Test meta-@Async executor qualification

Prove that Async#value is respected even when using @Async as a meta
annotation.

Issue: SPR-6847
Add convenient WebAppInitializer base classes

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
Merge pull request #62 from poutsma/SPR-9300

* SPR-9300:
  Add convenient WebAppInitializer base classes
Polish scheduled task execution infrastructure

In anticipation of substantive changes required to implement "initial
delay" support in the <task:scheduled> element and @Scheduled
annotation, the following updates have been made to the components and
infrastructure supporting scheduled task execution:

 - Fix code style violations
 - Fix compiler warnings
 - Add Javadoc where missing, update to use {@code} tags, etc.
 - Organize imports to follow conventions
Support initial delay attribute for scheduled tasks

java.util.concurrent's ScheduledExecutorService and its #schedule*
methods allow for an 'initialDelay' parameter in milliseconds.
Similarly, Spring's TaskExecutor abstraction allows for a concrete
'startTime' expressed as a Date. However, Spring's <task:scheduled> XML
element and @Scheduled annotation have, to date, not allowed for an
initial delay parameter that can be propagated down to the underlying
TaskScheduler/ScheduledExecutorService.

This commit introduces initial-delay and #initialDelay attributes to
task:scheduled and @Scheduled respectively, both indicating the number
of milliseconds to wait before the first invocation of the method in
question. Specifying a delay in this fashion is only valid in
conjunction with fixed-rate and fixed-delay tasks (i.e. not with cron
or trigger tasks).

The principal changes required to support these new attributes lie in
ScheduledTaskRegistrar, which previously supported registration of
tasks in the form of a Runnable and a Long parameter indicating (in the
case of fixed-rate and fixed-delay tasks), the interval with which the
task should be executed. In order to accommodate a third (and optional)
'initialDelay' parameter, the IntervalTask class has been added as a
holder for the Runnable to be executed, the interval in which to run
it, and the optional initial delay. For symmetry, a TriggerTask and
CronTask have also been added, the latter subclassing the former. And a
'Task' class has been added as a common ancestor for all the above.

One oddity of the implementation is in the naming of the new
setters in ScheduledTaskRegistrar. Prior to this commit, the setters
were named #setFixedDelayTasks, #setFixedRateTasks, etc, each accepting
a Map<Runnable, long>. In adding new setters for each task type, each
accepting a List<IntervalTask>, List<CronTask> etc, naturally the
approach would be to use method overloading and to introduce methods
of the same name but with differing parameter types. Unfortunately
however, Spring does not support injection against overloaded methods
(due to fundamental limitations of the underlying JDK Introspector).
This is not a problem when working with the ScheduledTaskRegistrar
directly, e.g. from within a @Configuration class that implements
SchedulingConfigurer, but is a problem from the point of view of the
ScheduledTasksBeanDefinitionParser which parses the <task:scheduled>
element - here the ScheduledTaskRegistrar is treated as a Spring bean
and is thus subject to these limitations. The solution to this problem
was simply to avoid overloading altogether, thus the naming of the new
methods ending in "List", e.g. #setFixedDelayTasksList, etc. These
methods exist primarily for use by the BeanDefinitionParser and are
not really intended for use by application developers. The Javadoc for
each of the new methods makes note of this.

Issue: SPR-7022
Merge branch cbeams/SPR-7022

* SPR-7022:
  Support initial delay attribute for scheduled tasks
  Polish scheduled task execution infrastructure
Merge rather than add URI vars to data binding values

As of Spring 3.1 URI variables can be used for data binding purposes in
addition to request parameters (including query string and form params)

In some cases URI variables and request params can overlap (e.g. form
contains a child entity with an entityId as hidden form input while the
URI contains the entityId of the parent entity) and that can lead to
surprises if the application already exists.

This change ensures that request parameters are used first and URI
vars are added only if they don't overlap. Ideally however an
application should not use the same uri variable name as the name of
a request parameter where they don't refer to the same value.

Issue: SPR-9349
Introduce BeanFactoryAnnotationUtils

Commit 096693c46fba6e09b346a498b7002abd4d6540a9 refactored and
deprecated TransactionAspectUtils, moving its #qualifiedBeanOfType
and related methods into BeanFactoryUtils. This created a package cycle
between beans.factory and beans.factory.annotation due to use of the
beans.factory.annotation.Qualifier annotation in these methods.

This commit breaks the package cycle by introducing
beans.factory.annotation.BeanFactoryAnnotationUtils and moving these
@Qualifier-related methods to it. It is intentionally similar in name
and style to the familiar BeanFactoryUtils class for purposes of
discoverability.

There are no backward-compatibilty concerns associated with this change
as the cycle was introduced, caught and now fixed before a release.

Issue: SPR-6847
Fix package cycle in @EnableSpringConfigured

@EnableSpringConfigured and its @Import'ed
SpringConfiguredConfiguration @Configuration class inadvertently
established a package cycle between beans.factory.aspectj and
context.annotation due to SpringConfiguredConfiguration's
dependency on annotations such as @Configuration, @Bean and @Role.

This commit fixes this architecture bug by moving
@EnableSpringConfigured and SpringConfiguredConfiguration from the
beans.factory.aspectj package to the context.annotation package where
they belong.

This change is assumed to be very low impact as @EnableSpringConfigured
was introduced in 3.1.0 and relocation is happening as quickly as
possible in 3.1.2. @EnableSpringConfigured is assumed to be infrequently
used at this point, and for those that are the migration path
is straightforward. When upgrading from Spring 3.1.0 or 3.1.1, update
import statements in any affected @Configuration classes to reflect the
new packaging.

Issue: SPR-9441
Polish

Issue: SPR-9439
Introduce ConfigurableEnvironment#merge

Prior to this change, AbstractApplicationContext#setParent replaced the
child context's Environment with the parent's Environment if available.
This has the negative effect of potentially changing the type of the
child context's Environment, and in any case causes property sources
added directly against the child environment to be ignored. This
situation could easily occur if a WebApplicationContext child had a
non-web ApplicationContext set as its parent. In this case the parent
Environment type would (likely) be StandardEnvironment, while the child
Environment type would (likely) be StandardServletEnvironment. By
directly inheriting the parent environment, critical property sources
such as ServletContextPropertySource are lost entirely.

This commit introduces the concept of merging an environment through
the new ConfigurableEnvironment#merge method. Instead of replacing the
child's environment with the parent's,
AbstractApplicationContext#setParent now merges property sources as
well as active and default profile names from the parent into the
child. In this way, distinct environment objects are maintained with
specific types and property sources preserved. See #merge Javadoc for
additional details.

Issue: SPR-9444, SPR-9439
Introduce ConfigurableWebEnvironment

Changes introduced in Spring 3.1 for Environment support inadvertently
established a cyclic dependency between the
org.springframework.web.context and
org.springframework.web.context.support packages, specifically through
web.context.ContextLoader's invocation of
web.context.support.WebApplicationContextUtils#initServletPropertySources.

This commit introduces ConfigurableWebEnvironment to break this cyclic
dependency. All web.context.ConfigurableWebApplicationContext types now
return web.context.ConfigurableWebEnvironment from their #getEnvironment
methods; web.context.support.StandardServletEnvironment now implements
ConfigurableWebEnvironment and makes the call to
web.context.support.WebApplicationContextUtils#initServletPropertySources
within its implementation of #initPropertySources. This means that
web.context.ContextLoader now invokes
web.context.ConfigurableWebEnvironment#initPropertySources instead of
web.context.support.WebApplicationContextUtils#initServletPropertySources
and thus the cycle is broken.

Issue: SPR-9439
Merge branch cbeams/SPR-9439

* SPR-9439:
  Introduce ConfigurableWebEnvironment
  Introduce ConfigurableEnvironment#merge
  Polish
Support not (!) operator for profile selection

The following syntax is now supported

  <beans profile="p1,!p2">

  @Profile("p1", "!p2")

indicating that the <beans> element or annotated component should
be processed only if profile 'p1' is active or profile 'p2' is not
active.

Issue: SPR-8728
Reduce log level for message re: missing annotation

Previously (since Spring 3.1.1) RecursiveAnnotationAttributesVisitor
logs at level WARN when ASM parsing encounters an annotation or an (enum
used within an annotation) that cannot be classloaded. This is not
necessarily indicative of an error, e.g. JSR-305 annotations such as
@Nonnull may be used only for static analysis purposes, but because
these annotations have runtime retention, they remain present in the
bytecode. Per section 9.6.1.2 of the JLS, "An annotation that is present
in the binary may or may not be available at run-time via the reflective
libraries of the Java platform."

This commit lowers the log level of these messages from warn to debug,
but leaves at warn level other messages dealing with the ability
reflectively read enum values from within annotations.

Issue: SPR-9233
Polish

Issue: SPR-6870
Cache by-type lookups in DefaultListableBeanFactory

Prior to this change, by-type lookups using DLBF#getBeanNamesForType
required traversal of all bean definitions within the bean factory
in order to inspect their bean class for assignability to the target
type. These operations are comparatively expensive and when there are a
large number of beans registered within the container coupled with a
large number of by-type lookups at runtime, the performance impact can
be severe. The test introduced here demonstrates such a scenario clearly.

This performance problem is likely to manifest in large Spring-based
applications using non-singleton beans, particularly request-scoped
beans that may be created and wired many thousands of times per second.

This commit introduces a simple ConcurrentHashMap-based caching strategy
for by-type lookups; container-wide assignability checks happen only
once on the first by-type lookup and are afterwards cached by type
with the values in the map being an array of all bean names assignable
to that type. This means that at runtime when creating and autowiring
non-singleton beans, the cost of by-type lookups is reduced to that of
ConcurrentHashMap#get.

Issue: SPR-6870
Merge branch cbeams/SPR-6870

* SPR-6870:
  Cache by-type lookups in DefaultListableBeanFactory
  Polish
Polish SmartValidator and SpringValidatorAdapter

 - Improve wording & grammar in SmartValidator Javadoc
 - Suppress 'rawtypes' warnings in SpringValidatorAdapter
Handle non-existent files in ServletContextResource

ServletContextResource#getFile now falls back to #getRealPath for
non-existent files

Issue: SPR-8461