InnerHandler

InnerHandler is a concept often encountered in software development, particularly within the context of HTTP client libraries and message handlers. It represents a component within a chain of handlers that process an HTTP request or response. The term "InnerHandler" specifically refers to a handler that is positioned *before* another handler in the chain, meaning it receives the request or response first and can perform some action before passing it along to the next handler, the "outer" handler.

This pattern is frequently used to implement cross-cutting concerns such as logging, authentication, authorization, caching, or request modification. For example, an authentication handler might be an InnerHandler that adds authentication headers to a request before passing it to another handler responsible for sending the request over the network. Conversely, a response handler might be an InnerHandler that inspects an incoming response for errors before passing it to an outer handler that deserializes the response body.

The InnerHandler pattern allows for a modular and extensible design. Developers can easily add, remove, or reorder handlers in the chain to customize the behavior of an HTTP client without modifying the core logic of each individual handler. This promotes code reusability and simplifies the maintenance of complex request/response processing pipelines. The primary role of an InnerHandler is to execute its specific task and then invoke the `SendAsync` method of its inner handler, effectively delegating the processing to the next stage in the chain.