Business Use Case For the Basic Example

The purpose of an Enterprise Service Bus (ESB), also known as a Java Business Integration (JBI) bus, is to provide a mechanism for different applications to exchange messages in a protocol neutral manner and provide services for processing those messages such as message transformation and dynamic routing. ServiceMix is an implemenation of JSR 208, the JBI specification.

The Basic example demonstrates how external ¹ applications communicate via the ESB. Similar techniques could be used to plug any external application or service into ServiceMix (e.g. SAP, Peoplesoft, spreadsheets, POJOs, Webservices and EJBs) and allow it to communicate with other external applications or components within ServiceMix itself.

Please note: There is one caveat with the Basic example: it uses inbound messages via the resource adapter ² and most legacy ³ applications won't support inbound messaging via the resource adapter.

A common business scenario, which extends the Basic Example, is that of a large department store distributor. This distributor sells products from many wholesalers to many retail outlets (i.e., department stores). The distributor presents a common interface for product ordering to each of its department store customers. However, each wholesaler presents a different ordering interface to the distributor for the product the wholesaler supplies.

Using an ESB, the distributor has developed a number of components to receive department store orders and dynamically route and transform these orders to the appropriate wholesaler. The order flow is described as follows:

1. Using the distributor's web interface, a department store buyer submits an order for multiple products. An HTTP request is sent to the "OrderReceiver, an HTTP binding component (BC). ⁴
2. The OrderReceiver sends the message to an "OrderRouter" Service Engine (SE) ⁵ component. This SE is responsible for parsing the order and deciding, based on the message content, which OrderTransformer should receive the message.
3. The OrderRouter publishes the order to the appropriate JMS topic. It decides which topic to publish to based on message content. Specifically, the OrderRouter publishes the messages based on which wholesaler sells the item.
4. The OrderTransformer is a Service Engine component, which modifies the message and puts it in a format which is readable by the wholesaler interface that will fullfill the order.
5. Each OrderTransformer sends the modified message to the OrderProcessor.
6. The OrderProcessor is a Binding Component that has two functions. The OrderProcessor places an order to the appropriate wholesaler through the wholesaler's Webservice or propriety interface.
7. The OrderProcessor also publishes a message about the order on a topic.
8. The message on the topic is subsequently picked up by the BusinessMonitor component. This component monitors the orders for quality assurance.

The following diagram illustrates this:

1. External means the application is outside of the enterprise service bus.
2. Resource Adapter: a resource adapter provides connectivity between a specific external application and the ESB. In the Basic example, the resource adapter is an ActiveMQ adapter supplied by the jencks JCA Container.
3. Legacy Application: a legacy application does not have a Java API or export data in a non-proprietary format such as XML. Examples of proprietary applications are Peoplesoft, SAP, various spreadsheets, etc.
4. Binding Component (BC): a BC provides connectivity to applications that are external to the ESB.
5. Service Engine (SE): a service engine provides business logic and transformation services to other components within the enterprise service bus.

Related Documentation

JSR 208,