As we have seen in the previous section, WCF is an umbrella technology that covers ASMX web services, .NET remoting, WSE, Enterprise Service, and System.Messaging. It is designed to offer a manageable approach to distributed computing, broad interoperability, and direct support for service orientation. WCF supports many styles of distributed application development by providing a layered architecture. At its base, the WCF channel architecture provides asynchronous, untyped message-passing primitives. Built on top of this base are protocol facilities for secure, reliable, transacted data exchange and a broad choice of transport and encoding options.
Let us take an example to see why WCF is a good approach for SOA. Suppose a company is designing a service to get loan information. This service could be used by the internal call center application, an Internet web application, and a third-party Java J2EE application such as a banking system. For interactions with the call center client application, performance is important. For communication with the J2EE-based application however, interoperability becomes the highest goal. The security requirements are also quite different between the local Windows-based application, and the J2EE-based application running on another operating system. Even transactional requirements might vary, with only the internal application being allowed to make transactional requests.
With these complex requirements, it is not easy to build the desired service with any single existing technology. For example, the ASMX technology may serve well for the interoperability, but its performance may not be ideal. The .NET remoting will be a good choice from the performance perspective, but it is not good at interoperability. Enterprise Services could be used for managing object lifetimes and defining distributed transactions, but Enterprise Services supports only a limited set of communication options.
Now with WCF, it is much easier to implement this service. As WCF has unified a broad array of distributed systems capabilities, the get loan service can be built with WCF for all of its application-to-application communication. The following shows how WCF addresses each of these requirements:
- Because WCF can communicate using web service standards, interoperability with other platforms that also support SOAP, such as the leading J2EE-based application servers, is straightforward.
- You can also configure and extend WCF to communicate with web services using messages not based on SOAP, for example, simple XML formats such as RSS.
- Performance is of paramount concern for most businesses. WCF was developed with the goal of being one of the fastest distributed application platforms developed by Microsoft.
- To allow for optimal performance when both parties in a communication are built on WCF, the wire encoding used in this case is an optimized binary version of an XML Information Set. Using this option makes sense for communication with the call center client application, because it is also built on WCF, and performance is an important concern.
- Managing object lifetimes, defining distributed transactions, and other aspects of Enterprise Services, are now provided by WCF. They are available to any WCF-based application, which means that the get loan service can use them with any of the other applications that it communicates with.
- Because it supports a large set of the WS-* specifications, WCF helps to provide reliability, security, and transactions when communicating with any platform that supports these specifications.
- The WCF option for queued messaging, built on Message Queuing, allows applications to use persistent queuing without using another set of application programming interfaces.
The result of this unification is greater functionality, and significantly reduced complexity.