Spring Boot Annotations

Let’s go through the annotations used in the provided Spring Boot application and explain them along with some additional values that can be passed into them:

1. @SpringBootApplication:

   • Explanation: This annotation is a combination of multiple Spring annotations, including @Configuration, @EnableAutoConfiguration, and @ComponentScan. It is used to mark the main class of a Spring Boot application.
   • Additional values:
     • exclude: Class[] – Specify classes to be excluded from auto-configuration.
     • scanBasePackages: String[] – Specify base packages to scan for Spring components.

2. @RestController:

   • Explanation: This annotation is used to mark a class as a controller in a Spring MVC application. It indicates that the data returned by the methods will be written directly into the HTTP response body as JSON or XML.
   • Additional values: None.

3. @RequestMapping:

   • Explanation: This annotation is used at the class level or method level to map HTTP requests to handler methods of MVC and REST controllers.
   • Additional values:
     • value: String[] – Specify one or more URL patterns to map the request to.
     • method: RequestMethod[] – Specify HTTP request methods (e.g., GET, POST, PUT, DELETE).
     • params: String[] – Specify request parameters required to invoke the method.
     • headers: String[] – Specify HTTP headers required to invoke the method.
     • consumes: String[] – Specify media types that the method can consume.
     • produces: String[] – Specify media types that the method can produce.

4. @GetMapping, @PostMapping, @PutMapping, @DeleteMapping:

   • Explanation: These annotations are shortcuts for @RequestMapping(method = RequestMethod.GET/POST/PUT/DELETE). They are used to map HTTP GET, POST, PUT, and DELETE requests to handler methods.
   • Additional values: Same as @RequestMapping.

5. @RequestBody:

   • Explanation: This annotation is used to indicate that a method parameter should be bound to the body of the HTTP request.
   • Additional values:
     • required: boolean – Specify whether the request body is required or not. Default is true.

6. @PathVariable:

   • Explanation: This annotation is used to bind a method parameter to a URI template variable.
   • Additional values:
     • value: String – Specify the name of the path variable.

7. @Autowired:

   • Explanation: This annotation is used to automatically wire beans by type from the Spring application context.
   • Additional values:
     • required: boolean – Specify whether the injection is required. Default is true.

8. @Document:

   • Explanation: This annotation is used at the class level to indicate that a class is a MongoDB document and to specify the collection where the document will be stored.
   • Additional values:
     • collection: String – Specify the name of the collection in MongoDB.

9. @Id:

   • Explanation: This annotation is used at the field level to mark a field as the primary key of a MongoDB document.
   • Additional values: None.

10. @Service:

    • Explanation: This annotation is used to mark a class as a service in a Spring application. It indicates that the class contains business logic.
    • Additional values: None.

11. @Repository:

    • Explanation: This annotation is used to mark a class as a repository in a Spring application. It indicates that the class will interact with a database or external data source.
    • Additional values: None.

These annotations play a crucial role in Spring Boot applications by providing metadata to the Spring container, which is used for configuration and bean management.