HTTP Methods - GET, POST

Types of HTTP Methods #

Main Methods

• GET : Retrieve a resource
• POST : Process request data, primarily used for creation
• PUT : Replace a resource; if the resource doesn't exist, create it
• PATCH : Partially modify a resource
• DELETE : Delete a resource

Other Methods

• HEAD : Same as GET, but excludes the message body, returning only the status line and headers
• OPTIONS : Describes the communication options (methods) available for the target resource (primarily used in CORS)
• CONNECT : Establishes a tunnel to the server identified by the target resource
• TRACE : Performs a message loop-back test along the path to the target resource

GET #

• Retrieve a resource
• Data to be sent to the server is passed via the query string
• Although it's possible to send data using the message body, it's not recommended as many places do not support it

POST #

• Process request data
• Send request data to the server via the message body
• The server processes the request data
• Performs all functions that process data received through the message body.
• Primarily used for creating new resources or processing tasks with the transmitted data

POST /members HTTP/1.1
Content-Type: application/json

{
  "username" : "hello",
  "age" : 20
}

What does "process request data" mean? Examples

• Specification: The POST method requests that the target resource process the representation enclosed in the request according to the resource's own specific semantics. (Google Translate)
• For example, creating a new resource not identified by P.

1. Create a new resource (registration)

   • Create a new resource that the server has not yet identified.

2. Process request data

• Cases where a process needs to be handled, beyond simply creating or modifying data.
• E.g., in an order, from "payment complete" to "delivery started" to "delivery complete," where the state of a process changes beyond a simple value modification.
• A new resource may not necessarily be created as a result of a POST request.
• E.g., POST /orders/{orderId}/start-delivery (control URI)

3. Cases that are ambiguous to handle with other methods
   • E.g., when you need to pass query data as JSON, but it's difficult to use the GET method.
   • If ambiguous, POST is used for the following functions:

• Providing a block of data, such as the fields entered into an HTML form, to a data-handling process (e.g., user registration, orders using information entered in an HTML FORM).

• Posting messages to a bulletin board, newsgroup, mailing list, blog, or similar group of articles (e.g., writing a forum post, adding a comment).

• Creating a new resource that the server has not yet identified (e.g., creating a new order).

• Appending data to an existing resource (e.g., adding content to the end of a document).

• Summary: When a POST request comes to this resource URI, how the request data should be processed must be defined separately for each resource -> nothing is predefined.