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 name 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.

Minimum Requirements Changes

None.

New and Noteworthy

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

Dependency Upgrades

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

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

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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