Using Layered Application

The secret to creating an easy-to-use infrastructure for distributed systems is Layered Application. A distributed services layer relies on lower layers, such as the TCP/IP stacks and socket communication layers, but hides the details of these layers from upper layers that contain the application and business logic layers. This arrangement allows the application developer to work at a higher level of abstraction without having to worry about such details as TCP/IP packets and network byte ordering. It also allows lower layers to be replaced without any impact on the upper layers. For example, you can switch to a different transport protocol (for example HTTP instead of straight TCP/IP) without changing code at the application layer.

One way to make remote invocation easy for developers is to use a Proxy [Gamma95]. A proxy is a local stand-in object with which the client object communicates. When the client creates an instance of the remote object, the infrastructure creates a proxy object that looks to the client exactly like the remote type. When the client invokes a method on that proxy object, the proxy invokes the remoting infrastructure. The remoting infrastructure routes the request to the server process, invokes the server object, and returns the result to the client proxy, which passes the result to the client object. Because all of this happens behind the scenes, the client object may be completely unaware that the other object resides on a different computer. This not only makes developing distributed applications easier, it also allows you to distribute objects after the program has been developed while only minimally changing the application code.

Enterprise Solution Patterns Using Microsoft. NET 2003
Enterprise Solution Patterns Using Microsoft. NET 2003
Year: 2004
Pages: 107 © 2008-2017.
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