Must know for Java Spring professionals ( AI Generated )
## Spring Framework Tutorial
This comprehensive tutorial covers essential topics in the Spring Framework, focusing on core concepts, Spring Boot, and advanced features.
## 1. Dependency Injection (DI) and Inversion of Control (IoC)
Dependency Injection (DI) and Inversion of Control (IoC) are fundamental principles in Spring that promote loose coupling and easier testing[2][5].
- **IoC**: The Spring container manages object creation and lifecycle, inverting control from the application to the framework[2].
- **DI**: Dependencies are injected into objects rather than created by the objects themselves[5].
Example of constructor injection:
```java
public class UserService {
private final UserRepository userRepository;
@Autowired
public UserService(UserRepository userRepository) {
this.userRepository = userRepository;
}
}
```
## 2. Bean Lifecycle and Scopes
Beans in Spring have a lifecycle and different scopes that determine their creation and destruction[1].
- **Lifecycle**: Initialization and destruction callbacks (e.g., @PostConstruct, @PreDestroy)
- **Scopes**: Singleton (default), Prototype, Request, Session, Application
## 3. ApplicationContext and BeanFactory
- **ApplicationContext**: Advanced container that extends BeanFactory, providing additional enterprise-specific functionality[1].
- **BeanFactory**: Basic container for DI, lazily instantiates beans[2].
## 4. XML vs. Java-based Configuration
Spring supports both XML and Java-based configuration[1].
XML configuration:
```xml
<bean id="userService" class="com.example.UserService">
<constructor-arg ref="userRepository" />
</bean>
```
Java-based configuration:
```java
@Configuration
public class AppConfig {
@Bean
public UserService userService(UserRepository userRepository) {
return new UserService(userRepository);
}
}
```
## 5. Annotations: @Component, @Autowired, @Qualifier, @Value
- **@Component**: Marks a class as a Spring-managed component[1].
- **@Autowired**: Injects dependencies automatically[5].
- **@Qualifier**: Specifies which bean to inject when multiple candidates exist.
- **@Value**: Injects values from properties files or environment variables.
## 6. Pointcuts, Advice, Joinpoints, Aspects
These are key concepts in Aspect-Oriented Programming (AOP)[1]:
- **Pointcut**: Defines where advice should be applied.
- **Advice**: The action taken at a particular joinpoint.
- **Joinpoint**: A point in the execution of a program.
- **Aspect**: A modularization of concerns that cut across multiple classes.
## 7. Common AOP Annotations: @Aspect, @Before, @After
```java
@Aspect
@Component
public class LoggingAspect {
@Before("execution(* com.example.service.*.*(..))")
public void logBefore(JoinPoint joinPoint) {
// Logging logic
}
}
```
## 8. JDBC Template
Spring's JdbcTemplate simplifies JDBC operations, handling resource management and exception translation[1].
```java
@Autowired
private JdbcTemplate jdbcTemplate;
public User findById(long id) {
return jdbcTemplate.queryForObject(
"SELECT * FROM users WHERE id = ?",
new Object[]{id},
(rs, rowNum) -> new User(rs.getLong("id"), rs.getString("name"))
);
}
```
## 9. Spring ORM with Hibernate
Spring provides integration with Hibernate for Object-Relational Mapping[1].
```java
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
// Getters and setters
}
```
## 10. Transactions: Programmatic vs Declarative
Spring supports both programmatic and declarative transaction management[1].
Declarative (preferred):
```java
@Transactional
public void transferMoney(Account from, Account to, BigDecimal amount) {
// Transfer logic
}
```
## 11. Spring Boot Starters and Dependencies
Spring Boot starters are dependency descriptors that simplify project setup[3].
```xml
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
```
## 12. Auto-configuration
Spring Boot's auto-configuration automatically configures your application based on the dependencies present[3][6].
## 13. Embedded Servers (Tomcat, Jetty)
Spring Boot includes embedded servers, eliminating the need for external application servers[3].
## 14. Spring Boot Actuator
Actuator provides production-ready features for monitoring and managing your application[3].
## 15. DispatcherServlet Flow
The DispatcherServlet is the front controller in Spring MVC, handling all incoming requests[1].
## 16. RESTful Web Services
Spring simplifies creating RESTful web services[1].
```java
@RestController
@RequestMapping("/api/users")
public class UserController {
@GetMapping("/{id}")
public User getUser(@PathVariable Long id) {
// Fetch and return user
}
}
```
## 17. RequestMapping: @GetMapping, @PostMapping, etc.
These annotations simplify request mapping for different HTTP methods[1].
## 18. Exception Handling with @ControllerAdvice
```java
@ControllerAdvice
public class GlobalExceptionHandler {
@ExceptionHandler(UserNotFoundException.class)
public ResponseEntity<String> handleUserNotFound(UserNotFoundException ex) {
return ResponseEntity.status(HttpStatus.NOT_FOUND).body(ex.getMessage());
}
}
```
## 19. Authentication and Authorization
Spring Security provides comprehensive security services for Java EE-based applications[1].
## 20. Security Filters and Interceptors
These components in Spring Security handle various aspects of application security[1].
## 21. JWT (JSON Web Tokens) Integration
Spring Security can be configured to work with JWT for stateless authentication[1].
## 22. OAuth2/OpenID Connect
Spring Security OAuth provides support for OAuth2 and OpenID Connect[1].
## 23. Spring Data JPA and Repositories
Spring Data JPA simplifies data access layer implementation[1].
```java
public interface UserRepository extends JpaRepository<User, Long> {
List<User> findByLastName(String lastName);
}
```
## 24. Query Methods and Custom Queries
Spring Data allows defining query methods by method names and custom queries using @Query[1].
## 25. Paging and Sorting
```java
Page<User> findAll(Pageable pageable);
```
## 26. Microservices Architecture
Spring Cloud provides tools for building microservices-based applications[1].
## 27. Service Discovery (Eureka)
Eureka server from Spring Cloud Netflix enables service discovery[1].
## 28. API Gateway (Spring Cloud Gateway)
Spring Cloud Gateway provides a powerful and flexible API Gateway[1].
## 29. Circuit Breakers (Resilience4j, Hystrix)
These libraries provide circuit breaker functionality for fault tolerance[1].
## 30. Config Server and Distributed Configurations
Spring Cloud Config provides server and client-side support for externalized configuration[1].
## 31. Batch Processing Essentials
Spring Batch provides reusable functions for processing large volumes of records[1].
## 32. Chunk-oriented Processing
Spring Batch uses a chunk-oriented processing style[1].
## 33. Job Parameters and Scheduling
Spring Batch allows parameterized job execution and integration with schedulers[1].
## 34. Reactive Programming Concepts
Spring WebFlux supports reactive programming for building non-blocking, event-driven applications[1].
## 35. Mono and Flux
These are the core types in Project Reactor, used in Spring's reactive stack[1].
## 36. Reactive REST APIs
```java
@GetMapping("/users")
public Flux<User> getAllUsers() {
return userRepository.findAll();
}
```
## 37. Unit and Integration Testing with @SpringBootTest
```java
@SpringBootTest
class UserServiceTest {
@Autowired
private UserService userService;
@Test
void testGetUser() {
// Test logic
}
}
```
## 38. Mocking with Mockito
```java
@MockBean
private UserRepository userRepository;
@Test
void testGetUser() {
when(userRepository.findById(1L)).thenReturn(Optional.of(new User(1L, "John")));
// Test logic
}
```
## 39. TestRestTemplate and MockMvc
These utilities facilitate testing of REST controllers[1].
## 40. Event Handling and Application Events
Spring's event mechanism allows beans to communicate with each other[1].
```java
@EventListener
public void handleUserCreatedEvent(UserCreatedEvent event) {
// Handle event
}
```
This tutorial covers the core concepts and advanced features of the Spring Framework, providing a solid foundation for building robust Java applications.
Citations:
[1] https://www.geeksforgeeks.org/spring/
[2] https://www.digitalocean.com/community/tutorials/spring-ioc-bean-example-tutorial
[3] https://docs.spring.io/spring-boot/reference/features/developing-auto-configuration.html
[4] https://www.danvega.dev/blog/spring-boot-crash-course
[5] https://www.youtube.com/watch?v=FHii0xjGN5g
[6] https://docs.spring.io/spring-boot/docs/2.1.2.RELEASE/reference/html/boot-features-developing-auto-configuration.html
[7] https://www.javatpoint.com/spring-tutorial
[8] https://stackoverflow.com/questions/9403155/what-is-dependency-injection-and-inversion-of-control-in-spring-framework
[9] https://docs.spring.io/spring-boot/docs/1.5.11.RELEASE/reference/html/boot-features-developing-auto-configuration.html
[10] https://www.marcobehler.com/guides/spring-framework
[11] https://www.geeksforgeeks.org/spring-difference-between-inversion-of-control-and-dependency-injection/
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