| name | 123-java-design-patterns |
| description | Use when you need to select, review, or implement Java design and integration patterns — including classic Java design patterns, REST API patterns, Kafka and event-driven patterns, database and persistence patterns, and cross-cutting integration patterns. This should trigger for requests such as Apply Java design patterns; Review REST API patterns; Design Kafka event-driven patterns; Improve database persistence patterns; Add resilient integration patterns. Part of Plinth Toolkit |
| license | Apache-2.0 |
| metadata | {"author":"Juan Antonio Breña Moral","version":"0.18.0"} |
Java Design and Integration Patterns
Guide Java developers in selecting patterns by problem signal, implementation context, and trade-off rather than by pattern name alone.
What is covered in this Skill?
- Classic Java design patterns for application code: creational, structural, and behavioral patterns
- REST API patterns for resource design, contracts, idempotency, versioning, and error handling
- Kafka and event-driven patterns for event schemas, partitioning, idempotency, retries, outbox, and sagas
- Database and persistence patterns for repositories, transactions, aggregates, locking, migrations, and read models
- Cross-cutting integration patterns for anti-corruption layers, resilience, observability, and reliable message boundaries
Scope: Use this skill to explain, review, and implement practical patterns in Java systems. Prefer simple code first; introduce a pattern only when it reduces real complexity, protects a boundary, improves testability, or makes change safer.
Constraints
Pattern guidance must be problem-led, concrete, and safe to apply in Java projects.
- PROBLEM FIRST: Identify the design pressure before naming or applying a pattern
- NO PATTERN SHOPPING: Do not add abstractions only because a pattern exists; prefer simple code when variation is not present
- BUILD SAFETY: For code changes, run
./mvnw compile or mvn compile before refactoring and ./mvnw clean verify or mvn clean verify after changes
- REFERENCE SELECTION: Read the relevant reference before acting: Java code patterns, REST API patterns, Kafka/event-driven patterns, database/persistence patterns, or cross-cutting integration patterns
- TRADE-OFFS REQUIRED: Explain the benefit, cost, and when-not-to-use guidance for any recommended pattern
When to use this skill
- Apply Java design patterns
- Review Java code for design patterns
- Choose REST API patterns
- Design Kafka event-driven patterns
- Improve database persistence patterns
- Add resilient integration patterns
Workflow
- Identify the design pressure
Clarify the concrete problem: object creation, behavior variation, API contract evolution, event delivery, persistence consistency, integration reliability, or another recurring design force.
- Select the relevant reference
Read only the matching reference(s): references/123-java-design-patterns.md, references/123-rest-api-patterns.md, references/123-kafka-event-driven-patterns.md, references/123-database-persistence-patterns.md, or references/123-cross-cutting-integration-patterns.md.
- Recommend the smallest useful pattern
Choose the simplest pattern that addresses the design pressure. Show how it changes responsibilities, boundaries, tests, operations, or evolution safety.
- Implement or document the pattern
When code changes are requested, make focused Java or configuration changes following the project conventions. When design advice is requested, provide diagrams, examples, request/response shapes, event shapes, or transaction flows as appropriate.
- Validate the outcome
Verify that the resulting design remains understandable, testable, and operationally safe. Run the project build for code changes and name any remaining trade-offs.
Reference
For detailed guidance, examples, and constraints, see:
