Since Spring Framework 2.5, @Rollback has been supported on test
methods, with class-level rollback settings configured via
@TransactionConfiguration; however, allowing @Rollback to be declared
on test classes with method-level declarations overriding class-level
declarations would prove more intuitive than having to declare both
@TransactionConfiguration and @Rollback. Furthermore, the
transactionManager flag in @TransactionConfiguration was made
superfluous many years ago with the introduction of support for a
qualifier in @Transactional.

This commit enables @Rollback to be declared at the class level for
default rollback semantics within test class hierarchies and deprecates
@TransactionConfiguration in favor of @Rollback and @Transactional
qualifiers.

Issue: SPR-13276, SPR-13277

Issue: SPR-13272

AbstractMessageConverter provides overloaded methods with a conversion hint, MappingJackson2MessageConverter takes that hint into account, and SimpMessagingTemplate transformes such a hint in the given headers map into an explicit argument invocation argument.

Issue: SPR-13265

Prior to this change, calling the `setDateHeader` method on a
Spring Test MockHttpServletResponse instance would just store the given
long value in a Map, not writing it as a formatted date String.
Also, calling `getDateHeader` on a MockHttpServletRequest would not
support date strings and could not parse those values.

This can be problematic when testing features related to date headers
such as "Expires", "If-Modified-Since", "Last-Modified", etc.

This commit adds formatting and parsing capabilities to Servlet Mocks
for date strings in HTTP headers.

When formatting dates to Strings, the date format used is the one
preferred by the HTTP RFC. When parsing date Strings, multiple date
formats are supported for better compatibility.

Issue: SPR-11912

SPR-13211 introduced support for reusing mock requests in Spring MVC
Test if the request was created by the the Spring TestContext
Framework. Unfortunately, that change makes it impossible for
MockMvc.perform() to be invoked multiple times within the same test
method without side effects. For example, session attributes and
request parameters are transparently and unexpectedly retained for
subsequent invocations of perform(), causing certain categories of
tests to fail.

This commit reverts the changes introduced in SPR-13211 and introduces
a new MockMvcReuseTests class to serve as regression tests within
Spring's test suite.

Issue: SPR-13260, SPR-13211

Issue: SPR-13257

HTTP headers such as "Expires", "Last-Modified" all use date
strings like "Tue, 21 Jul 2015 10:00:00 GMT". Prior to this commit,
there was no way to match those header values, besides formatting dates
manually.

This commit introduces a new HeaderResultMatcher to test those date
headers using a long timestamp:

```
this.mockMvc.perform(get("/persons/1").header("If-Modified-Since", now))
  .andExpect(status().isNotModified())
  .andExpect(header().dateValue("Last-Modified", timestamp));
```

Issue: SPR-13263

Streamlined WebContentGenerator API variants: checkRequest, prepareResponse, applyCacheControl, applyCacheSeconds

Issue: SPR-11792

Issue: SPR-13006

Prior to this change, calling the `setDateHeader` method on a
MockHttpServletResponse instance (internal implementation for testing
the spring-web module) would just store the given long value in a Map,
not writing it as a formatted date String.

This can be problematic when testing features related to date headers
such as "Expires", "If-Modified-Since", "Last-Modified", etc.

This commit formats long dates into date Strings using the date format
recommended by the RFC and the GMT time zone.

As filter-based libraries and projects (such as Spring Security) may
use the "Pragma" header in HTTP responses, WebContentGenerator should
make sure that such headers are overwritten to avoid clashes with
the HTTP caching headers set by the HTTP caching configuration.

Issue: SPR-13252

Use ServletHttpResponse.setDateHeader whenever possible and avoid using
SimpleDateFormat.

Prior to this commit, the Spring MVC Test Framework always created a
new MockHttpServletRequest, disregarding any mock request already
present in Spring Web's RequestContextHolder -- for example, one
created by the ServletTestExecutionListener in the Spring TestContext
Framework (TCF).

This commit modifies MockHttpServletRequestBuilder so that it reuses a
mock request created by the TCF. However,
MockMultipartHttpServletRequestBuilder continues to always create a new
MockMultipartHttpServletRequest since a MockHttpServletRequest created
by the TCF is not directly compatible with a
MockMultipartHttpServletRequest. Furthermore, in order to avoid
unforeseen side effects, MockHttpServletRequestBuilder will always
create a new MockHttpServletRequest if a mock request is present in the
RequestContextHolder but not created by the TCF.

Issue: SPR-13211

This commit replaces calls to System.out.println() with explicit logging.