spring-boot-4-lifecycle-migration

name	spring-boot-4-lifecycle-migration
description	Migrates Inera intyg Java apps from Spring Boot 3.5.x / Gradle 8.14.x / Jackson 2 to Spring Boot 4.1.0 / Gradle 9.6.0 / Jackson 3 using phased, verifiable steps. Use when lifecycle migration, Java 25 upgrade, intyg-bom bump, Jackson 3 migration, Gradle 9 upgrade, or Spring Boot 4 migration is requested for intyg projects.

Spring Boot 4 lifecycle migration (Inera intyg)

Generalized workflow from minaintyg (K1J-2265). Adapt per project; do not assume every Jira item applies.

Primary references

• Spring Boot 4.0 Migration Guide
• intyg-bom (target: 1.0.0.16 or later — Java 25, Gradle 9.6.0, Spring Boot 4.1.0)
• Prior migration docs in repo: LIFECYCLE-MIGRATION-PLAN.md, LIFECYCLE-MIGRATION-PROGRESS.md, SPRING-BOOT-4-AUDIT.md

Detailed starter/API mappings: reference.md

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Jira acceptance criteria (standard)

The application must build, pass unit and integration tests, start, and behave as before while running on:

Target	Default version
Java	25
Spring Boot (+ BOM)	4.1.0 (latest stable 4.x at migration time)
Gradle	9.6.0
Jackson	3 (tools.jackson.*)
Builder image tag	25.0.3
Runtime image tag	25.0.1

Also required:

• Updated dependencies and plugins (via intyg-bom + project-specific bumps)
• Use Spring Boot starters and auto-configuration wherever practical
• No Jackson 2 compatibility layer — full Jackson 3 adoption

Jira description goals (interpret per repo):

• Java 21 → 25, Spring Boot 3 → 4, Gradle 8 → 9
• Replace remaining manual Spring config with Boot starters/autoconfig (ActiveMQ, Camel, etc.) where the project actually uses them
• Update builder/runtime images
• Follow the Spring Boot 4 Migration Guide

Stop and ask the user before assuming:

• Jira ticket number and commit prefix (K1J-XXXX:)
• External schema artifact version bumps
• dependencies.common.version applicability (only if project depends on intyg-common)
• Analytics or API schemaVersion changes
• Whether Gradle wrapper upgrade is manual (team-owned step)

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Migration principles

1. Phased and verifiable — green build (or documented expected partial failure) before next phase
2. Stop between phases — propose commit message; do not commit unless asked
3. Minimal behaviour change — lifecycle migration, not opportunistic refactors
4. Document deviations — accepted manual beans, deferred RestClient/RestTestClient, etc.
5. Project inventory first — not every Jira bullet applies (wsdl2java, Camel, intyg-common)

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Default version targets

Property	From (typical)	To
intygBomVersion	1.0.0.14	1.0.0.16+
Gradle wrapper	8.14.4	9.6.0
Spring Boot	3.5.x (via BOM)	4.1.0
Jackson	2.x	3.x
Java toolchain	21	25

Verify resolved versions after BOM bump:

./gradlew --version
./gradlew properties | grep -E 'javaVersion|intygBom'
./gradlew :app:dependencies --configuration runtimeClasspath | grep spring-boot

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Verification commands (after every phase)

./gradlew clean build spotlessCheck test
# If project has integration-test module:
./gradlew :integration-test:integrationTest

Optional: testAggregateTestReport, :app:bootRun with dev profile, SonarQube CI args.

Definition of done: All Jira acceptance criteria met; progress doc complete; properties migrator removed; audit doc (Phase 9) reviewed.

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Phase workflow

Copy this checklist and track in LIFECYCLE-MIGRATION-PROGRESS.md:

- [ ] Phase 0 — Baseline and documentation
- [ ] Phase 1 — Gradle 9 wrapper
- [ ] Phase 2 — intyg-bom + CI images
- [ ] Phase 3 — Spring Boot 4 compile + modular starters
- [ ] Phase 4 — Jackson 3 migration
- [ ] Phase 5 — Autoconfig audit (Redis, JMS, Jackson)
- [ ] Phase 6 — Integration tests + dependency audit
- [ ] Phase 7 — WebClient.Builder + webclient starter
- [ ] Phase 8 — Final sign-off (remove migrator)
- [ ] Phase 9 — Friendliness audit (documentation)

Phase 0 — Baseline

• Add LIFECYCLE-MIGRATION-PLAN.md and LIFECYCLE-MIGRATION-PROGRESS.md
• Record baseline build result, modules, Jackson/Spring touchpoints
• Resolve open questions (Jira ticket, schema bumps, common dep)
• Commit: K1J-XXXX: Add lifecycle migration plan and progress tracking documents

Phase 1 — Gradle 9 wrapper

• Update gradle/wrapper/gradle-wrapper.properties → Gradle 9.6.0
• Fix Gradle 9 breakages (plugins, deprecated APIs)
• Note: Team may do wrapper upgrade manually — agent verifies only
• Commit: K1J-XXXX: Upgrade Gradle wrapper to 9.6.0

Known fix: CycloneDX 3.2.4 + Gradle 9 — replace tasks.matching { … }.configureEach with:

pluginManager.withPlugin('org.cyclonedx.bom') {
    tasks.named('cyclonedxDirectBom').configure { t ->
        t.includeConfigs = ['^runtimeClasspath$']
    }
}

CycloneDX SBOM output (CI pipeline): After Boot 4 + CycloneDX 3.x, cyclonedxBom no longer writes bom.json/bom.xml by default — Spring Boot Gradle plugin reconfigures it to output application.cdx.json (JSON only) for Actuator/JAR embedding. intyg-bom delivers CycloneDX 3.1.0+ (e.g. 3.2.4); the filename change is not from 3.1→3.2.4 but from Spring Boot 3.3+ reacting to the CycloneDX plugin.

Task	Default output (Boot 4 + CycloneDX 3.x)
cyclonedxBom	build/reports/cyclonedx/application.cdx.json
cyclonedxDirectBom	build/reports/cyclonedx-direct/bom.json + bom.xml

If Jenkins/CI expects bom.json and bom.xml from cyclonedxBom (check Jenkins.properties → sbom.aggregation.module), restore legacy paths on the app module (where SBOM is generated):

tasks.named('cyclonedxBom') {
    jsonOutput.set(file("build/reports/cyclonedx/bom.json"))
    xmlOutput.set(file("build/reports/cyclonedx/bom.xml"))
}

Apply only on the module referenced by sbom.aggregation.module (typically app), not on every subproject. Verify :app:cyclonedxBom produces both files after the override.

Phase 2 — intyg-bom + CI images

• gradle.properties: intygBomVersion=1.0.0.16 (or current target)
• Jenkins.properties: builder.image.tag=25.0.3, runtime.image.tag=25.0.1
• Fix build-level breakages only; defer Java source fixes
• Compile may fail on Jackson 2 imports — expected until Phase 4
• Commit: K1J-XXXX: Bump intyg-bom to 1.0.0.16 and update builder/runtime image tags

Phase 3 — Spring Boot 4 compile + starters

Replace raw Spring deps with Boot 4 modular starters (see reference.md):

• spring-boot-starter-web → spring-boot-starter-webmvc
• aspectjweaver → spring-boot-starter-aspectj
• spring-context + spring-jms → spring-boot-starter-jms (where applicable)
• Shared library modules: prefer minimal spring-web over full webmvc starter

Properties (common renames):

• spring.session.redis.* → spring.session.data.redis.*

Temporary: add runtimeOnly(" ") to app module; remove in Phase 8.

Commit: K1J-XXXX: Adapt build and Spring Boot 4 starters for modular dependency layout

Phase 4 — Jackson 3 migration

Imports:

• com.fasterxml.jackson.databind.* → tools.jackson.databind.*
• com.fasterxml.jackson.core.* → tools.jackson.core.*
• com.fasterxml.jackson.datatype.* → tools.jackson.datatype.*
• Keep com.fasterxml.jackson.annotation.*

API changes:

• MappingJackson2MessageConverter → JacksonJsonMessageConverter
• GenericJackson2JsonRedisSerializer → GenericJacksonJsonRedisSerializer
• JsonProcessingException → JacksonException (unchecked)
• Manual construction: JsonMapper.builder().build()
• Prefer injected Boot JsonMapper bean over manual instances
• Remove redundant JavaTimeModule registration where Boot auto-detects

Primitive deserialization: Jackson 3 defaults FAIL_ON_NULL_FOR_PRIMITIVES=true. Prefer wrapper types (Boolean) on DTOs with optional JSON fields. Global JsonMapperBuilderCustomizer is an accepted deviation only when DTO sweep is out of scope — document it.

Also check: Spring Security 7 (OpenSaml5AuthenticationProvider), Testcontainers 2.x (testcontainers-* module prefix).

Commit: K1J-XXXX: Migrate application code and dependencies to Jackson 3

Phase 5 — Autoconfig audit

Area	Anti-pattern	Preferred Boot 4 pattern
Redis cache	@Bean RedisCacheManager	Boot cache auto-config + RedisCacheManagerBuilderCustomizer + @EnableCaching
Jackson	Project-wide customizers	Targeted DTO fixes; JsonMapperBuilderCustomizer only when justified
JMS	Manual everything	Keep manual @Bean when queue name + transacted session + custom converter need isolation; no JmsTemplateCustomizer in Boot 4.1
WebClient	WebClient.builder()	Deferred to Phase 7

Run properties migrator once; apply reported renames only.

Commit: K1J-XXXX: Align manual configuration with Spring Boot 4 autoconfiguration best practices

Phase 6 — Integration tests

• Fix Testcontainers module names (testcontainers-activemq, etc.)
• Session: use spring-boot-starter-session-data-redis (raw spring-session-data-redis insufficient in Boot 4)
• IT HTTP: @AutoConfigureTestRestTemplate + spring-boot-starter-restclient + spring-boot-resttestclient
• Cookie parsing: exact SESSION= match in Set-Cookie, not contains("SESSION")
• RestTestClient migration is optional/deferred if session/cookie issues

Commit: K1J-XXXX: Fix integration tests and complete lifecycle dependency audit

Phase 7 — WebClient auto-config

Critical: WebClient.Builder is not auto-configured by spring-boot-starter-webmvc alone.

• Add spring-boot-starter-webclient to app and modules defining WebClient beans
• Replace spring-boot-starter-webflux with webclient when only HTTP client is needed (no reactive server)
• Refactor @Bean WebClient to inject WebClient.Builder, apply only module filters/customisation, then .build()

Commit: K1J-XXXX: Align integration WebClients with Spring Boot 4 auto-configuration

Phase 8 — Final sign-off

• Full build + tests green
• Remove spring-boot-properties-migrator
• Confirm Java 25, Boot 4.1.0, Gradle 9.6.0, Jackson 3 resolved
• Commit: K1J-XXXX: Complete Java 25 and Spring Boot 4.1 lifecycle migration

Phase 9 — Friendliness audit (documentation)

Create SPRING-BOOT-4-AUDIT.md:

• Map findings to Jira acceptance criteria
• Classify: aligned / accepted deviation / deferred follow-up
• No requirement to implement all follow-ups to close migration

Typical deferred items: RestClient for sync HTTP, RestTestClient ITs, large DTO primitive sweeps.

Commit: K1J-XXXX: Add Spring Boot 4 friendliness audit and Phase 9 documentation

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Test dependency strategy (Boot 4)

There is no spring-boot-starter-junit-test artifact.

Test type	Dependencies
Plain unit tests (Mockito only)	junit-jupiter + mockito-junit-jupiter
Needs ReflectionTestUtils	add spring-test
MVC slice / @WebMvcTest	spring-boot-starter-webmvc-test
Jackson slice	spring-boot-starter-jackson-test
Full stack transitional	spring-boot-starter-test or spring-boot-starter-test-classic

Remove unused starters (e.g. spring-boot-starter-security-test if no @WithMockUser usage).

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Project discovery checklist (run at Phase 0)

Before planning, inventory the target repo:

- [ ] Module layout (app, integration-*, logging, integration-test)
- [ ] Current intygBomVersion, Gradle wrapper, Jenkins image tags
- [ ] Jackson imports count (`com.fasterxml.jackson` excluding annotations)
- [ ] Raw Spring deps (`spring-context`, `spring-webmvc`, `aspectjweaver`, etc.)
- [ ] Manual @Configuration classes (Redis, JMS, WebClient, Security, Session)
- [ ] wsdl2java plugin usage (Gradle 9 compatibility)
- [ ] Apache Camel manual config
- [ ] intyg-common / dependencies.common.version dependency
- [ ] External schema artifacts needing version bumps
- [ ] Testcontainers usage and module names
- [ ] SAML / OpenSaml provider version
- [ ] Jenkins `sbom.aggregation.module` and expected SBOM file paths (`bom.json` vs `application.cdx.json`)

Mark Jira items N/A when not used in the project.

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High-impact pitfalls (from minaintyg)

Pitfall	Symptom	Fix
Missing webclient starter	No qualifying bean of type WebClient.Builder	Add spring-boot-starter-webclient
Raw session-data-redis	IT uses JSESSIONID instead of SESSION	spring-boot-starter-session-data-redis
@Bean RedisCacheManager	Boot cache auto-config disabled	Use RedisCacheManagerBuilderCustomizer
Jackson 3 primitives	Deserialization fails on missing fields	Wrapper types or documented global customizer
IntelliJ duplicate ConnectionFactory	Red underline on JMS config	False positive — Boot conditionals; optional @Qualifier("jmsConnectionFactory")
Boot 4 health probes	Unexpected probe endpoints	Probes enabled by default; property management.endpoint.health.probes.enabled
CycloneDX cyclonedxBom output	CI expects bom.json but gets application.cdx.json	Spring Boot SBOM integration — override jsonOutput/xmlOutput on app module (see Phase 2)
Property typo in prod config	Renaming breaks deploy	Keep typo if externally referenced; document

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Commit message format

K1J-XXXX: [Short imperative summary]

One phase ≈ one commit. Do not commit unless the user asks.

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Document templates

Each migrated project should have:

1. LIFECYCLE-MIGRATION-PLAN.md — phases, inventory, risks, verification
2. LIFECYCLE-MIGRATION-PROGRESS.md — status table, phase log, lessons learned, deferred items
3. SPRING-BOOT-4-AUDIT.md — post-migration friendliness audit (Phase 9)

When migrating intygstjanst or another app: copy structure from minaintyg docs, fill in project-specific inventory and decisions. Use minaintyg as reference implementation, not a verbatim copy.

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Scope boundaries (do not expand without approval)

• RestClient migration (sync HTTP) — separate ticket
• RestTestClient IT migration — separate ticket
• Bulk WebCert/large DTO primitive → wrapper conversion — separate ticket
• wsdl2java / Camel upgrades — only if project uses them
• intyg-bom version authoring — external; only bump consumption version
• Behaviour-changing refactors disguised as migration

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Agent behaviour

1. Read this skill + Spring Boot 4 Migration Guide for unknown APIs
2. Create/update plan and progress docs in Phase 0
3. Execute one phase at a time; verify before proceeding
4. Stop after each phase with commit message suggestion
5. Record lessons learned and accepted deviations in progress doc
6. Ask before schema bumps, common-dep version strategy, or large behavioural changes