Chapter 10. Web services scenario 293
The Processor application uses this proxy to call the HomeDelivery Web
service. The ESB intercepts the request and routes it to the appropriate
Enterprise service bus (ESB)
The ESB is implemented using the service integration bus. The bus acts as
an intermediary for the Web service. Using an ESB insulates the application
from changes in the Web service location and provides the opportunity to
implement mediations or security measures in the future.
The CreditCheck Web service returns a credit rating for the customer.
The DeliverySystem application has two Web services: HomeDelivery and
BusinessDelivery. These delivery systems create account numbers for the
new customer and return the information to the user.
This scenario illustrates the following three application patterns using Web
Directly Integrated Single Channel application pattern:
ITSOMart calls a Web service that returns a customer credit rating. The rating
is used to determine whether to allow the customer to open an account.
Router application pattern
ITSOMart allows the user to select whether they want home delivery,
business delivery, or both. If home or business delivery is chosen the request
is routed to the appropriate service to assign an account number that is then
returned to the user. The routing is performed through the use of a mediation
in the ESB.
Decomposition application pattern
If the user selects both home delivery and business delivery, the request for
an account number is sent to both services. The responses with the account
numbers are aggregated into a single response for the customer. The
decomposition of the message into multiple messages and the recomposition
into a single response are performed through the use of a mediation in the