XBus Enterprise Application Integration

Here's my primer on XBus which is an open source Enterprise Application Integration framework available on sourceforge.

What is it?

It's a framework (set of tools) which allows data (text, xml, byte streams) to be translated, processed, and routed from one system to another (database, AS400, Web Service) using a variety of protocols (HTTP, File, JDBC, FTP).

Can you give me an example?

Let's say you need to go to a FTP site and download a bunch of account numbers and dump it into a database everyday. You could hire a programmer to write a program to do it. He would choose his favorite language (probably a scripting language like ruby or perl) then create a cron job to run the script. It would take him 1 day to do it. His code would not be very maintainable except by himself.

With xBus, and armed with some xml parsing and transformation tools, you could create an xBus system by defining routing rules in several config file. It would take you half a day to do it and it would be very maintainable - involving no new code.

Are you kidding me?

Maybe.

Break it down for me

You have config files which are named standard_whatever.conf. It has to start with standard and it has to end with .conf. Inside the config file you have your base definitions. This includes the setup for Trace (logging), Journaling (more logging), Error Handling (Error logging) and other system parameters. You can have more config files, which are also read and appended to each other. Just make sure you don't define the same thing twice. Each entry in the config file contains a key and value. Each key is categorized by three parts - namely chapter, section and key.

To create a process you need to some systems. All systems get data from someplace such as files, HTTP connections, FTP or other systems). If the system gets data from an external source, its called a receiver. Some systems sends data somewhere else. If the system sends data to an external sink, its called a sender. So the most basic process is one receiver, one sender and one routing instruction.

To define a system, several configuration entries are needed, according to the type of system. For example for a FileReceiver, you need to define the filename, the type of message and what to do with the file if there is an error, if the file is empty, etc.

To define a routing instruction (which is sequential in nature) You need to define the routing strategy. This can be either Invoke, Distribute or both. With Invoke, the message is sent and the response and acknowledgment is required. With Distribute only the acknowledgment is required.

How do you run a process

There are two ways to run a process. The first is to run it manually. A simple command is issued from the console. It can be linked to a scheduled task/cron job. The second way, which is required for certain Receivers is to add it to a servlet engine or a background service. This is required if you're polling a folder, or listening to a socket, or accepting HTTP requests. So they way to run your process depends on what your first system is.

Is that all?

No. There's more. But this is a primer, not a user's guide. There's lots more but this should help you wrap your head around the concepts. There are other features such as XSL transformations, Java Message Queues for asynchronous processing, Tomcat integration etc. Good luck.