Spring Boot 4.0.0 M3 Release Notes

Spring Boot 4.0.0-M3 Release Notes

For changes in earlier milestones, please refer to:

Upgrading from Spring Boot 3.5

Migration Guide

To help with upgrading, a migration guide is available.

Jackson

Spring Boot now uses Jackson 3 as its preferred JSON library. Jackson 3 uses new group IDs and package names with com.fasterxml.jackson becoming tools.jackson. An exception to this is the jackson-annotations module which continues to use the com.fasterxml.jackson.core group ID and com.fasterxml.jackson.annotation package. To learn more about the changes in Jackson 3, refer to the Jackson wiki.

For libraries that require Jackson 2, dependency management for Jackson 2 remains and a manually configured Jackson 2 ObjectMapper can be used alongside Boot’s auto-configuration for Jackson 3 if needed.

MongoDB UUID and BigDecimal Representations

Spring Data MongoDB no longer provide defaults for UUID and BigInteger/BigDecimal representations. This aligns with the driver recommendation to not favor a particular representation for UUID or BigInteger/BigDecimal to avoid representation changes caused by upgrades to a newer Spring Data version.

An explicit configuration is expected and the representations can be set using the spring.mongodb.representation.uuid and spring.data.mongodb.representation.big-decimal properties, respectively.

Dependency Management for Spring Retry

With the portfolio moving from Spring Retry to new core features of Spring Framework, dependency management for Spring Retry has been removed.

If your application still relies on Spring Retry, an explicit version is now required. Please consider moving your use of Spring Retry to Spring Framework.

Spring Kafka Retry Features

Spring Kafka has moved its retry capabilities from Spring Retry to Spring Framework.

As a result, spring.kafka.retry.topic.backoff.random has been removed in favor of spring.kafka.retry.topic.backoff.jitter. The latter provides more flexibility over the latter, see the documentation for more details.

Spring AMQP Retry Features

Spring AMQP has moved its retry capabilities from Spring Retry to Spring Framework.

Spring Boot offers a customization hook-point for retry features used by the RetryTemplate and message listeners. To make it more explicit, two dedicated customizers have been introduced: RabbitTemplateRetrySettingsCustomizer, and RabbitListenerRetrySettingsCustomizer.

If you were using RabbitRetryTemplateCustomizer to customize the retry settings according to a target, you will need to migrate to either of those interfaces.

Property Mapper API Changes

The PropertyMapper class no longer calls adapter or predicate methods by default when the source value is null. This has removed the need for the alwaysApplyingNotNull() method which has been removed.

If you need to perform a mapping even for null values you can use the new always() method.

For example,

map.from(source::method).to(destination::method);

Will not call destination.method(…) if source.method() returns null.

Where as:

map.from(source::method).always().to(destination::method);

Will call destination.method(null) if source.method() returns null.

If you use the PropertyMapper, you might want to review commit 239f384ac0 which shows how Spring Boot itself adapted to the new API.

Optional Actuator Endpoint Parameters

Optional actuator endpoint parameters must now be annotated with JSpecify’s @Nullable. The previously introduced @OptionalParameter has been removed in this milestone. If you were using it, please use org.jspecify.annotations.Nullable instead.

Minimum Requirements Changes

None.

New and Noteworthy

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

MongoDB

Health Indicators

The MongoDB health indicators have been reworked so that they no longer require Spring Data MongoDB. This allows health information to be provided when using the MongoDB Java Driver directly.

As part of this change, the health indicators have moved from spring-boot-data-mongodb to spring-boot-mongodb. Their packages have also been updated accordingly.

Properties

A new property, spring.data.mongodb.representation.big-decimal, has been introduced to control how Spring Data MongoDB stores BigDecimal (and BigInteger) values in MongoDB.

A number of properties have also been renamed. See the migration guide for details.

Jackson

spring.jackson.datetime.<feature-name> properties can be used to enable and disable DataTimeFeature settings on the auto-configured JsonMapper.

Dependency Upgrades

Spring Boot 4.0.0-M3 moves to new versions of several Spring projects:

…

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

Jedis 6.2.0

Miscellaneous

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

Log4j Core configuration file detection for Log4j 3 has been improved
Resource lookup in DevTools restart has been optimized
ScheduledTasksObservabilityAutoConfiguration has been renamed to ScheduledTasksObservationAutoConfiguration for consistency
Authenticating with Elasticsearch using an API key is now supported using the new spring.elasticsearch.api-key property.
ConditionalOnEnabledTracing has been renamed to ConditionalOnEnabledTracingExport
The property management.tracing.enabled has been renamed to management.tracing.export.enabled