anchor.diff:  the way they are used is very different. Spring MVC relies on Servlet blocking I/O and
   lets applications use the Servlet API directly if they need to. Spring WebFlux
   relies on Servlet 3.1 non-blocking I/O and uses the Servlet API behind a low-level
  -adapter and not exposed for direct use.
  +adapter. It is not exposed for direct use.
   
   For Undertow, Spring WebFlux uses Undertow APIs directly without the Servlet API.
   
  
positive.code: === `HttpHandler`
  
  {api-spring-framework}/http/server/reactive/HttpHandler.html[HttpHandler]
  is a simple contract with a single method to handle a request and response. It is
  intentionally minimal, and its main, and only purpose is to be a minimal abstraction
  over different HTTP server APIs.
  
  The following table describes the supported server APIs:
  
negative.code: the `ObjectMapper` as soon as enough bytes are received for a fully formed object. The
  input content can be a JSON array, or
  https://en.wikipedia.org/wiki/JSON_streaming[line-delimited JSON] if the content-type is
  `application/stream+json`.
  
  The `Jackson2Encoder` works as follows:
  
  * For a single value publisher (e.g. `Mono`), simply serialize it through the
  `ObjectMapper`.
  * For a multi-value publisher with `application/json`, by default collect the values with
  `Flux#collectToList()` and then serialize the resulting collection.
  * For a multi-value publisher with a streaming media type such as
  `application/stream+json` or `application/stream+x-jackson-smile`, encode, write, and
  