Brian Clozel 97af0b2f3a Add actuator specific ObjectMapper
Prior to this commit, Actuator endpoints would use the application
ObjectMapper instance for serializing payloads as JSON. This was
problematic in several cases:

* application-specific configuration would change the actuator endpoint
output.
* choosing a different JSON mapper implementation in the application
would break completely some endpoints.

Spring Boot Actuator already has a hard dependency on Jackson, and this
commit uses that fact to configure a shared `ObjectMapper` instance that
will be used by the Actuator infrastructure consistently, without
polluting the application context.

This `ObjectMapper` is used in Actuator for:

* JMX endpoints
* Spring MVC endpoints with an HTTP message converter
* Spring WebFlux endpoints with an `Encoder`
* Jersey endpoints with a `ContextResolver<ObjectMapper>`

For all web endpoints, this configuration is limited to the
actuator-specific media types such as
`"application/vnd.spring-boot.actuator.v3+json"`.

Fixes gh-12951
2020-02-12 20:10:25 +01:00
..
2020-02-12 20:10:25 +01:00

= Spring Boot - Actuator

Spring Boot Actuator includes a number of additional features to help you monitor and
manage your application when it's pushed to production. You can choose to manage and
monitor your application using HTTP or JMX endpoints. Auditing, health and metrics
gathering can be automatically applied to your application. The
https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready[user guide]
covers the features in more detail.

== Enabling the Actuator
The simplest way to enable the features is to add a dependency to the
`spring-boot-starter-actuator` '`Starter`'. To add the actuator to a Maven-based project,
add the following '`Starter`' dependency:

[source,xml,indent=0]
----
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>
	</dependencies>
----

For Gradle, use the following declaration:

[indent=0]
----
	dependencies {
		implementation 'org.springframework.boot:spring-boot-starter-actuator'
	}
----

== Features
* **Endpoints** Actuator endpoints allow you to monitor and interact with your
  application. Spring Boot includes a number of built-in endpoints and you can also add
  your own. For example the `health` endpoint provides basic application health
  information. Run up a basic application and look at `/actuator/health`.
* **Metrics** Spring Boot Actuator provides dimensional metrics by integrating with
  https://micrometer.io[Micrometer].
* **Audit** Spring Boot Actuator has a flexible audit framework that will publish events
  to an `AuditEventRepository`. Once Spring Security is in play it automatically publishes
  authentication events by default. This can be very useful for reporting, and also to
  implement a lock-out policy based on authentication failures.