Mastering HTTP Methods in Spring Boot: Quick Reference Guide

HTTP Methods: Definitions & Descriptions

HTTP Method	Definition / Description
GET	Retrieve data from a server at the specified resource. It is read-only and should have no side effects (i.e., not modify data). Commonly used for fetching lists, details, or static content.
POST	Submit data to the server to create a new resource. The server processes the request and returns the new resource or a success status. Used in forms, sign-ups, data submissions.
PUT	Replace an existing resource entirely with the provided data. If the resource does not exist, some APIs may create it (though this is debated). Used for complete updates.
PATCH	Partially update an existing resource. Only the fields sent in the request are modified; others remain unchanged. More efficient than PUT for small changes.
DELETE	Remove a resource from the server. It targets a specific resource or dataset. Often used for deleting users, posts, files, etc.
HEAD	Same as GET, but only returns headers, not the response body. Useful for checking if a resource exists or retrieving metadata.
OPTIONS	Returns allowed HTTP methods and CORS policies for a resource. Often used in preflight requests in cross-origin setups.
TRACE	Echoes back the received request. Mostly used for debugging and testing, but generally disabled for security reasons.
CONNECT	Establishes a tunnel, typically for HTTPS connections through proxies. Rarely used in app-level programming.

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Mastering HTTP Methods in Spring Boot

HTTP Method	Spring Boot Annotation	Usage Description	Typical Responses
GET	@GetMapping	Retrieve resource(s) without modifying anything.	200 OK, 204 No Content, 404 Not Found
POST	@PostMapping	Create a new resource.	201 Created, 400 Bad Request, 409 Conflict, 422 Unprocessable Entity, 500 Internal Server Error
PUT	@PutMapping	Replace an existing resource entirely.	200 OK, 204 No Content, 400 Bad Request, 404 Not Found
PATCH	@PatchMapping	Update a part of the existing resource.	200 OK, 204 No Content, 400 Bad Request, 404 Not Found
DELETE	@DeleteMapping	Delete a resource.	200 OK, 204 No Content, 404 Not Found, 400 Bad Request

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Typical HTTP Response Codes

Code	Meaning	When to Use
200	OK	Request succeeded (GET, PUT, PATCH, DELETE).
201	Created	Resource created successfully (POST).
204	No Content	Success with no body returned.
400	Bad Request	Invalid input or request syntax.
401	Unauthorized	Authentication is required or failed.
403	Forbidden	Authenticated but not authorized.
404	Not Found	Resource doesn’t exist.
409	Conflict	Resource already exists or version conflict.
422	Unprocessable Entity	Validation passed structurally but failed semantically.
500	Internal Server Error	Unexpected error on server side.