HTTP Methods

HTTP methods define the action a client wants to perform on a resource. In Spring, we map them to controller methods using annotations like @GetMapping, @PostMapping, etc., or with @RequestMapping(method=...).

1. GET

• Purpose: Retrieve a resource without modifying it
• Safe & Idempotent: Yes
• Spring Annotation: @GetMapping or @RequestMapping(method = RequestMethod.GET)

Example:

@GetMapping("/users/{id}")
public UsergetUser(@PathVariable Long id) {
return userService.findById(id);
}

URL: /users/10 → Returns user with ID 10

2. POST

• Purpose: Create a new resource on the server
• Not Idempotent: Multiple requests create multiple resources
• Spring Annotation: @PostMapping

Example:

@PostMapping("/users")
public UsercreateUser(@RequestBody User user) {
return userService.save(user);
}

URL: /users → Creates a new user

3. PUT

• Purpose: Update or completely replace a resource
• Idempotent: Repeating request has the same effect as once
• Spring Annotation: @PutMapping

Example:

@PutMapping("/users/{id}")
public UserupdateUser(@PathVariable Long id,@RequestBody User user) {
return userService.update(id, user);
}

URL: /users/10 → Updates user with ID 10

4. PATCH

• Purpose: Partially update an existing resource
• Idempotent: Yes, if handled carefully
• Spring Annotation: @PatchMapping

Example:

@PatchMapping("/users/{id}/email")
public UserupdateEmail(@PathVariable Long id,@RequestParam String email) {
return userService.updateEmail(id, email);
}

URL: /users/10/[email protected] → Updates only email

5. DELETE

• Purpose: Remove a resource from the server
• Idempotent: Yes
• Spring Annotation: @DeleteMapping

Example:

@DeleteMapping("/users/{id}")
publicvoiddeleteUser(@PathVariable Long id) {
    userService.delete(id);
}

URL: /users/10 → Deletes user with ID 10

6. OPTIONS

• Purpose: Return allowed HTTP methods for a resource
• Used for: CORS preflight requests or API discovery
• Spring Annotation: @RequestMapping(method = RequestMethod.OPTIONS)

Example:

@RequestMapping(value = "/users", method = RequestMethod.OPTIONS)
public ResponseEntity<?> options() {
return ResponseEntity.ok().allow(HttpMethod.GET, HttpMethod.POST).build();
}

7. HEAD

• Purpose: Retrieve headers of a resource without body
• Safe & Idempotent: Yes
• Spring Annotation: @RequestMapping(method = RequestMethod.HEAD)

Example:

@RequestMapping(value = "/users/{id}", method = RequestMethod.HEAD)
public ResponseEntity<Void>head(@PathVariable Long id) {
return ResponseEntity.ok().build();
}

Quick Reference Table

Key Points

• Idempotent: Same request repeated multiple times has same effect → GET, PUT, DELETE, HEAD, OPTIONS
• Safe: Does not modify server state → GET, HEAD, OPTIONS
• POST vs PUT:
  • POST → create resource, server decides ID/URL
  • PUT → update/replace, client provides ID/URL
• PATCH → partial updates, not idempotent by default

Conclusion

HTTP methods define how clients interact with server resources. In Spring MVC and Spring Boot, they are mapped to controller methods using annotations like @GetMapping, @PostMapping, @PutMapping, @PatchMapping, @DeleteMapping, or the generic @RequestMapping(method=...).