See gh-2396

Closes gh-2396

This commit adds support for configuring Log4j 2 with YAML. It also
improves the existing support for configuring Log4j 2 with JSON.

Previously, Log4J2LoggingSystem returned a hard-coded list of standard
config locations that includes both JSON and XML file suffixes. Log4j 
2’s support for JSON configuration files requires Jackson’s ObjectMapper
to be on the classpath so, in its absence, the standard config locations
were incorrect.

This commit updates Log4J2LoggingSystem to return an array of standard
config locations based on what’s on the classpath. It also updates the
documentation to describe the additional dependencies that are required
to enable YAML or JSON-based configuration.

Closes gh-2239

Closes gh-2394

At the time of writing WAS only supports JPA 2.0 which means that
Hibernate 4.2 is the latest version that can be used. SpringJtaPlatform
is Hibernate 4.3-specific as JtaPlatform’s package changed between
Hibernate 4.2 and 4.3. This means that SpringJtaPlatform can’t be used
on current versions of WAS. Futhermore, SpringJtaPlatform won’t work on
WAS even if we could use Hibernate 4.3 as WAS doesn’t make its
TransactionManager available to application code (it’s considered too
dangerous for general consumption) and SpringJtaPlatform
requires a TransactionManager.

This commit updates HibernateJpaAutoConfiguration to always treat WAS as
a special case and configure Hibernate with one of its WAS-specific
JtaPlatform implementations. 

Closes gh-2326

By default, when building a project's jar its runtime dependencies
are not taken into account as they are not needed to successfully
compile the code that will be packaged in the jar. A side-effect of
this was that, if a project that was being repackaged had a runtime
dependency on another project, then the repackaged jar would not
include the jar of the project on which it has the runtime dependency
as the jar had not been built.

This commit updates Boot's repackage task to have a dependency on the
jar task of any project dependencies in the runtime configuration
thereby ensuring that those dependencies' jars will have been built
before the repackaging occurs.

Fixes gh-2344

Running the invoker plugin with multiple threads against an empty
Maven cache results in strange build failures where Maven claims that
it cannot find a jar or pom file for an artifact that it should be
able to find. It would appear that Maven is unable to cope with
concurrent writes to its cache.

This commit removes the usage of multiple threads that was introduced
in 4e907f19.

Fixes gh-2389

This test covers the code path that caused gh-2361 and also checks that,
when an additional metadata file is found, it’s correctly merged with
the other metadata.

Closes gh-2361

When running in Eclipse, by default Gradle builds its output into a
folder named bin. This commit update the annotation processor to remove
the failure assumption that the output will always be located beneath
a folder named classes.

Closes gh-2369
See gh-2361

The 3.1 release includes an important fix to restore JDK 6
compatibility with the Gradle plugin [1].

Closes gh-2260

[1] https://github.com/flyway/flyway/issues/779

If user runs an executable archive then it and its lib directory will be
on the classpath. Entries from loader.path take precedence in a way that
should make sense to users (earlier wins like in CLASSPATH env var).

Also added new integration tests to verify the behaviour (big improvement
on the old ones, which probably aought to be beefed up to the same
standard).

Fixes gh-2314

Closes gh-2373

Conflicts:
	spring-boot/src/main/resources/org/springframework/boot/logging/logback/defaults.xml

Closes gh-2366

See gh-2366

Closes gh-2381

ServletContextInitializerBeans handles existing registration beans and
also creates initializers for existing Servlet, Filter, etc beans.
Debug logging has been added to this class to improve things in three
main areas:

 - Distinguish between existing registration beans and those that are
   created to wrap a Servlet or Filter bean
 - Provide information about the resource (configuration class or XML)
   that resulted in the creation of the bean
 - Log information about EventListeners

Closes gh-2177

Previously, SampleIntegrationParentApplicationTests assumed that when
an output file existed on disk its contents would have been written
in their entirety. This assumption does not hold true and causes the
test to fail intermittently as it incorrectly determines that the test
has produced no output.

This commit updates the test to wait for up to 30 seconds for the
output files to appear on disk and for the expected content to be
found in one of those files. If the files exist but do not
contain the expected content the test will keep trying until it does
or until too much time as elapsed.

Fixes gh-2380

Closes gh-2348

Previously, when JpaProperties was applying additional properties it
discarded any existing properties. This meant that custom
configuration of Hibernate's JtaPlatform was not detected and that
Boot's SpringJtaPlatform would always be configured instead.

This commit updates JpaProperties to include all of the existing
properties when it's asked to apply any additional properties.

See gh-2348
Closes gh-2359

Previously, the documentation only provided examples of the required
configuration for Maven users. This commit adds equivalent configuration
snippets for those using Gradle. It also removes the recommendation to
override the version of the Servlet API as this is unnecessary. The pom
files for the Jetty 8 and Tomcat 7 samples have also been updated
accordingly.

Closes gh-2346

Closes gh-2309

Java 8 introduced new, aggressive linting of javadoc that’s enabled by
default. The linter isn’t sufficiently configurable to allow us to tune
it to meet the project’s conventions for javadoc so our only realistic
option is to disable linting.

This commit introduces a new profile to disable javadoc linting. To
maintain compatibility with JDK 7, the profile is only active when the
build’s running on JDK 8 or later.

Closes gh-2233

* acceptcharset:
  Disable Accept-Charset Header in String converter

This commit prevents the `Accept-Charset` from being written by the
StringHttpMessageConverter. This feature is enabled by default in the
framework and writes a *quite long* response header with all charsets
supported by the server.

Closes gh-2370, see gh-1800

Undertow, like Tomcat, uses "" for the context path of the root
context. Previously, the Undertow deployment was being configured with
"/" for the root context. This was leading to a silent failure in
AsyncContextImpl.dispatch when it failed to look up the deployment
manager for the current request.

This commit updates UndertowEmbeddedServletContainerFactory to use the
correct context path (an empty String) for the root context.

Fixes gh-2365

Closes gh-2031

Jetty’s GzipFilter is a container-agnostic Filter that can be used to
provide gzip and deflate encoding of HTTP responses. This commit adds
auto-configuration for GzipFilter that is enabled when
org.eclipse.jetty:jetty-servlets is on the classpath. The filter can
be configured using spring.http.gzip.*

See gh-2031

Tomcat provide built-it support for gzip compression of HTTP responses.
This commit adds support for enabling and configuring this compression
via the environment using server.tomcat.compression and
server.tomcat.compressableMimeTypes.

See gh-2031

The ErrorPageFilter exposes a wrapped response to the downstream
chain and unless more care is taken the chain will be able to
set the response status, but not inspect it.

Fixes gh-2367

A dependency on org.glassfish.jersey.ext:jersey-bean-validation has
been added to spring-boot-starter-jersey. jersey-bean-validation’s EL
dependencies have been excluded in favour of those provided by
spring-boot-starter-tomcat (or starter-jetty or starter-undertow should
the user choose to use a different embedded container).

Closes gh-2315