This repository contains a Codex/Claude skill for designing and implementing Java systems with Domain-Driven Design.

The skill is intended for tasks such as:

• Java backend architecture with bounded contexts
• aggregate and value object modeling
• Spring Boot service design with clear layer boundaries
• anti-corruption layer design
• shared kernel and published contracts decisions
• query-side/read-model design
• saga and eventual consistency workflows
• modular monolith or multi-module project structure

The skill lives in:

java-domain-driven-design/

Key files:

• java-domain-driven-design/SKILL.md
• java-domain-driven-design/agents/openai.yaml
• java-domain-driven-design/references/*.md

The skill defines guidance for:

• strategic design: bounded contexts, context relationships, ownership
• tactical design: entities, value objects, aggregates, repositories, domain services, domain events
• layering: domain, application, infrastructure, interfaces
• anti-corruption layers for foreign models
• assemblers for boundary-local type conversion
• shared kernel versus contracts
• query side versus write side
• transaction boundaries, eventual consistency, sagas
• testing strategy and error handling
• Maven and Gradle multi-module layouts

• Keep domain language and business invariants at the center.
• Protect bounded contexts from foreign models with ACLs.
• Keep shared-kernel thin and stable.
• Keep contracts separate from local domain models.
• Keep assemblers pure and close to the boundary they serve.
• Keep read models separate from write-side aggregate concerns when needed.
• Keep strong consistency inside aggregate boundaries and use events or sagas across boundaries.

For medium or large systems, the skill recommends:

• shared-kernel
• optional contracts
• one module per bounded context
• one app or bootstrap module

Both Maven and Gradle examples are documented in:

• java-domain-driven-design/references/build-structures.md

Example prompt:

Use $java-domain-driven-design to design a Java modular monolith for order, inventory, and payment management with bounded contexts, aggregates, ACLs, contracts, query models, and a Spring Boot app module.

You can also use it for smaller requests, for example:

Use $java-domain-driven-design to refactor this Spring Boot order service into proper aggregates, application services, repository ports, persistence adapters, and request/response assemblers.

The skill has been validated with the skill validator and is currently in a valid state.

This repository is licensed under the MIT License. See LICENSE.

This repository now includes a user-facing README.md for navigation, but the skill itself is driven by:

• SKILL.md for model instructions
• agents/openai.yaml for invocation metadata
• references/ for progressive disclosure