Previously MediaType could only parse double-quoted parameters without
raising an IllegalArgumentException. Now parameters can also be
single-quoted.

Issue: SPR-8917

HttpStatus cannot be created with an unknown status code. If a server
returns a status code that's not in the HttpStatus enum values, an
IllegalArgumentException is raised. Rather than allowing it to
propagate as such, this change ensures the actual exception raised is
a RestClientException.

Issue: SPR-9406

Default HTTP error exceptions thrown from RestTemplate now include
response headers in addition to the response body. In particular, this
enables inspection of the Content-Type header allowing manual
deserialization of the response body without guessing as to the content
type.

 - introduce HttpStatusCodeException#getResponseHeaders
 - add constructor with headers param for HttpStatusCodeException,
   HttpClientErrorException and HttpServerErrorException
 - preserve exsisting constructor signatures
 - mark HttpHeaders as Serializable
 - generate new serialVersionUID where needed

Issue: SPR-7938

The following style updates have been made in anticipation of
substantive changes in subsequent commits:

 - organize imports
 - correct whitespace errors (leading spaces in code, tabs in Javadoc)
 - wrap Javadoc at 90 chars; make imperative ("Return" vs. "Returns")
 - use conventional constructor argument wrapping

A serialVersionUID has also been added to RestClientException and its
ResourceAccessException subclass for consistency with the rest of that
same exception hierarchy.

Issue: SPR-7938

This commit introduces three abstract WebApplicationInitializers, to be
used in the typical setup of a Spring-based web application.

 - AbstractContextLoaderInitializer provides an abstract base class for
   registering a ContextLoaderListener.

 - AbstractDispatcherServletInitializer provides an abstract base class
   for registering a DispatcherServlet, with an optional root context.

 - AbstractAnnotationConfigDispatcherServletInitializer provides an
   abstract base class for registering a DispatcherServlet and optional
   ContextLoaderListener based on annotated (e.g. @Configuration)
   classes.

Issue: SPR-9300

Reordered inline comments so that they now apply to current
state of the code.

Added logger entry in testlog4j.properties to avoid console
warning.

Issue: SPR-9417

Previously, if the resolution of a ${...} placeholder resulted in a
valid URL for the location of a log4j properties/XML file, the URL
would ultimately be malformed by an unnecessary call to to
WebUtils#getRealPath.

The implementation of Log4jWebConfigurer#initLogging now eagerly
attempts SystemPropertyUtils#resolvePlaceholders before checking to see
if the location is a valid URL, and bypassing the call to
WebUtils#getRealPath if so.

Issue: SPR-9417

SPR-7591 introduced a java.nio.charset.Charset field within
HttpStatusCodeException. The former is non-serializable, thus by
extension the latter also became non-serializable.

Because the Charset field is only used for outputting the charset name
in HttpStatusCodeException#getResponseBodyAsString, it is reasonable to
store the value returned by Charset#name() instead of the actual Charset
object itself.

This commit refactors HttpStatusCodeException's responseCharset field to
be of type String instead of Charset and adds tests to prove that
HttpStatusCodeException objects are once again serializable as expected.

Issue: SPR-9273, SPR-7591

Before this fix the q-value of media types in the Accept header were
ignored when using the new RequestMappingHandlerAdapter in combination
with @ResponseBody and HttpMessageConverters.

Issue: SPR-9160

The ErrorsMethodArgumentResolver expects the preceding @ModelAttribute
in the controller method signature to be the last one added in the
model -- an assumption that can break if a model attribute is added
earlier (e.g. through a @ModelAttribute method) and more attributes
are added as well. This fix ensures when an @ModelAttribute is resolved
as a controller method argument it has the highest index in the model.

Issue: SPR-9378

Jackson serialization supports pretty printing. Usually it's enabled
by invoking ObjectMapper.configure(..), which is not convenient for
apps with XML configuration. The Jackson HttpMessageConverter and View
now both have a prettyPrint property.

A second more serious issue is documented here:
https://github.com/FasterXML/jackson-databind/issues/12

The workaround discussed at the above link has been implemented.

Issue: SPR-7201

Jackson 2 uses completely new package names and new maven artifact ids.
This change adds Jackson 2 as an optional dependency and also provides
MappingJackson2HttpMessageConverter and MappingJackson2JsonView for use
with the new version.

The MVC namespace and the MVC Java config detect and use
MappingJackson2HttpMessageConverter if Jackson 2 is present.
Otherwise if Jackson 1.x is present,
then MappingJacksonHttpMessageConverter is used.

Issue: SPR-9302

The fromUri method of UriComponentsBuilder used uri.getXxx() methods,
which decode the URI parts causing URI parsing issues. The same method
now uses uri.getRawXxx().

Issue: SPR-9317

When a controller returns a DeferredResult, the underlying async
request will eventually time out. Until now the default behavior was
to send a 503 (SERVICE_UNAVAILABLE). However, this is not desirable
in all cases. For example if waiting on an event, a timeout simply
means there is no new information to send.

To handle those cases a DeferredResult now accespts a timeout result
Object in its constructor. If the timeout occurs before the
DeferredResult is set, the timeout result provided to the constructor
is used instead.

Issue: SPR-8617

* Clarify semantics and behavior of AsyncWebRequest methods in most cases
making a best effort and not raising an exception if async processing
has completed for example due to a timeout. The startAsync() method is
still protected with various checks and will raise ISE under a number
of conditions.
* Return 503 (service unavailable) when requests time out.
* Logging improvements.

Issue: SPR-8517

Issue: SPR-8517

From a programming model perspective, @RequestMapping methods now
support two new return value types:

* java.util.concurrent.Callable - used by Spring MVC to obtain the
return value asynchronously in a separate thread managed transparently
by Spring MVC on behalf of the application.
* org.springframework.web.context.request.async.DeferredResult - used
by the application to produce the return value asynchronously in a
separate thread of its own choosing.

The high-level idea is that whatever value a controller normally
returns, it can now provide it asynchronously, through a Callable or
through a DeferredResult, with all remaining processing --
@ResponseBody, view resolution, etc, working just the same but
completed outside the main request thread.

From an SPI perspective, there are several new types:

* AsyncExecutionChain - the central class for managing async request
processing through a sequence of Callable instances each representing
work required to complete request processing asynchronously.
* AsyncWebRequest - provides methods for starting, completing, and
configuring async request processing.
* StandardServletAsyncWebRequest - Servlet 3 based implementation.
* AsyncExecutionChainRunnable - the Runnable used for async request
execution.

All spring-web and spring-webmvc Filter implementations have been
updated to participate in async request execution.
The open-session-in-view Filter and interceptors implementations in
spring-orm will be updated in a separate pull request.

Issue: SPR-8517

Each of these tests began failing during the Gradle build porting
process. None seem severe, many are likely due to classpath issues.

In the case of TestNG support, this needs to be added to the Gradle
build in order to execute these tests. See SPR-8116.txt

This renaming more intuitively expresses the relationship between
subprojects and the JAR artifacts they produce.

Tracking history across these renames is possible, but it requires
use of the --follow flag to `git log`, for example

    $ git log spring-aop/src/main/java/org/springframework/aop/Advisor.java

will show history up until the renaming event, where

    $ git log --follow spring-aop/src/main/java/org/springframework/aop/Advisor.java

will show history for all changes to the file, before and after the
renaming.

See http://chrisbeams.com/git-diff-across-renamed-directories