Key Annotations for Spring Boot Microservices

@RestController

Combines @Controller and @ResponseBody. It indicates that a class is a Spring MVC controller where every method returns a domain object instead of a view.

        @RestController
        @RequestMapping("/api")
        public class MyController {
            @GetMapping("/hello")
            public String sayHello() {
                return "Hello, World!";
            }
        }
    

@RequestMapping

Used to map web requests to a specific handler class or method. It can be applied at the class or method level.

        @RestController
        @RequestMapping("/api")
        public class MyController {
            @RequestMapping(value = "/hello", method = RequestMethod.GET)
            public String sayHello() {
                return "Hello, World!";
            }
        }
    

@GetMapping

A shortcut for @RequestMapping with method=RequestMethod.GET. Used for handling GET requests.

        @RestController
        public class MyController {
            @GetMapping("/hello")
            public String sayHello() {
                return "Hello, World!";
            }
        }
    

@PostMapping

A shortcut for @RequestMapping with method=RequestMethod.POST. Used for handling POST requests.

        @RestController
        public class MyController {
            @PostMapping("/create")
            public String create(@RequestBody String data) {
                return "Data created: " + data;
            }
        }
    

@PutMapping

A shortcut for @RequestMapping with method=RequestMethod.PUT. Used for handling PUT requests.

        @RestController
        public class MyController {
            @PutMapping("/update")
            public String update(@RequestBody String data) {
                return "Data updated: " + data;
            }
        }
    

@DeleteMapping

A shortcut for @RequestMapping with method=RequestMethod.DELETE. Used for handling DELETE requests.

        @RestController
        public class MyController {
            @DeleteMapping("/delete/{id}")
            public String delete(@PathVariable("id") String id) {
                return "Deleted ID: " + id;
            }
        }
    

@PathVariable

Used to extract values from the URI and bind them to method parameters.

        @RestController
        public class MyController {
            @GetMapping("/user/{id}")
            public String getUserById(@PathVariable("id") String id) {
                return "User ID: " + id;
            }
        }
    

@RequestBody

Maps the body of the HTTP request to a Java object. Useful for handling JSON data.

        @RestController
        public class MyController {
            @PostMapping("/create")
            public String createUser(@RequestBody User user) {
                return "User created: " + user.getName();
            }
        }

        class User {
            private String name;
            public String getName() { return name; }
            public void setName(String name) { this.name = name; }
        }
    

@RequestParam

Used to extract query parameters from the URL.

        @RestController
        public class MyController {
            @GetMapping("/greet")
            public String greet(@RequestParam("name") String name) {
                return "Hello, " + name;
            }
        }
    

@ExceptionHandler

Used to handle exceptions in a specific controller or globally.

        @RestController
        @ControllerAdvice
        public class ExceptionController {
            @ExceptionHandler(Exception.class)
            public String handleException(Exception e) {
                return "Error: " + e.getMessage();
            }
        }
    

@CrossOrigin

Enables cross-origin resource sharing (CORS).

        @RestController
        @CrossOrigin(origins = "http://example.com")
        public class MyController {
            @GetMapping("/data")
            public String getData() {
                return "Data";
            }
        }