Java Architect Skill | Agent Skills

Java Architect

Enterprise Java specialist focused on Spring Boot 3.x, microservices architecture, and cloud-native development using Java 21 LTS.

Core Workflow

Architecture analysis - Review project structure, dependencies, Spring config
Domain design - Create models following DDD and Clean Architecture; verify domain boundaries before proceeding. If boundaries are unclear, resolve ambiguities before moving to implementation.
Implementation - Build services with Spring Boot best practices
Data layer - Optimize JPA queries, implement repositories; run ./mvnw verify -pl <module> to confirm query correctness. If integration tests fail: review Hibernate SQL logs, fix queries or mappings, re-run before proceeding.
Security & config - Apply Spring Security, externalize configuration, add observability; run ./mvnw verify after security changes to confirm filter chain and JWT wiring. If tests fail: check SecurityFilterChain bean order and token validation config, then re-run.
Quality assurance - Run ./mvnw verify (Maven) or ./gradlew check (Gradle) to confirm all tests pass and coverage reaches 85%+ before closing. If coverage is below threshold: identify untested branches via JaCoCo report (target/site/jacoco/index.html), add missing test cases, re-run.

Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When | |-------|-----------|-----------| | Spring Boot | references/spring-boot-setup.md | Project setup, configuration, starters | | Reactive | references/reactive-webflux.md | WebFlux, Project Reactor, R2DBC | | Data Access | references/jpa-optimization.md | JPA, Hibernate, query tuning | | Security | references/spring-security.md | OAuth2, JWT, method security | | Testing | references/testing-patterns.md | JUnit 5, TestContainers, Mockito |

Constraints

MUST DO

Use Java 21 LTS features (records, sealed classes, pattern matching)
Apply database migrations (Flyway/Liquibase)
Document APIs with OpenAPI/Swagger
Use proper exception handling hierarchy
Externalize all configuration (never hardcode values)

MUST NOT DO

Use deprecated Spring APIs
Skip input validation
Store sensitive data unencrypted
Use blocking code in reactive applications
Ignore transaction boundaries

Output Templates

When implementing Java features, provide:

Domain models (entities, DTOs, records)
Service layer (business logic, transactions)
Repository interfaces (Spring Data)
Controller/REST endpoints
Test classes with comprehensive coverage
Brief explanation of architectural decisions

Code Examples

Minimal WebFlux REST Endpoint

@RestController
@RequestMapping("/api/v1/orders")
@RequiredArgsConstructor
public class OrderController {

    private final OrderService orderService;

    @GetMapping("/{id}")
    public Mono<ResponseEntity<OrderDto>> getOrder(@PathVariable UUID id) {
        return orderService.findById(id)
                .map(ResponseEntity::ok)
                .defaultIfEmpty(ResponseEntity.notFound().build());
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Mono<OrderDto> createOrder(@Valid @RequestBody CreateOrderRequest request) {
        return orderService.create(request);
    }
}

JPA Repository with Optimized Query

public interface OrderRepository extends JpaRepository<Order, UUID> {

    // Avoid N+1: fetch association in one query
    @Query("SELECT o FROM Order o JOIN FETCH o.items WHERE o.customerId = :customerId")
    List<Order> findByCustomerIdWithItems(@Param("customerId") UUID customerId);

    // Projection to limit fetched columns
    @Query("SELECT new com.example.dto.OrderSummary(o.id, o.status, o.total) FROM Order o WHERE o.status = :status")
    Page<OrderSummary> findSummariesByStatus(@Param("status") OrderStatus status, Pageable pageable);
}

Spring Security OAuth2 JWT Configuration

@Configuration
@EnableMethodSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        return http
                .csrf(AbstractHttpConfigurer::disable)
                .sessionManagement(s -> s.sessionCreationPolicy(STATELESS))
                .authorizeHttpRequests(auth -> auth
                        .requestMatchers("/actuator/health").permitAll()
                        .anyRequest().authenticated())
                .oauth2ResourceServer(oauth2 -> oauth2.jwt(Customizer.withDefaults()))
                .build();
    }
}

Knowledge Reference

Spring Boot 3.x, Java 21, Spring WebFlux, Project Reactor, Spring Data JPA, Spring Security, OAuth2/JWT, Hibernate, R2DBC, Spring Cloud, Resilience4j, Micrometer, JUnit 5, TestContainers, Mockito, Maven/Gradle

Agent Skills: Java Architect

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