Previously, the database configured with spring.data.redis.database (or in spring.data.redis.url) was silently ignored when spring.data.redis.masterreplica.nodes was set, and the connection factory always used database 0. The configured database is now applied to master/replica connections, as it already was for standalone and Sentinel setups.

You may be impacted if you set a database together with master/replica nodes, as your application will now read from and write to that database instead of database 0. If you were relying on database 0, remove the spring.data.redis.database property (or the database segment of spring.data.redis.url), or set it to 0 explicitly.

With server.forward-headers-strategy=native, Reactor Netty no longer uses the X-Forwarded-Prefix header to determine the context path. The same applies to the framework strategy with WebFlux.

If your proxy sets the header and you rely on it, set server.netty.forwarded-headers.use-forwarded-prefix (native) or spring.webflux.forwarded-headers.use-forwarded-prefix (framework) to true.

SSL bundle options.ciphers and options.enabled-protocols were silently ignored by components that cannot apply them. The application now fails to start if an SSL bundle with options is used by:

• gRPC clients and servers

• the LDAP client and the embedded LDAP server

• OTLP tracing and logging exporters

This is consistent with MongoDB and Couchbase. If you’re impacted, remove the options from the bundle, or use a separate bundle without options for these components.

The RabbitMQ AMQP 1.0 support introduced in 4.2.0-M1 has been refined:

• spring.amqp.rabbitmq.username and spring.amqp.rabbitmq.password no longer default to guest. Without credentials, the client authenticates anonymously. The same applies to RabbitMQ Docker Compose integration when RABBITMQ_DEFAULT_USER and RABBITMQ_DEFAULT_PASS are not set.

• The port defaults to 5671 when spring.amqp.rabbitmq.ssl.bundle is set.

• spring.amqp.rabbitmq.template.exchange and spring.amqp.rabbitmq.template.routing-key no longer default to an empty string, as the AMQP 1.0 template does not support the default exchange.

• The health indicator key is now amqprabbit instead of rabbit, so that it can co-exist with the AMQP 0.9 health indicator. Use management.health.amqprabbit.enabled to disable it, and update health group includes accordingly.

Spring Boot 4.2.0-RC2 moves to new versions of several Spring projects:

• Micrometer 1.18.0-RC2

• Micrometer Tracing 1.8.0-RC2

• Spring Framework 7.1.0-RC2

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

• ActiveMQ 6.3.3

• AspectJ 1.9.27

• Byte Buddy 1.18.17

• Hibernate 7.4.14.Final

• Infinispan 16.3.1

• Jackson 2 Bom 2.21.8

• Jackson Bom 3.1.8

• Json-smart 2.6.1

• MariaDB 3.5.11

• Maven Failsafe Plugin 3.6.1

• Maven Surefire Plugin 3.6.1

• MSSQL JDBC 13.6.2.jre11

• MySQL 26.10.0

• Native Build Tools Plugin 1.1.18

• Netty 4.2.20.Final

• Protobuf Maven Plugin 5.1.12

• UnboundID LDAPSDK 7.0.6

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

• SSL bundle reloading is no longer supported by the LDAP client, as there is no official API to support it.

• Setting management.observations.conventions to open-telemetry now enables OpenTelemetry’s semantic conventions, as documented. Previously, neither Micrometer’s nor OpenTelemetry’s conventions were applied.