133 lines
5.9 KiB
Markdown
133 lines
5.9 KiB
Markdown
# Spring Boot Version
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**Status:**
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- proposed: 2026-06-09
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- accepted: -
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- rejected: -
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- superseded: -
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**Decision [proposed]:** Spring Boot 4.0 — only actively-supported version; springmockk workaround via @TestConfiguration until a compatible release is published.
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## Context and Problem Statement
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GitTally is a greenfield Kotlin/Spring Boot project.
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A Spring Boot version must be chosen for the initial setup.
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The choice is constrained by the support lifecycle: as of June 2026,
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almost the entire Spring Boot 3.x release train is already end-of-life.
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### Technical Background
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[Spring Boot support lifecycle](https://endoflife.date/spring-boot)
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([HeroDevs April 2026 overview](https://www.herodevs.com/blog-posts/spring-boot-versions-eol-dates-and-latest-releases-april-2026))
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as of June 2026:
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| Version | EOL date | Status |
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|---------|----------------|---------------------------------|
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| 3.5.x | June 30, 2026 | Expires this month |
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| 4.0.x | December 2026 | **Active** (current: 4.0.6) |
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Spring Boot 3.5.x is the final 3.x release; there will be no 3.6.
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The Spring project ended the 3.x train at 3.5 and continues in the 4.x line
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([Spring Boot milestones](https://github.com/spring-projects/spring-boot/milestones)).
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Spring Boot 4.0 moves to Spring Framework 7 and Jakarta EE 11.
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The key ecosystem dependencies and their Spring Boot 4.0 compatibility status:
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| Dependency | Role | Spring Boot 4.0 status |
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|---|---|---|
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| [picocli-spring-boot-starter](https://picocli.info/) | CLI wiring | Untested; last documented target is Spring Boot 3.1. The integration is minimal (one `IFactory` bean), so it likely works in practice. |
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| [springmockk](https://github.com/Ninja-Squad/springmockk) | `@MockkBean` in tests | **Incompatible** — confirmed Spring Boot 3.x only. |
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| [kotest-extensions-spring](https://github.com/kotest/kotest-extensions-spring) | Kotest + `@SpringBootTest` | Compatibility unconfirmed. |
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| [wiremock-spring-boot](https://wiremock.org/docs/spring-boot/) | HTTP stubbing in tests | **Compatible** — Spring Boot 4.0 explicitly supported since January 2026. |
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## Considered Options
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* Spring Boot 3.5.x (latest 3.x)
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* Spring Boot 4.0.x
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### Spring Boot 3.5.x
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The last actively-supported 3.x release.
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#### Advantages
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- Full compatibility with all current dependencies
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(picocli-spring-boot-starter, springmockk, kotest-extensions-spring).
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- Well-known ecosystem; documentation and community resources are mature.
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#### Disadvantages
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- EOL June 30, 2026 — expires this month.
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Starting a project on a version ending within days is indefensible.
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- Upgrading to Spring Boot 4.0 immediately after project start incurs migration cost
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at the worst possible time (early, before the codebase is stable).
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### [Spring Boot 4.0](https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-4.0-Release-Notes)
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The current and only actively-supported major release.
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#### Advantages
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- The only version receiving security patches and updates beyond June 2026.
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- Spring Framework 7 and Jakarta EE 11: active, long-term foundation.
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- Aligns with Gradle 9 when that upgrade is eventually made (ADR 0002).
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- Wiremock Spring Boot integration fully supports it.
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#### Disadvantages
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- **springmockk is incompatible.** The `@MockkBean` / `@SpykBean` annotations are not available.
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This matters in particular for `@WebMvcTest` (controller error-behaviour) and
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`@DataJpaTest`-adjacent tests where collaborators need to be mocked in the Spring context.
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The workaround is to register MockK mocks as Spring beans via `@TestConfiguration`,
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which preserves full MockK syntax (`every { }`, `verify { }`) at the cost of one
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inner configuration class per test file and an explicit `clearMocks()` call in `beforeEach`:
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```kotlin
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@WebMvcTest(SomeController::class)
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@Import(SomeControllerTest.Mocks::class)
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class SomeControllerTest : FunSpec() {
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@TestConfiguration
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class Mocks {
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@Bean fun someService(): SomeService = mockk()
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}
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@Autowired lateinit var someService: SomeService
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init {
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beforeEach { clearMocks(someService) }
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// full MockK syntax available
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}
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}
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```
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This is more verbose than `@MockkBean` but avoids mixing Mockito and MockK.
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Revisit once springmockk publishes a Spring Boot 4.0-compatible release.
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- **picocli-spring-boot-starter is untested against Spring Boot 4.0.**
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The risk is low (the auto-configuration is a single `IFactory` bean with no framework-version-specific API),
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but it cannot be assumed safe until verified by a running context test.
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- **kotest-extensions-spring** compatibility needs verification before the first
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`@SpringBootTest` test is written.
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- Relatively new GA; fewer community examples for the 4.0 generation.
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## Decision Outcome
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**Spring Boot 4.0** is chosen.
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The main reasons:
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- Spring Boot 3.5.x expires this month; starting on it is not a viable option.
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- Spring Boot 4.0 is the only release with active support through the foreseeable project lifetime.
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- The ecosystem blockers are manageable:
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- picocli-spring-boot-starter risk is low and will be confirmed by the existing
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context-wiring smoke test (`ApplicationContextTest`).
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- springmockk is a test-only dependency; the short-term workaround
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(`@TestConfiguration` with `mockk()` beans, `clearMocks()` in `beforeEach`)
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preserves full MockK syntax in `@WebMvcTest` and `@DataJpaTest` tests
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without falling back to Mockito.
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- kotest-extensions-spring compatibility must be verified before the
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first `@SpringBootTest` test is written.
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Open items before the code is upgraded:
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1. Bump Spring Boot to 4.0.6 and verify `ApplicationContextTest` still passes.
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2. Confirm picocli-spring-boot-starter works under the new context.
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3. Confirm kotest-extensions-spring works with Spring Boot 4.0.
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4. Replace `@MockkBean` usages with the `@TestConfiguration` + `mockk()` pattern
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until springmockk publishes a compatible release.
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