Issue: SPR-11393

Prior to this commit, there existed several isEmpty() methods scattered
across various utilities such as ObjectUtils, CollectionUtils, and
StringUtils; however, each of these methods requires a cast to the type
supported for that particular variant.

This commit introduces a general-purpose isEmpty(Object) method in
ObjectUtils that transparently supports multiple object types in a
central location without the need for casts or juggling multiple
utility classes.

Issue: SPR-13119

The modifications to DefaultMockMvcBuilder performed in conjunction
with SPR-12553 introduced a breaking change: the WebApplicationContext
supplied to DefaultMockMvcBuilder's constructor was *always* stored in
the ServletContext as the root WebApplicationContext, overwriting a
root WebApplicationContext that had been set by the user or by the
Spring TestContext Framework (TCF) -- for example, in
AbstractGenericWebContextLoader. Consequently, the changes in SPR-12553
cause tests that use @ContextHierarchy to fail if web components rely
on the correct WebApplicationContext being stored under the
WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE key.

This commit reverts the breaking changes introduced in SPR-12553: if
the root WebApplicationContext has already been set in the
ServletContext of the WebApplicationContext supplied to
DefaultMockMvcBuilder, no action is taken.

Furthermore, this commit introduces new code to address the initial
intent of SPR-12553. Specifically, if the root WebApplicationContext
has NOT been set in the ServletContext of the WebApplicationContext
supplied to DefaultMockMvcBuilder, the application context hierarchy
will be traversed in search of the root WebApplicationContext, and the
root WebApplicationContext will then be stored under the
ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE key.

Issue: SPR-13075, SPR-12553

Prior to this change, the `"Last-Modified"` and "`Etag`" support had
been improved with SPR-11324: HTTP response headers are now
automatically added for conditional requests and more.

This commit fixes the format of the "`Last-Modified`" and "`ETag`"
values, which were using an epoch timestamp rather than an HTTP-date
format defined in RFC 7231 section 7.1.1.1.

Also, Conditional responses are only applied when the given response
applies, i.e. when it has an compatible HTTP status (2xx).

Issue: SPR-13090

Issue: SPR-13102

Issue: SPR-13112

Issue: SPR-13108

Issue: SPR-13101

Issue: SPR-13104

This commit introduces support for RFC 7239: Forwarded HTTP Extension in
the UriComponentsBuilder. Unfortunately, RFC 7239 is not a complete
replacement for the X-Forwarded-* headers: specifically, there is not
direct replacement for X-Forwarded-Port. The JIRA contains more
information.

Issue: SPR-11856

Issue: SPR-11807

Provide a mean to detect the actual ResolvableType based on a instance as
a counter measure to type erasure.

Upgrade the event infrastructure to detect if the event (or the payload)
implements such interface. When this is the case, the return value of
`getResolvableType` is used to validate its generic type against the
method signature of the listener.

Issue: SPR-13069

Issue: SPR-13103

This commit introduces the following changes:
 - configureCors(CorsConfigurer configurer) is renamed to
   addCorsMappings(CorsRegistry registry)
 - enableCors(String... pathPatterns) is renamed to
   addMapping(String pathPattern)
 - <cors /> element must have at least one <mapping /> child
   element in order to be consistent with XML based configuration
   and have more explicit configuration

Issues: SPR-12933, SPR-13046

While working on SPR-12532, an extra IdentityWrapper was added to work
around a backward compatible issue between commons pool 1.x and 2.x. This
issue (POOL-283) has actually been fixed in 2.4 and their IdentityWrapper
is using object equality so our wrapper is in the way.

Looking retrospectively, the code looks all fine without the workaround
and commons pool 2.4 or later so it has been removed.

Issue: SPR-13097

Also removes "throws Exception" declaration from ThreadPoolExecutorFactoryBean's getObject method.

Issue: SPR-13095

Issue: SPR-13076

Issue: SPR-11393

Issue: SPR-11393

Issue: SPR-13091

Issue: SPR-11393

Issue: SPR-11393

Since Spring 4.1, a CacheResolver may be configured to customize the way
the cache(s) to use for a given cache operation are retrieved. Since a
CacheResolver implementation may not use the cache names information at
all, this attribute has been made optional.

However, a fix was still applied, preventing a Cache operation without a
cache name to be defined properly. We now allow this valid use case.

Issue: SPR-13081

Issue: SPR-13071

This commit introduces support for this kind of CORS XML namespace configuration:

	<mvc:cors>

		<mvc:mapping path="/api/**"
					allowed-origins="http://domain1.com, http://domain2.com"
					allowed-methods="GET, PUT"
					allowed-headers="header1, header2, header3"
					exposed-headers="header1, header2" allow-credentials="false"
					max-age="123" />

		<mvc:mapping path="/resources/**" allowed-origins="http://domain1.com" />

	</mvc:cors>

Issue: SPR-13046

Issue: SPR-13091

Issue: SPR-13089

Includes other recent dependency updates (JRuby 1.7.20, Jetty 9.2.11, Tomcat 8.0.23, Reactor 2.0.3)

Issue: SPR-13088