Upgrade to Spring Boot 4.0.0 with Spring Cloud 2025.1.0

[adityamparikh]

Summary

• Upgrade all 77 modules from Spring Boot 2.3–3.1 to Spring Boot 4.0.0 with Spring Cloud Stream 5.0.0 and Spring Cloud 2025.1.0 (Oakwood)
• Centralize POM hierarchy: all leaf modules now inherit from a single root parent instead of individual spring-boot-starter-parent declarations, eliminating duplicated dependency management across ~40 modules
• Full test suite passes: ./mvnw install completes with BUILD SUCCESS across all modules

Migration details

Area	Changes
Build	Centralized POM hierarchy, BOM-managed dependencies, removed ~40 duplicate <dependencyManagement> blocks
Jakarta	javax.persistence, javax.validation, javax.transaction, javax.annotation → jakarta.*
Kafka Streams 4.0	KStream.branch(Predicate...) → split().branch() API; TopologyTestDriver → TestInputTopic/TestOutputTopic; cache.max.bytes.buffering → statestore.cache.max.bytes
Spring Kafka 4.0	EmbeddedKafkaRule → @EmbeddedKafka / EmbeddedKafkaKraftBroker; KafkaTestUtils int timeouts → Duration
Spring Cloud Stream 5.0	serdeError → deserializationExceptionHandler; spring.cloud.stream.function.definition → spring.cloud.function.definition
Spring Boot 4.0	Modular auto-config package relocations; spring.profiles → spring.config.activate.on-profile; spring-boot-starter-webflux-test for relocated AutoConfigureWebTestClient
Testing	@SpyBean → @MockitoSpyBean; JUnit 4 → JUnit 5 throughout; @DynamicPropertySource for embedded Kafka setup
Kotlin	kotlin-stdlib-jdk8 → kotlin-stdlib; removed pinned Kotlin versions (Boot-managed)
Security	Lambda DSL migration (.csrf().disable() → .csrf(csrf -> csrf.disable()))
Dependencies	Removed hardcoded versions for kafka-streams-test-utils, Confluent, Avro, Testcontainers, MariaDB, etc. in favor of BOM management

Modules affected

All 18 top-level module groups (127 files changed, 915 insertions, 3837 deletions):

confluent-schema-registry-integration · function-based-stream-app-samples · kafka-batch-sample · kafka-binder-native-app · kafka-e2e-kotlin-sample · kafka-native-serialization · kafka-security-samples · kafka-streams-samples (17 sub-modules) · kinesis-samples · kotlin-rabbit-functions · multi-binder-samples (6 sub-modules) · multi-functions-samples · partitioning-samples · routing-samples · schema-registry-integration · batch-producer-consumer · testing-samples · transaction-kafka-samples

Test plan

• ./mvnw install --fail-at-end passes with BUILD SUCCESS across all 77 modules
• All Kafka Streams topology tests pass (branching, word-count, inventory-count, aggregate, DLQ, recoverable)
• All multi-binder tests pass (two-kafka-clusters, sendto-dest-header, kafka-streams)
• Schema registry consumer test passes with stub client
• Testing-demo JDBC sink test passes with embedded Kafka
• Kafka batch sample test passes with @EmbeddedKafka

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