- Add @author tag
 - Remove unnecessary final modifiers
 - Avoid writing to volatile field when new gauge is used

Closes gh-3977

The previous implementation would remove and add a new Gauge each time
a metric was written. After this change the Gauge is registered once
and the value is updated on subsequent calls.

See gh-3997

This commit reverts the changes made for gh-4026. Those changes updated
each LoggingSystem to close/stop the underlying logging system as part
of the clean up processing. Unfortunately, this approach doesn’t work
in an environment where their are multiple application contexts and
some have a shorter lifecycle than the “main” application context. In
such an environment, closing an application context with a shorter
lifecycle prior to the main application context being closed will
close/stop the main application context’s logging system as, rather than
being scoped to an application context, a logging system is shared
across multiple application contexts. (The exact details of how widely
shared the logging system is varies between logging systems and, in the
case of Logback and Log4J2, also depends on which ContextSelector
implementation is being used.

Closes gh-2516

* pr/4054:
  Fix typo

Closes gh-4054

Update RelaxedDataBinder so that both `.` and `_` are considered in
getPropertyValuesForNamePrefix(...).

With Spring Boot 1.2.5 binding environment variables of the form
`FOO_BAR_BAZ` to `@ConfigurationProperties(prefix="foo-bar")` objects
worked thanks to a happy accident. When `PropertySourcesPropertyValues`
processed a non enumerable `PropertySource` it called the resolver
with a property name `FOO_BAR.BAZ`. A `SystemEnvironmentPropertySource`
will replace `.` with `_` and hence find a value.

Commit 1abd0879 updated non enumerable processing such that the resolver
was never called.

Replicating the problem is quite involved as you need to ensure that you
have both a SystemEnvironmentPropertySource and a non-enumerable
property source (e.g. RandomPropertySource). A test has been added to
PropertiesConfigurationFactoryTests which passes on 1.2.5, fails on
1.2.6 and passes again following this commit.

Fixes gh-4045

This commit updates a number of tests in spring-boot to ensure that
they close the application contexts that they create. SimpleMainTests
still create a number of contexts that are not closed as there’s no
(easy) way to get hold of the context when testing the main method.

See gh-4053

See gh-4026

Previously, when a LoggingSystem was cleaned up the underlying logging
system (LogBack, Log4J, Log4J2, JUL) was not being properly shut down.
LogBack explicitly recommends stopping it cleanly [1]. While the other
logging systems are less explicity about it, they would all appear to
benefit from being stopped.

This commit updates all four LoggingSystems to stop/reset/clean up to
underlying logging system when cleanUp is called.

Closes gh-4026

[1] http://logback.qos.ch/manual/configuration.html#stopContext

See gh-2445

This commit adds auto-configuration support for WebSocket-based
messaging. When the user enables WebSocket messaging (typically via
@EnableWebSocket and @EnableWebSocketMessageBroker) and an ObjectMapper
bean exists, a MappingJackson2MessageConverter that uses the
ObjectMapper will be configured. This causes any spring.jackson.*
configuration to affect WebSocket message conversion in the same way
as it affects HTTP message conversion.

Closes gh-2445

Closes gh-3808

The code that uses reflection to determine the protocol and port has
been updated to align with changes made in Undertow 1.3

See gh-3969

Follow-on from c55900b4.

Closes gh-3891

See gh-3969

Update TomcatEmbeddedServletContainerFactory to provide a better error
message when attempting to load classpath resources.

Fixes gh-2635

Update SpringApplicationContextLoader to detect xml and groovy
configuration based on convention.

Fixes gh-2516

Update HealthMvcEndpoint so that relaxed names can be used as keys in
the `endpoints.health.mapping` property.

Fixes gh-2465

Update RemoteSpringApplication so that initializers and listeners are
prescribed and not loaded from spring.factories.

Fixes gh-3925

* gh-2371:
  Support `error.include-stacktrace` configuration

Add `error.include-stacktrace` configuration option to determine when
stack trace attributes should be added. Options are `never`, `always`
or `on-trace-param`.

Prior to this commit stacktrace attributes were never includes in HTML
responses, and only included in JSON responses when a `trace` request
parameter was set to `true`. This has now been changed so that,
by default, stacktrace attributes are never included.

The BasicErrorController includes a protected method that can be
overridden if includes should be different depending on the `produces`
mapping.

Closes gh-2371

Fixes gh-3782

See gh-2064

Use SNAPSHOT build in preparation for 4.2.2.

See gh-4020

Update MetricsFilter to use static `Pattern` instances for regex
replacements rather than compiling them each time.

Fixes gh-3996

See gh-2064

* gh-2214:
  Add Cassandra support

Add auto-configuration support and health checks for Cassandra and
Spring Data Cassandra.

Fixes gh-2064
Closes gh-2214

This commit simplifies the Jackson-related auto-configuration that’s
applied when Spring HATEOAS and Spring Data REST are on the classpath.

Previously, Boot used Jackson2HalModule to apply the HAL-related
ObjectMapper configuration to the context’s primary ObjectMapper. This
was to allow HAL-formatted responses to be sent for requests accepted
application/json (see gh-2147). This had the unwanted side-effect of
polluting the primary ObjectMapper with HAL-specific functionality.
Furthermore, Jackson2HalModule is an internal of Spring HATEOAS that
@olivergierke has asked us to avoid using.

This commit replaces the use of Jackson2HalModule with a new approach.
Now, the message converters of any RequestMappingHandlerAdapter beans
are examined and any TypeConstrainedMappingJackson2HttpMessageConverter
instances are modified to support application/json in addition to their
default support for application/hal+json. This behaviour can be disabled
by setting spring.hateoas.use-hal-as-default-json-media-type to false.
This property is named after Spring Data REST’s configuration option
which has the same effect when using Spring Data REST. The new property
replaces the old spring.hateoas.apply-to-primary-object-mapper property.

Previously, when Spring Data REST was on the classpath,
JacksonAutoConfiguration would be switched off resulting in the context
containing multiple ObjectMappers, none of which was primary.

This commit configures RepositoryRestMvcAutoConfiguration to run after
JacksonAutoConfiguration. This gives the latter a chance to create its
primary ObjectMapper before the former adds its ObjectMapper beans to
the context.

Previously, the actuator’s hypermedia support assumed that the
HttpMessageConverters bean would contain every HttpMessageConverter
being used by Spring MVC. When Spring HATEOAS is on the classpath this
isn’t the case as it post-processes RequestMappingHandlerAdapter beans
and adds a TypeConstrainedMappingJackson2HttpMessageConverter to them.
This wasn’t a problem in the past as the primary ObjectMapper, used by a
vanilla MappingJackson2HttpMessageConverter, was configured with Spring
HATEOAS’sJackson2HalModule. Now that this pollution has been tidied up
the assumption described above no longer holds true. MvcEndpointAdvice,
which adds links to the actuator’s json responses, has been updated
to look at the HttpMessageConverters of every
RequestMappingHandlerAdapter when it’s trying to find a converter to
use to write a response with additional hypermedia links.

Integration tests have been added to spring-boot-actuator to ensure
that the changes described above have not regressed the ability to
configure its json output using spring.jackson.* properties (see
gh-1729).

Closes gh-3891