Spring Boot is a framework for building production-ready applications with the Spring ecosystem. It simplifies the development process by providing default configurations and built-in features that streamline setting up and deploying Spring applications. Spring Boot is not just a library; it is a comprehensive framework that includes libraries, tools, and conventions to make Spring application development easier.
Key Features of Spring Boot
- Auto-Configuration: Automatically configures your application based on the dependencies present in the classpath.
- Standalone: Can run applications as standalone Java applications without needing an external server.
- Production Ready: Includes features like health checks and metrics to monitor your application.
- Embedded Servers: Supports embedded servers like Tomcat, Jetty, and Undertow, which simplifies deployment.
Basic Annotations in Spring Boot
@SpringBootApplication- Purpose: A convenience annotation that combines
@Configuration,@EnableAutoConfiguration, and@ComponentScan. - Usage: Marks the main class of a Spring Boot application and enables auto-configuration.
- Example:
java
@SpringBootApplication
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
}
5. @RestController
6. Purpose: A specialized version of @Controller that combines @Controller and @ResponseBody, making it easier to build RESTful web services.
7. Usage: Indicates that a class is a REST controller and its methods return JSON or XML responses directly.
8. Example:
java
@RestController
public class MyController {
@GetMapping("/hello")
public String hello() {
return "Hello, World!";
}
}
9. @RequestMapping
10. Purpose: Maps HTTP requests to handler methods in controllers.
11. Usage: Can be used at the class or method level to specify URL patterns and HTTP methods.
12. Example:
java
@RequestMapping("/api")
public class ApiController {
@GetMapping("/data")
public String getData() {
return "Data";
}
}
13. @Autowired
14. Purpose: Injects dependencies into Spring-managed beans automatically.
15. Usage: Can be used to inject other beans or configuration properties.
16. Example:
java
@Service
public class MyService {
@Autowired
private MyRepository myRepository;
}
17. @Component
18. Purpose: Marks a class as a Spring-managed component.
19. Usage: Used to declare a bean that will be automatically detected through classpath scanning.
20. Example:
java
@Component
public class MyComponent {
// Bean logic
}
21. @Configuration
22. Purpose: Indicates that the class contains bean definitions for the application context.
23. Usage: Used to define additional beans and configuration settings.
24. Example:
java
@Configuration
public class AppConfig {
@Bean
public MyBean myBean() {
return new MyBean();
}
}
25. @Bean
26. Purpose: Indicates that a method produces a bean to be managed by the Spring container.
27. Usage: Used within @Configuration classes to define beans.
28. Example:
java
@Configuration
public class AppConfig {
@Bean
public MyBean myBean() {
return new MyBean();
}
}
29. @Value
30. Purpose: Injects values from properties files or environment variables into fields.
31. Usage: Used to access configuration properties.
32. Example:
java
@Component
public class MyComponent {
@Value("${my.property}")
private String myProperty;
}
33. @EnableAutoConfiguration
34. Purpose: Enables Spring Boot's auto-configuration feature.
35. Usage: Automatically configures Spring application context based on the dependencies present.
36. Example: Typically used within @SpringBootApplication, so explicit use is rare.
Summary
Spring Boot is a framework designed to simplify the setup and development of Spring-based applications. It provides a range of annotations to facilitate configuration, dependency injection, and RESTful service creation, making it easier to build and deploy production-ready applications.