we need to set.