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

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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

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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

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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

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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

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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();
}

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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();
}

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Quick Reference Table

HTTP Method	Purpose	Spring Annotation	Example URL	Idempotent?	Safe?
GET	Retrieve resource	@GetMapping	/users/10	Yes	Yes
POST	Create resource	@PostMapping	/users	No	No
PUT	Update/Replace	@PutMapping	/users/10	Yes	No
PATCH	Partial update	@PatchMapping	/users/10/email	No	No
DELETE	Remove resource	@DeleteMapping	/users/10	Yes	No
OPTIONS	Resource options	@RequestMapping(method=OPTIONS)	/users	Yes	Yes
HEAD	Resource headers	@RequestMapping(method=HEAD)	/users/10	Yes	Yes

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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

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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=...).