@RequestMapping

@RequestMapping is a core Spring annotation that maps HTTP requests to controller methods. It allows specifying URLs, HTTP methods (GET, POST, PUT, DELETE, etc.), request and response content types (like JSON or XML), and headers (useful for API versioning or access control). It forms the foundation of request routing in Spring MVC and Spring Boot.

What is @RequestMapping?

@RequestMapping is used to:

• Map URL paths to controller methods
• Specify HTTP methods (GET, POST, PUT, DELETE)
• Match headers for API versioning or access control
• Define consumes and produces content types (e.g., JSON, XML)

⚠️ Default behavior: If the HTTP method is not specified, @RequestMapping matches all HTTP methods.

Caution: It’s best to specify the HTTP method to avoid unintended matches.

Basic Example

@RequestMapping(value = "/users", method = RequestMethod.GET)
public List<User>getUsers() {
return userService.findAll();
}

• value → URL path
• method → HTTP method (GET, POST, etc.)

Class-Level vs Method-Level Mapping

Class-Level Mapping

Defines a base URL for all methods in a controller.

@RestController
@RequestMapping("/api/users")
publicclassUserController { }

Method-Level Mapping

Defines specific endpoints under the base URL.

@GetMapping
public List<User>getAllUsers() {
return userService.findAll();
}

Final URL: /api/users

HTTP Method-Specific Annotations

Spring provides shortcuts over @RequestMapping(method=...) for clarity:

• @GetMapping → GET → Fetch resource(s)
• @PostMapping → POST → Create resource
• @PutMapping → PUT → Update full resource
• @PatchMapping → PATCH → Partial update
• @DeleteMapping → DELETE → Remove resource

Prefer these shortcuts for cleaner and more readable code.

Advanced @RequestMapping Attributes

Examples

// Consume JSON and produce JSON
@PostMapping(consumes = "application/json", produces = "application/json")
public UsersaveUser(@RequestBody User user) {
return user;
}

// Handle multiple HTTP methods
@RequestMapping(value = "/status", method = {RequestMethod.GET, RequestMethod.POST})
public Stringstatus() {
return"OK";
}

// Path variable with regex
@GetMapping("/users/{id:[0-9]+}")
public UsergetUser(@PathVariable Long id) {
return userService.findById(id);
}

// Multiple paths
@RequestMapping(value = {"/users", "/members"}, method = RequestMethod.GET)
public List<User>getAll() {
return userService.findAll();
}

Best Practices

• Use HTTP method-specific annotations (@GetMapping, @PostMapping) for readability
• Use class-level @RequestMapping for base URLs
• Keep controllers thin, delegate business logic to service layer
• Version APIs using headers, paths, or media types
  • URL versioning: /api/v1/users
  • Header versioning: X-API-VERSION=1
  • Media type versioning: Accept=application/vnd.company.v1+json
• Always use DTOs instead of exposing entities directly
• Use ResponseEntity for production-ready responses
• Validate request bodies with @Valid

Conclusion

@RequestMapping is the foundation of request routing in Spring MVC and Spring Boot.

• Maps URLs, HTTP methods, headers, and content types to controller methods
• Combined with controllers, it provides robust, production-ready request handling
• For cleaner code, prefer HTTP method-specific annotations (@GetMapping, @PostMapping, etc.)