Latest dependency updates (Tomcat 9.0.27, Undertow 2.0.27, RxJava 2.2.13, Gson 2.8.6, Apache Johnzon 1.2.1, Hibernate ORM 5.4.8, EclipseLink 2.7.5, H2 1.4.200, POI 4.1.1, Quartz 2.3.2, WebJars Locator 0.42, HtmlUnit 2.36, Checkstyle 8.26, Mockito 3.1, Objenesis 3.1)

Closes gh-23871

Closes gh-23870

See gh-23871

See gh-23870

Make use of the new getAvailableExtensionNames() method.

Closes gh-23799

Make use of the new getAvailableExtensionNames() method.

Closes gh-23565

See gh-23698

Closes gh-23698

Closes gh-23662

Upgrade to Aalto 1.2.2, Protobuf 3.10, Apache Johnzon 1.2, SnakeYAML 1.25, OpenPDF 1.3.11, FreeMarker 2.3.29

Upgrade to SLF4J 1.7.28, Groovy 2.5.8, RxJava 2.2.12, Joda-Time 2.10.4, Rome 1.12.2, OkHttp 3.14.3, Apache HttpClient 4.5.10, Apache Johnzon 1.1.13

Closes gh-23663

Closes gh-23703

This commit adds the following exclusions to the source of the
checkstyleNoHttp tasks for each project in the build and for buildSrc:

- bin/ directory (created by Eclipse Buildship)
- .settings directory (created by Eclipse)
- .classpath file (created by Eclipse)
- .project file (created by Eclipse)

An exclusion for the build/ directory is also configured as the
NoHttp plugin does not exclude it by default for buildSrc.

Closes gh-23702

RSocket is still in its RC phase, but those artifacts are published on
maven central. This dependency is currently still depending on a
milestone dependency for Reactor adn this is causing issues with our
build.

This commits adds back the milestone repository until the RSocket POMs
and BOMs are fixed. Once fixed, the Framework build should use the
RSocket BOM for managing RSocket dependencies.

See gh-23698

Includes Netty 4.1.39 (aligned with Reactor) and Checkstyle 8.24.

Closes gh-23695

Closes gh-23694

Closes gh-23690

This commit makes sure we narrow down dependencies of the Spring
Framework to only Maven central. Optional dependencies that are not
available on Maven Central are now served from a more specific
repository (`libs-spring-framework-build`).

Closes gh-23124

Prior to this commit, Spring Framework would use `Schedulers.elastic()`
in places where we needed to process blocking tasks in a reactive
environment.

With reactor/reactor-core#1804, a new `Schedulers.boundedElastic()`
scheduler is available and achieves the same goal with added security;
it guarantees that resources are bounded.

This commit uses that new scheduler in the standard websocket client,
since the underlying API is blocking for the connection phase and we
need to schedule that off a web server thread.

Closes gh-23661
See gh-23665

Closes gh-23619

Previously, changing modules (snapshots) and dynamic versions were
cached for Gradle's default period of 24 hours and
--refresh-dependencies was used to pick up the latest artifacts. This
approach has a notable downside. --refresh-dependencies causes all
dependencies to be refreshed, irrespective of whether they are
expected to change. At a minimum, this results in a HEAD request for
every dependency in the build. Running an up-to-date build without
--refresh-dependencies takes in the region of 6 seconds:

$ ./gradlew build

BUILD SUCCESSFUL in 6s
203 actionable tasks: 203 up-to-date

The same build with --refresh-dependencies takes almost ten times as
long:

$ ./gradlew build --refresh-dependencies

BUILD SUCCESSFUL in 58s
203 actionable tasks: 203 up-to-date

This commit replaces the manual usage of --refresh-dependencies on
the command line with a 0 second caching period for changing modules
and dynamic versions. This should remove the need to use
--refresh-dependencies both locally and on CI, saving almost 1 minute
per full build.

This commit also removes the testRuntime dependency on Hamcrest which
was a workaround for https://github.com/junit-team/junit5/issues/2004.

Closes gh-23604

Since it does not appear that JUnit 4.13 will be released before Spring
Framework 5.2 GA, I am reverting back to JUnit 4.12 for the time being.

See gh-22894

See gh-23604

This commit adds opt-in build scan integration with Gradle Enterprise.
When the GRADLE_ENTERPRISE_URL environment variable is set on a
developer's machine or on CI, a build scan will be automatically
uploaded to Gradle Enterprise at the end of the build.

This initial integration will establish a baseline for Spring
Framework builds. Once that baseline has been established we can use
the build scans to identify ways in which the build can be optimized
and updated to make use of Gradle's build caching which should reduce
build times, significantly so for changes that only affect tasks near
the leaf nodes of the task graph.

See also: 69214429 and eec183ef

The upgrade to 4.x was breaking some behavior in our tests.
We need to reconsider this upgrade and check our mockrestserver usage in
our tests.

This commit reverts all artifactory configuration changes in this
branch. A new build plan has been created for the master branch which is
tailored for the latest Gradle changes made on that branch.

Closes: gh-23579

Prior to this commit, tests in spring-web and spring-webflux were no
longer executed due to the removal of the Hamcrest dependency in
commit bb03cdf5.