정리중

https://docs.spring.io/spring-boot/docs/2.6.0-SNAPSHOT/reference/html/
https://docs.spring.io/spring-boot/docs/2.6.0-SNAPSHOT/actuator-api/html/

Spring Boot 2.6.0 M1 Release Note

Upgrading from Spring Boot 2.5

Embedded Mongo

To use embedded mongo, the spring.mongodb.embedded.version property must now be set.
This helps to ensure that the MongoDB version that is used by the embedded support matches the MongoDB version that your application will use in production.

Nimbus DS Dependency Management Removed

Dependency management for com.nimbusds:oauth2-oidc-sdk and com.nimbusds:nimbus-jose-jwt has been removed.
If you are using Spring Security you should rely on the versions that it will pull in as transitive dependencies.
If you are not using Spring Security you should define your own dependency management that meets your application's needs.

HAL Browser Dependency Management Removed

Dependency management for org.webjars:hal-browser has been removed.
If you are using org.webjars:hal-browser you should define your own dependency management that meets your application's needs.

Maven Build Info's Default Time

The Maven plugin's build info support now uses the value of the project.build.outputTimestamp property as the default build time.
If the property is not set, the the build session's start time is used as it was previously.
As before, the time can be disabled entirely by setting it to off.

Prometheus Version Property

The property to control the version of Prometheus has changed from prometheus-pushgateway.version to prometheus-client.version. This is to reflect the fact that the property manages the version of every module in Prometheus's client, not just the pushgateway.

Deprecations from Spring Boot 2.4

Classes, methods and properties that were deprecated in Spring Boot 2.4 have been removed in this release.
Please ensure that you aren't calling deprecated methods before upgrading.

Minimum requirements changes

None.

New and Noteworthy

TIP: Check link:Spring-Boot-2.6.0-M1-Configuration-Changelog[the configuration changelog] for a complete overview of the changes in configuration.

Auto-configuration for Spring Data Envers

Auto-configuration for Spring Data Envers is now provided.
To use it, add a dependency on org.springframework.data:spring-data-envers and update your JPA repositories to extend from RevisionRepository.

Exporting Metrics to the Dynatrace v2 API

Support for exporting metrics to the Dynatrace v2 API has been added.
With a local OneAgent running on the host, a dependency on io.micrometer:micrometer-registry-dynatrace is all that is required.
Without a local OneAgent, the management.metrics.export.dynatrace.uri and management.metrics.export.dynatrace.api-token properties must be configured.
Other settings that are specific to the v2 API can be configured using the management.metrics.export.dynatrace.v2 properties.
Please refer to the {docs}/actuator.html#actuator.metrics.export.dynatrace[updated reference documentation] for further details.

Task Execution and Scheduling Metrics

Micrometer's ExecutorServiceMetrics are now auto-configured for all ThreadPoolTaskExecutor and ThreadPoolTaskScheduler beans, as long as the underlying ThreadPoolExecutor is available.
Metrics are tagged with the name of the executor derived from its bean name.

Disk Space Metrics

Micrometer's DiskSpaceMetrics are now auto-configured.
disk.free and disk.total metrics are provided for the partition identified by the current working directory.
To change the path that is used, define your own DiskSpaceMetrics bean.

Jetty Connection and SSL Metrics

Micrometer's JettyConnectionMetrics are now auto-configured.
Additionally, when server.ssl.enabled is set to true, Micrometer's JettySslHandshakeMetrics are also auto-configured.

Redis Connection Pooling

Redis (both Jedis and Lettuce) will now automatically enable pooling when commons-pool2 is on the classpath.
Set spring.redis.jedis.pool.enabled or spring.redis.lettuce.pool.enabled to false to disable pooling if required.

Improved Configuration of the Maven Plugin's Start Goal

The Maven Plugin's start goal has been made more configurable from the command line.
Its wait and maxAttempts properties can be specified using spring-boot.start.wait and spring-boot.start.maxAttempts respectively.

Auto-configured Spring Web Service Server Tests

A new annotation, @WebServiceServerTest, that can be used to test Web Service @Endpoint beans has been introduced.
The annotation creates a test slice containing @Endpoint beans and auto-configures a MockWebServiceClient bean that can be used to test your web service endpoints.

Dependency Upgrades

Spring Boot 2.6 moves to new versions of several Spring projects:

• https://spring.io/blog/2021/07/19/spring-security-5-6-0-m1-released[Spring Security 5.6.0-M1]
• https://spring.io/blog/2021/07/16/spring-data-2021-1-0-m1-released[Spring Data 2021.1.0-M1]
• https://github.com/spring-projects/spring-hateoas/releases/tag/1.4.0-M1[Spring HATEOAS 1.4.0-M1]
• https://github.com/spring-projects/spring-kafka/releases/tag/v2.8.0-M1[Spring Kafka 2.8.0-M1]
• https://github.com/spring-projects/spring-amqp/releases/tag/v2.4.0-M1[Spring AMQP 2.4.0-M1]

Numerous third-party dependencies have also been updated, some of the more noteworthy of which are the following:

• Micrometer 1.8.0-M1
• QueryDSL 5.0.0.M1
• SnakeYAML 1.29
• Cassandra Driver 4.12.0
• Kafka 2.8.0

Miscellaneous

Apart from the changes listed above, there have also been lots of minor tweaks and improvements including:

• The failure analysis for a NoSuchMethodError now includes information about the location from which the calling class was loaded.
• A ClientResourcesBuilderCustomizer bean can now be defined to customize Lettuce's ClientResources will retaining the default auto-configuration.
• Configuration properties for Flyway's detectEncoding, failOnMissingLocations, and ignoreMigrationPatterns configuration settings have been added.
• A custom ResourceLoader to be used by the application can be provided when creating a SpringApplicationBulder.
• A WebSessionIdResolver can now be defined to customize the resolver that will be used by the auto-configured WebSessionManager.
• Any RSocketConnectorConfigurer beans are now automatically applied to the auto-configured RSocketRequester.Builder.
• spring-boot-configuration-processor can now generate metadata for classes annotated with Lombok's @Value.
• A new server.tomcat.reject-illegal-header configuration property can be set to true to configure Tomcat to accept illegal headers.
• When using Stackdriver, labels can now be configured on the monitor resource by setting management.metrics.export.stackdriver.resource-labels.* configuration properties.
• @EntityScan now supports comma-separated values in its basePackages attribute.
• A new configuration property, server.netty.idle-timeout, that can be used to control Reactor Netty's idle timeout has been added.
• The location from which Devtools loads its global settings can now be configured using the spring.devtools.home system property or the SPRING_DEVTOOLS_HOME environment variable.
• The setter methods on RabbitTemplateConfigurer are now public

Deprecations in Spring Boot 2.6.0 M1

• AbstractDataSourceInitializer has been deprecated in favor of DataSourceScriptDatabaseInitializer.
  Similarly, subclasses of AbstractDataSourceInitializer have been deprecated in favour of new DataSourceScriptDatabaseInitializer-based equivalents.
• SpringPhysicalNamingStrategy has been deprecated in favor of Hibernate 5.5's CamelCaseToUnderscoresNamingStrategy