Issue: SPR-17356

Issue: SPR-17347

Issue: SPR-17333

Issue: SPR-17332

Issue: SPR-17326

Issue: SPR-17324

Issue: SPR-17323

Issue: SPR-17321

Includes use of Files.getLastModifiedTime for NIO Paths, preservation of NIO-based resolution on createRelative, deprecation of PathResource, and consistent use of getContentLengthLong over getContentLength.

Issue: SPR-17320

Issue: SPR-17267

Replace all method level comments related to forwaded headers, some
current and some outdated, with a single class-level comment.

Issue: SPR-17317

This was a package private class in spring-messaging since 5.0, and was
recently made public in 5.1. This commit promotes it to spring-core
where it belongs next to all other ListenableFuture support classes.

Follow-up refactoring for SPR-17336

Collapse the package private AbstractMonoToListenableFutureAdapter into
its only sub-class MonoToListenableFutureAdapter. There is no need for
such an abstract class that makes it possible to adapt from one source
to a different target type. That's already covered by
ListenableFutureAdapter.

Follow-up refactoring for SPR-17336.

Issue: SPR-17336

Avoid automatically unwrapping the request in TestDispatcherServlet,
if we find the MockAsyncContext.

Issue: SPR-17353

Spring Framework 5.1.0 exposed by mistake context in the Kotlin bean DSL
API in order to fix SPR-16269. Now that BeanFactory#getBeanprovider is
available, it should be exposed via a provider<Foo>() function in order
to provide a more clean API instead.

Issue: SPR-17352

* pr/1983:
  Fix bullet list layout

Closes gh-1983

Explain the need for consistent use of ServerWebExchange for access to
the parsed (and cached) form data or multipart data.

Issue: SPR-17291

Headings are optimized for how they appear in the left-hand side
navitation menu, with context provided by parent headings, and not
necessarily for how they read on their own.

At 2nd and 3rd level of nesting, which is where most headings are,
the wrapping becomes too distracting and the left-hand side navigation
sprawling.

Issue: SPR-17284

Issue: SPR-17345

Issue: SPR-17338

Previously, both nullsLow(Comparator<T>) and
nullsHigh(Comparator<T>) returned a
NullSafeComparator which treated nulls as being
high. This commit corrects this typo.

* pr/1979:
  Fix formatting

Prefix the opening brace with a single space in some classes.
Replace tab character with space in javadoc of AttributeAccessor.
Also fix some other trivial formatting errors.

Closes gh-1979

With this commit, we now make sure that the attributes are not cleared
if they are same as the nested request.

Issue: SPR-17304

This commit adds test for delegating request predicates that verify
whether the request attributes are properly restored when a delegate
fails.

In order to be able to leverage WebFlux configuration in a functional
way, WebHttpHandlerBuilder and RouterFunctionMapping should leverage
new ObjectProvider capabilities to get a sorted list of beans by type
instead of using autowired containers.

Issue: SPR-17327

Switch to using the sendClose method available since Reactor Netty 0.8
vs explicitly sending a CloseWebSocketFrame.

Related to SPR-17306, but does not address the root cause.

Issue: SPR-17321, #1974

Issue: SPR-17321, #1974

Issue: SPR-17321, #1974