Rework the ConfigurationPropertySources and related adapter classes to
help with performance. The ConfigurationPropertySources class now only
monitors for updates when `.attach` is used. The `.get` methods now
return the adapted version, but no longer checks to see if sources have
been added or removed on each call.
This commit also fixes a few caching issues and makes both the
`PropertyMapper` implementations true static singletons.
See gh-9000
CachePublicMetrics wasn't explicitly tested and was still using field
injection. This commit improves the situation in preparation of the fix
for gh-8984
Update `ValidationAutoConfiguration` and `WebMvcAutoConfiguration` to
ensure as much as possible that only a single Validator bean of each
type is registered.
Validation auto-configuration now does the following:
- If no validator is found: Registers a `LocalValidatorFactoryBean`
(providing both Spring and JSR validation)
- If the user defines a Spring & JSR validator: Backs off
- If the user defines only a JSR validator: Adapts it to a Spring
validator (without exposing another JSR implementation)
WebMvcAutoConfiguration auto-configuration has been updated to make
MVC validation follow common Spring Boot patterns:
- If not validator beans are found (due to the user excluding
ValidationAutoConfiguration) a new `mvcValidator` bean will be
registered.
- If a single validator bean is found it will be used for MVC
validation.
- If multiple validator beans are defined it will either use the one
named `mvcValidator` or it will register a new `mvcValidator` bean
Any automatically registered `mvcValidator` bean will not implement
the JSR validator interface.
Finally, it is no longer possible to provide an MVC validator via a
`WebMvcConfigurer`.
Fixes gh-8495
Allow `PathExtensionContentNegotiationStrategy` to be bypassed by
actuator endpoints. Prior to this commit calling `/loggers/com.aaa.cab`
would return a HTTP 406 response due to `.cab` being a known extension.
Fixes gh-8765
