SOA Web Services - Direct Connection Pattern

Direct Connection Pattern using Single Adapter

This pattern is depicted in the following figure.

The Basic Direct Connection pattern uses a single adapter to connect a service consumer to a service provider. The adapter provides message and data transformation to match the different protocol requirements of the consumer and the provider. This is a very important pattern in the implementation of service-oriented architecture. This is typically used for providing a service-oriented interface to a legacy application. The Rules Repository node shown in the pattern models the service directory. The consumer looks up the directory to discover services and select an appropriate service to use.

Direct Connection using Coupling Adapter

This pattern is depicted in the following figure.

In this case, multiple adapters are coupled to achieve the desired transformation. This improves the adapter reusability in multiple point-to-point connections. The coupled adapters together support the transformation of request and response between the consumer and the provider.

Direct Connection using Service Bus

This pattern is depicted in the following figure.

In this case, we assume that the various Application Server nodes are connected using a common Service Bus. A Source application connects to a desired Target application using this service bus. A source application may connect to more than one target application as depicted in the previous figure. Each connection may use a different connection pattern.

In the pattern diagram, the model adapter connectors and connection rules node are not shown. This is to emphasize the use of the service bus. The service bus minimizes the number of adapters required for each point-to-point connection and is an extension of the Direction Connection with coupling adapter runtime pattern.

Along with the service bus, the adapter connectors may be explicitly modeled as shown in the following figure.

Here, the service bus is said to be of X-type as each of the application services connects to this X-type connector. An example of such an X-type service bus could be an HTTP service bus or a JMS (Java Messaging Service) service bus. The X-type adapter connectors bridge the service consumers and providers of different types to the underlying service bus. The service bus itself may span across multiple tiers, and may even cross enterprise boundaries.

A rules repository node may be added to the above pattern to enable the consumers to search for the services with desired characteristics. Such services may be offered within the enterprise or outside the enterprise. The service bus shown is a subset of the Enterprise Service Bus discussed in Chapter 6.