In this post, I want to outline two concepts that may help you to create a better service architecture for CA Plex WCF services. First, we should make sure the interfaces are decoupled from the business logic in order to make sure that a change to business functions will not affect the interface used by clients. The second suggestion will make your WCF service more compatible with REST principles and will allow for easier transformation to REST-based services.
Decouple interfaces from business logic
In order to decouple the business logic, we use an adaptor pattern. We create a wrapper function for each method on the interface and define separate input and output parameter fields scoped to the wrapper function.
The following images show a simple example using the “SalesSystem” model shipped with CA Plex. On the IOrder interface, we define a method “GetOrderHeader”. This method is implemented by Function “Order.Header.Adaptor.GetOrderHeader”.
Design for stateless operation
Make sure the exposed methods do not require a session (server application state per client). The standard BlockFetch pattern relies on server state (open cursor).
To get more than one instance from a collection, we still have to hard code the number of instances that will be returned as a page from a service (CA Plex limitation). A PageFetch pattern’s interface has to be designed similar to the one shown below:
Navigation through pages is by PageNumber.
If there are any questions regarding this post please feel free to contact me at lorenz.alder@cmfirstgroup.com.
