Filtering Requests and Responses
A filter is an object that can transform the header and content (or both) of a request or response. Filters differ from Web components in that filters usually do not themselves create a response. Instead, a filter provides functionality that can be “attached” to any kind of Web resource. Consequently, a filter should not have any dependencies on a Web resource for which it is acting as a filter; this way it can be composed with more than one type of Web resource. The main tasks that a filter can perform are as follows:
Query the request and act accordingly.
Block the request-and-response pair from passing any further.
Modify the request headers and data. You do this by providing a customized version of the request. ...
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