---
titel: "Modernizing a legacy Java codebase"
adresse: https://anvil-coder.tech/en/use-cases/legacy-java-modernisieren
beschreibung: "A grown Spring project on an outdated Java and framework version is broken into checkable slices and moved step by step to a defined target level."
sprache: en
---

Use cases

# Modernizing a legacy Java codebase

A grown Spring project on an outdated Java and framework version is broken into checkable slices and moved step by step to a defined target level.

## Case study in full

Synthetic example — illustrative magnitudes, not a measurement.

Stack profile: `java-spring-boot-4-hexagonal` · Data origin: Synthetic example, not a reference run. · Measurement period: —

A grown Spring project runs on an outdated Java and framework version. Dependencies have accumulated over years, part of the test suite is red or skipped, and migrating to a defined target level was repeatedly postponed because it did not break down into small, checkable steps.

**Out of scope — not automated:** Not automated: which target level is pursued remains a project decision made in advance. Review of every single slice, approval of critical dependency changes, and the final merge decision remain with a human throughout.

### Prerequisites

- Repository with an existing build configuration (Gradle/Maven) and a runnable test suite as the starting point.

- A stack profile naming the target version and architecture conventions.

- Guardrails that record the project's binding conventions.

- Approval of the ticket backlog by a project member before the first run.

### Workflow

- A ticket in the connected tracker describes the target level per module.

- The plan breaks the migration into ordered, individually checkable slices.

- Each slice changes one bounded portion: a dependency, an API adjustment, or a test fix.

- Validation per slice: compilation, affected tests, static analysis.

- The result goes out as a pull request to the repository — review and merge remain with a human.

### Result artifacts

- Changed files and dependencies per slice, traceable in the commit history.

- Test results and gate status documented per slice.

- One pull request per slice or bundled, referencing the ticket.

- Points left open are recorded as separate backlog tickets, not silently dropped.

### Key figures

Scope

**Stories/tickets**

1

**Slices**

34

**Files/modules**

118

Throughput

**Validated slices**

31

**Retries**

9

**Human approvals**

6

Quality

**Checks run**

Compile, Unit Tests, Static Analysis

**Gates passed**

5

**Gates failed**

1

**Remaining debt**

Two older test classes do not yet cover the new code path; deferred as a ticket rather than silently removed.

Resources — no pricing

**Prompt tokens**

500000

**Completion tokens**

200000

**Cache tokens**

750000

**Model calls**

200

**Sandbox runtime**

90 minutes

**Model/stack context**

Java 17 → Java 25, Spring Boot 3 → Spring Boot 4 (target profile java-spring-boot-4-hexagonal).

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Every example on this page was created for illustration. It is not a promise about the duration, quality or cost of a future run of your own — your own figures appear in the cockpit after logging in, within your own tenant context.

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