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Designing a Service's Interaction Layer

  Delegating to existing business logic

  Handling errors

It is generally advisable to do all common processing such as security

checks, logging, auditing, input validation, and so forth for requests at the inter 

action layer as soon as a request is received and before passing it to the processing

layer.

3.4.3 Delegating Web Service Requests to Processing Layer

After designing the request preprocessing tasks, the next step is to design how to

delegate the request to the processing layer. At this point, consider the kind of pro 

cessing the request requires, since this helps you decide how to delegate the request

to the processing layer. All requests can be categorized into two large categories

based on the time it takes to process the request, namely:

  A request that is processed in a short enough time so that a client can afford to 

block and wait to receive the response before proceeding further. In other 

words, the client and the service interact in a synchronous manner such that the 

invoking client blocks until the request is processed completely and the re 

sponse is received.

  A request that takes a long time to be processed, so much so that it is not a good 

idea to make the client wait until the processing is completed. In other words, 

the client and the service interact in an asynchronous manner such that the in 

voking client need not block and wait until the request is processed completely.

Note:

 When referring to request processing, we use the terms synchronous

and asynchronous from the point of view of when the client's request processing

completes fully. Keep in mind that, under the hood, an asynchronous interaction

between a client and a service might result in a synchronous invocation over the

network, since HTTP is by its nature synchronous. Similarly, SOAP messages

sent over HTTP are also synchronous.