Add @RequestAttribute with servlet-based support

Issue: SPR-13894

src/asciidoc/web-mvc.adoc

@@ -1254,6 +1254,7 @@ multiple requests are allowed to access a session concurrently.
   session attributes (e.g. user authentication object) as opposed to model
   attributes temporarily stored in the session as part of a controller workflow
   via `@SessionAttributes`.
+* `@RequestAttribute` annotated parameters for access to request attributes.
 * `HttpEntity<?>` parameters for access to the Servlet request HTTP headers and
   contents. The request stream will be converted to the entity body using
   ++HttpMessageConverter++s. See <<mvc-ann-httpentity>>.
@@ -1794,6 +1795,23 @@ workflow consider using `SessionAttributes` as described in
 <<mvc-ann-sessionattrib>>.
 
 
+[[mvc-ann-requestattrib]]
+==== Using @RequestAttribute to access request attributes
+
+Similar to `@SessionAttribute` the `@RequestAttribute` annotation can be used to
+access pre-existing request attributes created by a filter or interceptor:
+
+[source,java,indent=0]
+[subs="verbatim,quotes"]
+----
+	@RequestMapping("/")
+	public String handle(**@RequestAttribute** Client client) {
+		// ...
+	}
+----
+
+
+
 
 [[mvc-ann-form-urlencoded-data]]
 ==== Working with "application/x-www-form-urlencoded" data

src/asciidoc/whats-new.adoc

@@ -665,6 +665,7 @@ Spring 4.3 also improves the caching abstraction as follows:
 * New `@RestControllerAdvice` annotation with combined `@ControllerAdvice` with `@ResponseBody` semantics.
 * `@ResponseStatus` supported on the class level and inherited on all methods.
 * New `@SessionAttribute` annotation for access to session attributes (see <<mvc-ann-sessionattrib-global, example>>).
+* New `@RequestAttribute` annotation for access to session attributes (see <<mvc-ann-requestattrib, example>>).
 * `AsyncRestTemplate` supports request interception.
 
 === WebSocket Messaging Improvements