| name | migrate-spring-to-quarkus |
| description | Migrates Spring Boot applications to Quarkus using a modular, gate-driven approach. Supports Spring compatibility extensions and native Quarkus migration paths. Use when the user wants to migrate, convert, or port a Spring Boot app to Quarkus, mentions "spring to quarkus", "quarkus migration", "replace spring", or asks about migrating "pom.xml", "build.gradle", "Spring MVC", "Spring Data JPA", "Thymeleaf", "@SpringBootApplication". |
| license | Apache-2.0 |
| metadata | {"author":"Quarkus Community - https://github.com/quarkusio/quarkus"} |
Spring Boot to Quarkus Migration
Modular, gate-driven migration of Spring Boot applications to Quarkus.
Critical Rules
- Never delete code you cannot migrate. If you cannot fully migrate a piece of code, leave the original in place with a
// TODO: Migration required — <reason> comment explaining what needs to change and why. This applies to:
- Methods, classes, or annotations you don't know how to convert
- Spring-specific patterns without a clear Quarkus equivalent
- Configuration or wiring code whose purpose is unclear
If you must remove code (e.g., a Spring-only base class), document what was removed and why in a
// REMOVED: comment at the same location.
- Don't break the build. Run the compile command after each phase (
./mvnw clean compile -DskipTests for Maven, ./gradlew clean compileJava -x test for Gradle). Never move to the next phase with a broken build.
- Document every decision. When choosing between migration approaches, explain the trade-off to the user.
- No silent changes. Every file modification must be intentional and traceable. If a check fails after a phase, diagnose and fix — don't skip the check or delete the failing code.
Reference Files
Load the relevant reference file when working on a module:
Step 1: Analyze & Choose Strategy
Scan the application to understand what needs to migrate:
- Build system: Read the build file (
pom.xml for Maven, build.gradle or build.gradle.kts for Gradle) — Spring Boot version, starters, plugins
- Java code: Search for Spring annotations (DI, REST, Data, Security, Scheduling)
- Configuration: Read
application.properties/application.yml, check for profiles
- UI / View layer: Check for Thymeleaf/JSP templates, static resources, Model+View patterns
- Tests: Check for
@SpringBootTest, @WebMvcTest, @DataJpaTest
Present a summary table with area, findings, and complexity. Then ask the user to choose a strategy:
- Spring compatibility (recommended): Use
quarkus-spring-web, quarkus-spring-data-jpa, etc. Minimal code changes.
- Native Quarkus: Replace all Spring annotations with JAX-RS/CDI. More work, full Quarkus experience.
Stop here and wait for the user's response before continuing. Do not ask about git workflow or anything else in the same message.
Step 2: Git branch (optional)
After the user has chosen a strategy, check if the target project is a git repository. If it is, propose the git workflow:
Migration workflow: Each migration run can be isolated in its own branch (migration/run-01, migration/run-02, ...) created from main. The branch will contain a single commit with all changes plus a migration report. A draft PR against main will be created for review — it is never merged, it serves as a permanent diff and discussion record. Would you like to use this workflow?
- User accepts → follow modules/git.md — Pre-migration section. Propose the branch name and wait for confirmation before creating it.
- User declines → skip git management entirely, proceed with migration in the current branch.
- Not a git repo → inform the user, skip git management, proceed normally.
Step 3: Execute Modules
Decision Gate Table
For each module, evaluate whether it applies to this project. A module executes only when its gate is PASS.
Inspect the project to determine the gate result — do not rely on blind grep commands; use your understanding of the codebase.
| Module | Gate Check | Gate Result |
|---|
| jdk | JDK 21+ required | ALWAYS -- stop migration if < 21 |
| build | Spring Boot parent/starters/spring-boot-maven-plugin in pom.xml, or Spring Boot/io.spring.dependency-management plugins in build.gradle(.kts) | PASS if Spring Boot build markers found; SKIP otherwise |
| code | Spring annotations in Java sources (@Component, @Service, @Controller, @Repository, @Entity, @Autowired, etc.) | PASS if Spring annotations found; SKIP otherwise |
| frontend | Thymeleaf/JSP templates in templates/ or static resources in static/ | PASS if view layer found; SKIP otherwise |
| testing | Spring test annotations in test sources (@SpringBootTest, @WebMvcTest, @MockBean) | PASS if Spring tests found; SKIP otherwise |
| cleanup | Leftover Spring artifacts after all other modules | ALWAYS — runs after all other modules |
Execution Protocol
FOR module IN [build, code, frontend, testing, cleanup]:
1. EVALUATE — inspect the project for the gate condition
2. DECIDE
IF gate == ALWAYS → proceed to step 3
IF gate == PASS → proceed to step 3
IF gate == SKIP → log "Module {name}: SKIPPED — {reason}", mark checkbox, continue
3. LOAD — read the module file and relevant reference files
4. EXECUTE — follow the module instructions, adapting to the chosen strategy
5. COMPILE — run the project's compile command (`./mvnw clean compile -DskipTests` for Maven, `./gradlew clean compileJava -x test` for Gradle)
Fails → diagnose and fix before proceeding
6. LOG — mark checkbox as done
Running Individual Modules
To run a single module outside the full migration flow, read its file directly:
- "Read
modules/build.md and execute it"
- "Run only the frontend module"
- "Re-run the cleanup module"
The module will use the current project state and the chosen strategy (if already decided). If no strategy has been chosen, the module will ask.
Step 4: Verify the Migration
Run each check in order. A check fails = stop and fix before continuing.
| # | Check | Command (Maven / Gradle) | Pass criteria |
|---|
| 1 | Builds | ./mvnw clean package -DskipTests / ./gradlew clean build -x test | Exit code 0, no compilation errors |
| 2 | No Spring deps | Search build file for org.springframework | Zero Spring deps (except Spring compat extensions if using that strategy) |
| 3 | Has Quarkus | Search build file for io.quarkus | Quarkus BOM and at least one extension present |
| 4 | Tests pass | ./mvnw test / ./gradlew test | All tests pass using @QuarkusTest |
| 5 | Starts up | ./mvnw quarkus:dev / ./gradlew quarkusDev | App starts, curl http://localhost:8080/q/health returns UP |
| 6 | No leftover templates | Search for Thymeleaf/JSP references | None remaining (unless intentionally kept) |
Step 5: Migration Review (Self-Reflection)
Answer each question honestly:
- What migrated cleanly? Patterns that mapped 1:1.
- What required manual judgment? Non-obvious decisions made.
- What was left as TODO? Every
// TODO: Migration required comment and why.
- Was any code removed? What, where, justification. Flag runtime risks.
- What checks failed initially? Failures from Step 4 and how you fixed them.
- What's missing from the skill references? Mappings you had to figure out.
Migration Report
Present the review as a structured report:
## Migration Report: [app-name]
### Summary
- Strategy: [Full Migration / Spring Compatibility]
- Agent: [AI agent name - e.g claude, pi, opencode, gemini, etc]
- Model: [model name — e.g. claude-sonnet-4-6, check system context]
- Modules completed: [X/4]
- Checks passed: [X/6]
- Token usage: [input tokens / output tokens — check session stats]
- Estimated cost: [~$X.XX — token counts × per-model pricing from anthropic.com/pricing]
### Changes by Module
| Module | Files changed | Key changes |
|--------|--------------|-------------|
| build | pom.xml or build.gradle(.kts), application.properties | ... |
| code | ... | ... |
| frontend | ... | ... |
| testing | ... | ... |
### Validation Results
| Check | Result | Notes |
|-------|--------|-------|
| Builds | PASS/FAIL | |
| No Spring deps | PASS/FAIL | |
| Has Quarkus | PASS/FAIL | |
| Tests pass | PASS/FAIL | |
| Starts up | PASS/FAIL | |
| No leftover templates | PASS/FAIL | |
### Unmigrated Code (TODOs)
| File | Line | What | Why not migrated |
|------|------|------|-----------------|
### Removed Code
| File | What was removed | Justification |
|------|-----------------|---------------|
### Skill Improvement Suggestions
- [Any missing mappings, unclear instructions, or edge cases discovered]
Step 6: Commit and PR (only if git workflow was accepted)
Follow modules/git.md — Post-migration section. Ask the user for confirmation before committing, and again before pushing / creating the draft PR. Do not proceed with either action without explicit user approval.
