springboot
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starter

1. Understand Framework Basics

  • A framework is a higher abstraction layer over a core library to solve common problems.
  • Spring Boot simplifies working with Spring Framework by reducing configuration.

2. Dependency Injection (DI) Basics

  • Define dependencies using constructor injection or annotations like @Autowired.
  • Beans and components are created and managed by the Spring container (IoC).

3. Set Up a Spring Boot Project

  • Use the Spring Initializr:
    1. Go to start.spring.io.
    2. Choose:
      • Project (Maven/Gradle).
      • Language (Java, Kotlin, Groovy).
      • Spring Boot Version.
      • Metadata (Group ID, Artifact ID, etc.).
    3. Add dependencies (e.g., Spring Web, Spring Data JPA, H2, etc.).
    4. Generate and download the project.

4. Build and Run the Application

Using IDE (e.g., VS Code, IntelliJ)

  • Open the main class and click Run or Debug.

Using Terminal

  • To run with Maven Wrapper:

    ./mvnw spring-boot:run

  • To package and run the JAR:

    ./mvnw package
java -jar target/your-app-name.jar

5. Declare Beans and Components

  • Create beans using @Bean or by annotating classes with:
    • @Component (generic).
    • @Service (business logic).
    • @Repository (data access).
    • @RestController (web API).

6. Configure Properties

  • Use application.properties or application.yml to override defaults:

    spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.username=sa
spring.datasource.password=password
server.port=8081

  • Use environment variables to configure (e.g., SPRING_DATASOURCE_URL).

7. Develop Application Layers

Persistence Layer

  • Create JPA entities and repositories:

    @Entity
public class Book { ... }

public interface BookRepository extends JpaRepository<Book, Long> { ... }

Service Layer

  • Create services and inject dependencies:

    @Service
public class BookService { ... }

Controller Layer

  • Define REST endpoints using annotations like @GetMapping and @PostMapping:

    @RestController
public class BookController {
    private final BookService bookService;

    @Autowired
    public BookController(BookService bookService) { ... }
}

8. Logging

  • Default logging uses Logback.

  • Customize logging levels in application.properties:

    logging.level.org.springframework=DEBUG
logging.level.com.example=TRACE

  • Advanced configurations can be added to logback.xml.

9. Testing

Unit Testing

  • Mock dependencies with @Mock and @InjectMocks using Mockito.

Integration Testing

  • Use @SpringBootTest to test the entire application:

    @SpringBootTest
public class BookControllerTest { ... }

10. Next Steps

  • Explore more features of Spring Boot (e.g., Security, Microservices).
  • Follow additional tutorials for specific use cases like building REST APIs or integrating databases.

This breakdown provides a structured way to approach Spring Boot development. Let me know if you'd like detailed code examples or further clarification!

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