Why Enterprise Integration?
Beginning on the 90's, having a computer information system is a must for any company; even small drugstores have their own information system; also, starting from the 2000's, having a website is a must for most companies. Nowadays there are lots of online businesses and companies who own a huge ecosystem of applications, websites and third party systems.In this scenario, one thing naturally emerged: information and business processes is fragmented!
Building a completely new application to mitigate this fragmentation is not practical on most cases so, what should a company do?
The answer is quite simple, something there must be on the middle whether people or software and there is where enterprise integration comes into play.
There is on the Java world also a number of enterprise middleware vendors, some are Mule ESB and Apache Camel and today I'll try to demonstrate how to use the first one which is the one I know better.
Mule ESB
Mule is an open source enterprise service bus which aims to be powerful and simple at the same time. It is very configurable and rather complex integrations can be achieved in a matter of hours.
In order to use Mule ESB, the developer has two main options: It can be used as an application container (with deployment based on archives) or embedded inside a java application.
Every Mule ESB application consists of an XML file which combines a number of built-in building blocks to perform a specific integration task, this task has the name of "flow".
Mule also provides some visual tooling, an IDE based on Eclipse, called "Mule Studio" which greatly helps the developer, to create, package and deploy Mule applications, specially it has visual tooling to create interfaces making the learning curve really flat.
A Sample Mule Application
In order to explain further, let's take a look at a simple Mule Application, this application takes requests from http, logs some information, sends information through JMS and inserts records into a database. Any java developer knows that this task may take a couple of hours, but with Mule, this can be done in a matter of minutes. Here is how this application looks in Mule Studio:
Here we have defined a flow (integration), an application may have many flows; the first building block is an HTTP endpoint (called http inbound endpoint) and through the arrows travels a message (actually an instance of MuleMessage). This message contains headers and a payload (also other things such as attachments and other information), with each building block we'll be manipulating or extracting information from it.
I'll not cover in depth the concept of the message but is enough to say that this concept is key for understanding the tool. As an example, imagine a HTTP request, it has headers and a request body, the inbound endpoint will create a mule message with these request headers as the message headers and the request body as the payload. Now, for example, to send the message through JMS, the JMS outbound endpoint would create a JMS message with the Mule message headers as headers and the payload as the JMS payload.
The sample application looks on it's XML form like the following:
The first thing to note is the presence of connectors, these can be seen as a global configuration elements for each transport (in this case JMS and JDBC).
Next we can see the definition of the flow in which we just log the message; set the payload to be a hash map created out of the request query string; send this to an ActiveMQ broker; insert an audit record and finally build a generic JSON response, as you can see a lot is going on for so few configuration lines!
Mule ESB provides out of the box support for several transports such as HTTP, FTP, SMTP, IMAP, SOAP, REST, JMS, JDBC, etc and also ready-to-go clients (called cloud connectors) for popular cloud applications such as Facebook, Twitter, Salesforce and many more.
This completes this short introduction of this tool which is definitely worth looking into when it comes the time for integrating two or more applications.
Next we can see the definition of the flow in which we just log the message; set the payload to be a hash map created out of the request query string; send this to an ActiveMQ broker; insert an audit record and finally build a generic JSON response, as you can see a lot is going on for so few configuration lines!
Mule ESB provides out of the box support for several transports such as HTTP, FTP, SMTP, IMAP, SOAP, REST, JMS, JDBC, etc and also ready-to-go clients (called cloud connectors) for popular cloud applications such as Facebook, Twitter, Salesforce and many more.
This completes this short introduction of this tool which is definitely worth looking into when it comes the time for integrating two or more applications.
