- Integrating systems and applications together
- Get software systems to work in perfect synchronism with each other
- Not limited to integration within an organization
- Integrating with customer applications
- Integrating with supplier/partner applications
- Integrating with public services
By using EAI, we have got another problem that how can we talk to each different services which develop on different technologies, different languages, different protocols, different platforms, different message formats and different QoS requirements (security, reliability). ESB is the rescue for this problem.
Now we will see how can we use ESB to resolve this problem. Think a real scenario. A Chinese girl is joining who does not know English in your classroom. Think you know only Englis and you don't know Chinese. So how can you communicate with that Chinese girl? In this scenario, you can a friend who knows Chinese and English. Through that, you can easily communicate with that girl. This is cost and time effective as you don't need to study Chinese.
Now we can apply this solution to the software industry. Let's assume, you are developing a business application for buying a dress. There you need to talk to Sales System, Customer System, and Inventory system. In this example, let's assume sales system built using SOAP protocol (Exposing SOAP services). Customer system using XML based REST services and Inventory system using JSON-based REST services. Now you need to deal with multiple protocols. Here we can use ESB as the rescue.
What is ESB?
The normal bus is used to transfer from one place to another place. In ESB, you need to pass your message to ESB, ESB will pass your message to a destination. Also if destination sends a response, ESB will take that response and deliver to you. In the previous example, sales system will send the soap message to ESB. ESB will take this message and convert it to XML based REST message to the cusomer system. You may connect to multiple application through ESB. But you only need to do one simple connection which calls ESB only. ESB will talk to rest of the applications.