Spring

Spring Framework is a comprehensive programming and configuration model for modern Java-based enterprise applications. It offers a robust ecosystem with Spring Boot, Spring Security, Spring Data, and more.

Core Concepts

Dependency Injection

@Service
public class UserService {
    private final UserRepository userRepository;
 
    @Autowired
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
}

Spring Boot

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

REST Controllers

Basic Controller

@RestController
@RequestMapping("/api/users")
public class UserController {
    private final UserService userService;
 
    @GetMapping
    public List<User> getAllUsers() {
        return userService.findAll();
    }
 
    @PostMapping
    public User createUser(@RequestBody User user) {
        return userService.save(user);
    }
}

Data Access

JPA Repository

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    private String name;
    private String email;
 
    // Getters and setters
}
 
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByEmail(String email);
}

Security

Spring Security Configuration

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
 
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
                .antMatchers("/api/public/**").permitAll()
                .anyRequest().authenticated()
            .and()
            .oauth2ResourceServer()
                .jwt();
    }
}

Testing

Unit Testing

@SpringBootTest
class UserServiceTest {
    @MockBean
    private UserRepository userRepository;
 
    @Autowired
    private UserService userService;
 
    @Test
    void whenValidUser_thenUserShouldBeSaved() {
        // Test implementation
    }
}

Best Practices

Project Structure

project/
  ├── src/
  │   ├── main/
  │   │   ├── java/
  │   │   │   └── com/example/
  │   │   │       ├── config/
  │   │   │       ├── controller/
  │   │   │       ├── model/
  │   │   │       ├── repository/
  │   │   │       └── service/
  │   │   └── resources/
  │   └── test/
  └── pom.xml

Configuration Management

Use application.properties/yaml
Profile-based configuration
Externalized configuration
Environment variables

Performance Optimization

Connection pooling
Caching with Spring Cache
Async processing
JPA optimization

Deployment

Production Ready Features

Actuator endpoints
Health checks
Metrics collection
Distributed tracing

Deployment Options

JAR deployment
Docker containers
Kubernetes
Cloud platforms (AWS, GCP, Azure)

Additional Resources

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