spring-boot

name spring-boot description Spring Boot 3.x development - REST APIs, JPA, Security, Testing, and Cloud-native patterns. Use for building enterprise Java applications with Spring Boot. metadata {"version":"2.0.0","domain":"backend","triggers":"Spring Boot, Spring Framework, Spring Security, Spring Data JPA, Spring WebFlux, Java REST API, Microservices Java","role":"specialist","scope":"implementation","output-format":"code"} Spring Boot Skill Enterprise Spring Boot 3.x development with focus on clean architecture and production-ready code. Core Workflow Analyze - Understand requirements, identify service boundaries, APIs, data models Design - Plan architecture, confirm design before coding Implement - Build with constructor injection and layered architecture Secure - Add Spring Security, OAuth2, method security; verify tests pass Test - Write unit, integration tests; run ./mvnw test and confirm all pass Deploy - Configure health checks via Actuator; validate /actuator/health returns UP Quick Start Templates Entity @Entity @Table(name = "products") public class Product { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @NotBlank private String name; @DecimalMin("0.0") private BigDecimal price; // Getters/Setters (no Lombok) } Repository public interface ProductRepository extends JpaRepository <Product, Long> { List<Product> findByNameContainingIgnoreCase (String name) ; } Service @Service @Transactional(readOnly = true) public class ProductService { private final ProductRepository repo; public ProductService (ProductRepository repo) { this .repo = repo; } public List<Product> search (String name) { return repo.findByNameContainingIgnoreCase(name); } @Transactional public Product create (ProductRequest request) { var product = new Product (); product.setName(request.name()); product.setPrice(request.price()); return repo.save(product); } } REST Controller @RestController @RequestMapping("/api/v1/products") @Validated public class ProductController { private final ProductService service; public ProductController (ProductService service) { this .service = service; } @GetMapping public List<Product> search ( @RequestParam(defaultValue = "") String name) { return service.search(name); } @PostMapping @ResponseStatus(HttpStatus.CREATED) public Product create ( @Valid @RequestBody ProductRequest request) { return service.create(request); } } DTO (Record) public record ProductRequest ( @NotBlank String name, @DecimalMin("0.0") BigDecimal price ) {} Global Exception Handler @RestControllerAdvice public class GlobalExceptionHandler { @ExceptionHandler(MethodArgumentNotValidException.class) @ResponseStatus(HttpStatus.BAD_REQUEST) public Map<String, String> handleValidation (MethodArgumentNotValidException ex) { return ex.getBindingResult().getFieldErrors().stream() .collect(Collectors.toMap(FieldError::getField, error -> error.getDefaultMessage() != null ? error.getDefaultMessage() : "Invalid" )); } @ExceptionHandler(EntityNotFoundException.class) @ResponseStatus(HttpStatus.NOT_FOUND) public Map<String, String> handleNotFound (EntityNotFoundException ex) { return Map.of( "error" , ex.getMessage()); } } Test Slice @WebMvcTest(ProductController.class) class ProductControllerTest { @Autowired MockMvc mockMvc; @MockBean ProductService service; @Test void createProduct_validRequest_returns201 () throws Exception { var product = new Product (); product.setName( "Widget" ); when (service.create(any())).thenReturn(product); mockMvc.perform(post( "/api/v1/products" ) .contentType(MediaType.APPLICATION_JSON) .content( """{"name":"Widget","price":10.0}""" )) .andExpect(status().isCreated()) .andExpect(jsonPath( "$.name" ).value( "Widget" )); } } Reference Guide Load detailed patterns based on context: Topic Reference When to Load Web/REST references/web.md Controllers, validation, exception handling Data Access references/data.md JPA, repositories, transactions, queries Security references/security.md Spring Security 6, OAuth2, JWT, auth Cloud/Config references/cloud.md Config server, discovery, resilience Testing references/testing.md Unit, integration, slice tests Constraints MUST DO Constructor injection (no field injection) @Valid on all request bodies @Transactional for multi-step writes @Transactional(readOnly = true) for reads Type-safe config with @ConfigurationProperties Global exception handling with @RestControllerAdvice Externalize secrets (use env vars, not properties files) MUST NOT DO Field injection ( @Autowired on fields) Skip input validation on endpoints Mix blocking and reactive code Store secrets in application.properties Use deprecated Spring Boot 2.x patterns Hardcode URLs, credentials, environment values Architecture Patterns Project Structure: src/main/java/pl/piomin/services/ ├── controller/ # REST endpoints ├── service/ # Business logic ├── repository/ # Data access ├── model/ # Entities ├── dto/ # Request/Response DTOs ├── config/ # Configuration └── exception/ # Custom exceptions + handler Layering: Controller → Service → Repository Controller handles HTTP, validation Service handles business logic, transactions Repository handles data persistence Clean Architecture Principles: Domain models independent of frameworks Use case driven design Dependency inversion (interfaces) Clear boundaries between layers Common Annotations Annotation Purpose @RestController REST controller (combines @Controller + @ResponseBody) @Service Business logic component @Repository Data access component @Transactional Transaction management @Valid Trigger validation @ConfigurationProperties Bind properties to class @EnableMethodSecurity Enable method security Reactive WebFlux Endpoint @RestController @RequestMapping("/api/v1/orders") public class OrderController { private final OrderService orderService; public OrderController (OrderService orderService) { this .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); } } Spring Security JWT @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 Base Spring Boot 3.x, Java 21, Spring WebFlux, Project Reactor, Spring Data JPA, Spring Security 6, OAuth2/JWT, Hibernate, R2DBC, Spring Cloud, Resilience4j, Micrometer, JUnit 5, TestContainers, Mockito, Maven/Gradle