---
id: irahardianto/awesome-agv/spring-boot-idioms
version: "11ec04ec"
license: MIT
install: manual
updated: 2026-07-17
---

# Spring Boot Idioms — Learn idiomatic Spring Boot 3.x patterns grounded in auto-configuration, constructor injection, and actuator-driven observability. Covers dependency injection best practices, Spring Data JPA query methods and projections, REST controller design with DTOs, and structured logging for production readiness. Includes testing patterns for integration and controller slices.

Publisher: irahardianto · Stars: 150 · Updated: 2026-07-17

Install (manual): `git clone https://github.com/irahardianto/awesome-agv`

## SKILL.md

## Spring Boot Idioms and Patterns

Spring Boot (3.x) rewards auto-configuration, constructor injection, and actuator-driven observability. Idiomatic Spring = annotation-driven, testable, production-ready.

> Scope: Spring Boot-specific patterns. For Java: `@.agents/skills/java-idioms/SKILL.md`.

### Dependency Injection

1. **Constructor injection only** — never field injection:
   ```java
   @Service
   public class TaskService {
       private final TaskRepository repository;
       private final TaskMapper mapper;

       public TaskService(TaskRepository repository, TaskMapper mapper) {
           this.repository = repository;
           this.mapper = mapper;
       }
   }
   ```

2. **`@ConfigurationProperties`** over `@Value` for typed config.

### Spring Data JPA

1. **Query methods for simple queries:**
   ```java
   interface TaskRepository extends JpaRepository<Task, UUID> {
       List<Task> findByStatusOrderByCreatedAtDesc(TaskStatus status);
       @Query("SELECT t FROM Task t WHERE t.priority = :priority AND t.status = 'ACTIVE'")
       List<Task> findActivByPriority(@Param("priority") Priority priority);
   }
   ```

2. **Projections** for read-only views — avoid loading full entities.
3. **`@Transactional`** on service methods, never on repositories.

### REST Controllers

1. **`@RestController` + DTOs** — never expose entities directly:
   ```java
   @RestController
   @RequestMapping("/api/v1/tasks")
   public class TaskController {
       @PostMapping
       @ResponseStatus(HttpStatus.CREATED)
       public TaskResponse create(@Valid @RequestBody CreateTaskRequest request) {
           return taskService.create(request);
       }
   }
   ```

2. **`@ControllerAdvice`** for global exception handling.

### Actuator and Observability

1. **Actuator endpoints** enabled for health, metrics, info.
2. **Micrometer** for custom metrics.
3. **Structured logging** with MDC for correlation IDs.

### Testing

> For universal testing principles, see `.agents/rules/testing-strategy.md`. Below: language-specific patterns only.

1. **`@SpringBootTest`** for integration, `@WebMvcTest` for controller slices:
   ```java
   @WebMvcTest(TaskController.class)
   class TaskControllerTest {
       @Autowired MockMvc mockMvc;
       @MockBean TaskService taskService;

       @Test
       void createTask_returns201() throws Exception {
           mockMvc.perform(post("/api/v1/tasks")
               .contentType(MediaType.APPLICATION_JSON)
               .content("{\"title\":\"Test\",\"priority\":\"HIGH\"}"))
               .andExpect(status().isCreated());
       }
   }
   ```

2. **TestContainers** for database integration tests.

### Related
- Java Idioms @.agents/skills/java-idioms/SKILL.md
- Database Design Principles @.agents/rules/database-design-principles.md
- API Design Principles @.agents/rules/api-design-principles.md


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