Spring Boot 4.2.0-M1 Released: RestTemplate Deprecated, AMQP 1.0 Support Added, Major Dependency Upgrades

Overview

Spring Boot 4.2.0-M1 is the first milestone release of the Spring Boot 4.2 series, available from Maven Central as a pre-release version. It includes breaking feature enhancements, dependency upgrades, and bug fixes.

New Features

Improved Jetty server forwarded request header configuration.

Disabled Micrometer global Registry by default in test environments to reduce test context pollution from global state.

Jetty graceful shutdown now uses GracefulHandler for coordination instead of StatisticsHandler.

Marked Spring Boot's RestTemplate support as deprecated; the direct replacement is RestClient. Both are synchronous, blocking HTTP clients, so existing Spring MVC projects need not forcibly adopt reactive programming.

Marked TestRestTemplate as deprecated; recommended replacement is RestTestClient.

Adjusted forwarded header configuration to align with Reactor Netty and Spring Framework changes.

Removed deprecated APIs scheduled for removal in Spring Boot 4.2 (see Deprecated API Removals section).

Buildpacks added image-based build cache support.

Provided plugin version management for hibernate-maven-plugin.

Added timeout configuration to RetryPolicySettings.

Added self-reference return to ApplicationContextAssertProvider.

Kafka Streams added leaveGroupOnClose configuration property. ApplicationHome and ApplicationTemp gained Path -based access methods.

Official AMQP 1.0 support added, including generic AMQP 1.0 client and RabbitMQ-specific AMQP 1.0 client with RabbitMQ-exclusive features.

Renamed spring-boot-amqp to spring-boot-rabbitmq.

Improved spring-boot.run.useTestClasspath handling of target/test-classes.

Deprecated API Removals

The following deprecated classes have been removed:

EnvironmentPostProcessor

HttpMessageConverters

ZipkinWithOpenTelemetryTracingAutoConfiguration

DeprecatedMongoDbContainerConnectionDetailsFactory

DeprecatedNeo4jContainerConnectionDetailsFactory

DeprecatedPulsarContainerConnectionDetailsFactory

DeprecatedRabbitContainerConnectionDetailsFactory

DeprecatedMariaDbR2dbcContainerConnectionDetailsFactory

DeprecatedMySqlR2dbcContainerConnectionDetailsFactory

DeprecatedPostgresR2dbcContainerConnectionDetailsFactory

DeprecatedSqlServerR2dbcContainerConnectionDetailsFactory

RestTemplate Migration

The direct replacement for RestTemplate is RestClient. Both are synchronous, blocking HTTP clients, so existing traditional Spring MVC projects do not need to forcibly rewrite to reactive programming for this deprecation.

Bug Fixes

Fixed structured logging JSON encoding failure potentially contaminating the next log on the same thread.

Fixed Kafka consumer dedicated security protocol configuration not taking effect.

No longer incorrectly exposes gRPC test server port when gRPC is not introduced.

Fixed Micrometer Registry holding application context, preventing context release.

Fixed temporary files not deleted after exported image TAR build failure.

Fixed spring.grpc.server.health.include-overall-health configuration not taking effect.

Fixed configuration metadata processor ignoring @NestedConfigurationProperty on record getters.

Fixed spring-boot-h2-console incorrectly pulling in Servlet API.

Fixed PropertiesLauncher not logging nested archive paths.

Corrected missing @Nullable declaration on some Map#remove return methods.

Fixed Flyway subdirectory migration paths being flattened in Native Image environments.

Fixed Kotlinx Serialization CodecCustomizer ordering issue.

Fixed JarFile not closed when locating main class from archive files.

Dependency Upgrades

Hibernate ORM 7.4.5.Final

Hibernate Validator 9.1.3.Final

Jackson 3.1.5, Jackson 2.21.5

Kafka 4.3.1

Kotlin 2.4.10

JUnit Jupiter 6.1.3

Jetty 12.1.12

Tomcat 11.0.24

Netty 4.2.17.Final

Flyway 12.11.0

Elasticsearch Client 9.5.0

Jedis 8.0.0

Lettuce 7.6.0.RELEASE

HikariCP 7.1.0

Log4j 2.26.1

Logback 1.6.1

OpenTelemetry 1.64.0

gRPC Java 1.83.1

Gson 2.14.0

PostgreSQL JDBC 42.7.13

Pulsar 4.2.4