Microprofile Server

Composition

• compose with java-conventions for all language-level Java rules (syntax, style, naming, visibility, interfaces/classes, methods/lambdas, streams/collections, exceptions, comments/JavaDoc)
• this skill specializes only the MicroProfile / Jakarta EE server context — it does not restate language-level rules

Dependencies

• prefer dependencies in this order: Java SE, MicroProfile, Jakarta EE

Exceptions (JAX-RS)

• in JAX-RS projects, inherit from WebApplicationException for custom exceptions
• use explicit exceptions like BadRequestException for Response.Status.BAD_REQUEST
• throw explicit WebApplicationException subclasses (e.g. BadRequestException, NotFoundException) rather than constructing Response objects inline — they are automatically mapped to the correct HTTP status by the JAX-RS runtime

BCE/ECB Architecture

• structure code using the Boundary Control Entity (BCE/ECB) pattern
• package structure: [ORGANIZATION_NAME].[PROJECT_NAME].[COMPONENT_NAME].[boundary|control|entity]
• top level package reflects the application responsibility or name
• suggest renaming the top level [PROJECT_NAME] package when it does not reflect the project's name or responsibility
• business components are children of top level package, named after their responsibilities
• a BC may represent a domain concept or a shared concern; both are valid when the responsibility has a name and is reused across the application
• boundary, control, entity packages are only allowed in business components
• a BC does not need every layer; a BC may consist of only a control layer when its responsibility is procedural and consumed by other BCs
• not every BCE component needs a dedicated boundary package; control package contents can be accessed directly
• prefer a dedicated BC over the root application package when a shared concern carries domain or protocol semantics, exposes more than one operation, or is expected to grow
• reserve the root application package for trivial single-class plumbing with no business semantics and no protocol coupling
• do not explain the BCE pattern in documentation

Boundary Layer

• keep coarse-grained classes in the boundary package
• place facades in the boundary package
• health checks must be placed in the boundary package
• @Transactional is only allowed in boundary layer
• if there is no Boundary stereotype, use ApplicationScope instead

Control Layer

• implement procedural business logic in the control package

Entity Layer

• maintain domain objects, data classes, and entities in the entity package
• entities maintain state and corresponding behavior
• model value objects as enums
• direct references between entities from independent BCs are allowed, but always aim for Maximal Cohesion and Minimal Coupling between BCs
• if a relation exists in the database (e.g. JPA foreign key), the entities must carry a corresponding reference (id field or association); the DB schema is the source of truth
• excessive cross-BC references or shared configuration is a refactoring signal — split, merge, or rebalance the BCs to restore cohesion

Components

• create new components with minimal business logic and essential fields only

JavaDoc (MicroProfile/Jakarta EE)

• follow links in JavaDoc to external specifications and use them for code generation
• use popular, also funny, technical terms from the Java SE, MicroProfile and Jakarta EE ecosystems as examples in unit tests and javadoc

README Guidelines

• write brief, 'to the point' README.md files for advanced developers
• use precise and concise language; avoid generic adjectives like "simple", "lightweight"
• do not include detailed project structure (file/folder listings); high-level module descriptions are acceptable
• never list REST resources in READMEs
• if modules are listed, provide links
• do not use "Orchestrates" term; use more specific alternatives

Integration Tests

• integration tests end with IT suffix and are executed by the failsafe maven plugin (no configuration necessary)

System Tests (ST)

• system tests are created in a dedicated Maven module ending with "-st"
• use microprofile-rest-client for testing JAX-RS resources
• REST client interfaces: src/main/java of the -st module
• test classes: src/test/java of the -st module
• name client interfaces after the resource with "Client" suffix (e.g., GreetingsResource -> GreetingsResourceClient)
• RegisterRestClient configKey: "service_uri"
• STs end with "IT" suffix
• do not use RestAssured. Write e2e test in the -st module
• execute system tests after every major change to the service module
• in PoC mode (user-activated), system test execution is skipped

JAX-RS

• resources should be named in plural (e.g., SpeakersResource not SpeakerResource)
• @Consumes and @Produces should be declared on class-level
• do not implement business logic in JAX-RS resources; delegate instead
• prefer returning JAX-RS Response over JsonObject in resources
• do not create new "@RegisterRestClient(configKey," - reuse existing

JSON Serialization (JSON-P)

• prefer JSON-P over JSON-B
• record entities should ship with toJSON method returning a JSON-P object
• always map JSON-P in the boundary to entities
• create record entities from JSON-P JsonObject in static method: fromJSON(JsonObject json)

Project Management

• always ask before changing pom.xml
• on opening existing projects, load AGENTS.md (if present) before making changes
• do not create or change any files on opening existing projects; stop after initialization and wait for instructions
• do not generate code initially in an empty project
• Maven pom.xml must not be created for Java 25 CLI applications
• never use quarkus-hibernate-validator
• create metrics and observability features with OTEL / opentelemetry