Spring Boot Standard CRUD

Overview

Deliver 100% functional, production-ready CRUD services using standard Spring Boot annotations. This skill omits the complexity of DDD-adapters in favor of a direct, layered architecture (Controller -> Service -> Repository -> Model) with centralized validation and robust error handling.

When to Use

• Quickly scaffold a functional REST API for a new or existing entity.
• Implement standard CRUD operations (List, Find, Create, Update, Delete) with input validation.
• Ensure consistent error responses across the API using a Global Exception Handler.
• Trigger phrases: "implement standard CRUD for [Entity]", "crear un CRUD funcional para [Entidad]", "implementar servicios Spring Boot con anotaciones", "necesito un CRUD completo con validaciones y manejo de errores".

Instructions

Follow these steps to implement a complete and functional CRUD:

0. Dependency Verification

Before implementing, verify that the pom.xml contains:

• spring-boot-starter-web
• spring-boot-starter-data-jpa
• h2 (runtime scope)
• lombok (optional: true)
• spring-boot-starter-validation
• spring-boot-devtools (optional/runtime scope) If any are missing, notify the user or suggest adding them.

1. Model (Entity) Configuration

Create the entity in the .model package.

• Use @Entity and @Table.
• Use Lombok @Data, @NoArgsConstructor, and @AllArgsConstructor.
• Apply jakarta.validation.constraints (e.g., @NotBlank, @Positive, @Email) directly on fields.
• Set @Column(nullable = false) where appropriate.

2. Repository Interface

Create the repository in the .repository package.

• Extend JpaRepository<Entity, Long>.
• Keep it a simple interface.

3. Service Layer (Interface & Implementation)

Create the interface in .service and implementation in .service.impl (or same package).

• Use @Service and @RequiredArgsConstructor.
• Update Logic: Explicitly map fields from the request to the existing database entity to avoid overwriting IDs or missing fields.
• Error Handling: Use orElseThrow() with custom exceptions or RuntimeException for "Not Found" cases.

4. REST Controller

Create the controller in the .controller package.

• Use @RestController, @RequestMapping, and @RequiredArgsConstructor.
• Use @Valid on @RequestBody for POST and PUT operations.
• Return appropriate status codes: 201 for Creation, 204 for Deletion (optional), 200 for others.

5. Robustness: Global Exception Handler

CRITICAL: Always ensure a @RestControllerAdvice exists to catch MethodArgumentNotValidException and return a clean JSON with validation errors. If it doesn't exist, create it.

6. Database Configuration (H2)

100% Functional: If no external database is configured, automatically add the H2 configuration to src/main/resources/application.properties (or .yml) so the project can run immediately.

• Enable H2 Console: spring.h2.console.enabled=true
• Set Datasource URL: spring.datasource.url=jdbc:h2:mem:testdb
• Set Driver and Auth (Optional but recommended):
  • spring.datasource.driver-class-name=org.h2.Driver
  • spring.datasource.username=sa
  • spring.datasource.password=
• Set DDL Auto: spring.jpa.hibernate.ddl-auto=update
• SQL Debugging: Add spring.jpa.show-sql=true and spring.jpa.properties.hibernate.format_sql=true for easier terminal reading.

7. Verification (Testing)

• Generate a Smoke Test or a simple @DataJpaTest to verify persistence logic.

Best Practices

• Never expose internal IDs in URLs if they are sensitive, but for standard CRUD, Long IDs are acceptable.
• Stay Immutable: Use Lombok to reduce boilerplate but keep service dependencies final.
• Validation: Every String field should usually have @NotBlank. Every numeric field should have @Positive or @Min.

Example

Refer to references/example-crud.md for a full implementation of a "Producto" entity.