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. The 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.

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). ²
2. The OrderReceiver sends the message to an "OrderRouter" Service Engine (SE) ³ component. This SE is responsible for parsing the order and deciding, based on the message content, which OrderTransformer should receive the message.
3. 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.
4. Each OrderTransformer sends the modified message to the OrderProcessor.
5. The OrderProcessor is a Binding Component that has two functions. First it publishes a message about the order on a topic, which is subsequently picked up by the BusinessMonitor component. The OrderProcessor also places an order to the appropriate wholesaler through the wholesaler's Webservice or propriety interface.

The following diagram illustrates this:

In comparison, the Basic example, looks like the following diagram. This is a simplified diagram of the basic example. For a complete diagram, please see: Basic Example.

Please note: The Basic example uses inbound messages via the resource adapter, and most legacy applications won't support inbound messaging via the resource adapter.

1. External means the application is outside of the enterprise service bus.
2. Binding Component (BC): a BC provides connectivity to applications that are external to the ESB.
3. Service Engine (SE): a service engine provides business logic and transformation services to other components within the enterprise service bus.
4. Resource Adapter: a resource adapter provides connectivity between a specific external application and the ESB.