Spring Boot 3.0.0 M3 Release Notes

For changes in earlier milestones, please refer to:

Upgrading from Spring Boot 2.x

Minimum Requirements Changes

None.

Actuator Metrics Export Properties

We have moved the properties controlling the actuator metrics export. The old schema was management.metrics.export.<product>, the new one is management.<product>.metrics.export (Example: the prometheus properties moved from management.metrics.export.prometheus to management.prometheus.metrics.export). If you are using the spring-boot-properties-migrator, you will get notified at startup. See #30381 for details.

Simplifed Main Class Name Resolution with Gradle

When building an application with Gradle, resolution of the name of the application’s main class has been simplified and made consistent. bootJar, bootRun, and bootWar now all resolve the name of the main class name by looking for it in the output of the main source set. This removes a small risk that the tasks may not have used the same main class name by default. If you were relying on the main class being resolved from a location outside of the main source set’s output, update your Gradle configuration to configure the main class name using the mainClass property of the springBoot DSL:

springBoot {
    mainClass = "com.example.Application"
}

Alternatively, you can configure the classpath property of the resolveMainClassName task to search in locations other than the main source set’s output directories.

Running Your Application in the Maven Process

The fork attribute of spring-boot:run and spring-boot:start that was deprecated in Spring Boot 2.7 has been removed.

New and Noteworthy

Tip	Check the configuration changelog for a complete overview of the changes in configuration.

Reinstated Support for REST Assured

With it’s 5.0 release, REST Assured is compatible with Jakarta EE 9 and Groovy 4.0. As a result, support has been reinstated.

Auto-configuration for Micrometer Observation API

Spring Boot now auto-configures an instance of ObservationRegistry for you. If micrometer-core is on the classpath, a TimerObservationHandler is registered on the ObservationRegistry, which means that every stopped Observation leads to a timer. ObservationPredicate, GlobalTagsProvider and ObservationHandler are automatically registered on the ObservationRegistry. You can use ObservationRegistryCustomizer to further customize the ObservationRegistry if you need to. See #29666 for details.

Auto-configuration for Micrometer Tracing

Spring Boot now auto-configures Micrometer Tracing for you. This includes support for Brave, OpenTelemetry, Zipkin and Wavefront. When using the Micrometer Observation API, finishing observations will lead to spans reported to Zipkin or Wavefront. Tracing can be controlled with properties under management.tracing. Zipkin can be configured with management.zipkin.tracing, while Wavefront uses management.wavefront. To use, for example Wavefront with Brave, these dependencies are needed:

implementation 'org.springframework.boot:spring-boot-starter-actuator'
implementation 'io.micrometer:micrometer-tracing-bridge-brave'
implementation 'io.micrometer:micrometer-tracing-reporter-wavefront'

See the documentation (TBD) for more details.

Dependency Upgrades

Spring Boot 3.0.0-M3 moves to new versions of several Spring projects:

TBD

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

REST Assured 5.0

Miscellaneous

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

TBD

Deprecations in Spring Boot 3.0

The properties management.metrics.export.<product> are deprecated, the replacement is management.<product>.metrics.export. See above for more details.