AI Agents Migrate a Live Java App: Java 11→25 & Spring Boot 2→4, Fully Autonomous

An Orchestrator agent coordinates a full team of specialized AI sub-agents (Discovery, Planner, Coder, Verifier, Dockerizer) to migrate a real DDD/CQRS Spring Boot RealWorld app from Java 11 → Java 25 and Spring Boot 2.6.3 → 4.1.1 — with zero manually written application code. What you'll see: Discovery agent scanning the codebase, finding 60+ CVEs and a hardcoded JWT secret Planner agent producing a 17-step, dependency-ordered upgrade plan Parallel Coder agents racing through javax→jakarta migration, Spring Security's removed WebSecurityConfigurerAdapter, JJWT API changes, and MyBatis upgrades A staged Boot 2→3→4 upgrade (not a risky direct jump) The hardest part: swapping Netflix DGS for the Boot-4-native GraphQL starter Real bugs found and fixed live: a Jackson 3 namespace break, a Spring Security filter double-registration causing every request to 401, and a Flyway auto-configuration module split that silently broke schema migrations A Verifier agent independently confirming 68/68 tests green and CVEs remediated Final Dockerization of the modernized app Tech stack before/after: Java 11 → Java 25 (LTS) Spring Boot 2.6.3 → 4.1.1 Gradle 7.4 → 9.7.1 Netflix DGS 4.9.21 → graphql-dgs-spring-graphql-starter 12.0.1 Jackson 2 → Jackson 3 MyBatis Starter 2.2.2 → 4.1.0, Flyway 8.0.5 → 12.4.0 Chapters 0:00 Intro — the goal: Java 11→25, Spring Boot 2→4 1:52 Prerequisites check (jabba, Gradle, repo state) 16:25 Discovery Agent — full stack assessment, CVEs, hidden JWT secret 23:07 Phase 0 — Java 25 + Gradle 9.7.1 (isolated) 30:40 Phase 1 — Boot 3.5 intermediate stop begins 36:55 Parallel Coders — jakarta namespace, MyBatis, JJWT 43:45 Phase 1 checkpoint — 68/68 tests green on Boot 3.5 53:00 Phase 2 — Boot 4.1.1 upgrade begins 60:50 Phase 3 — JWT secret rotation, log leak fix, CI update 70:00 Verifier Agent — final CVE & regression report