POST Method

What is POST Method?

POST is a crucial HTTP method used to send data to a server to create or update a resource. Unlike GET, which is used to retrieve information from the server, POST is used to submit data to be processed to a specified resource. It's generally used when uploading a file or submitting a completed web form.

Principles of POST Method

• Non-idempotent: Unlike GET, POST is non-idempotent, which means that making multiple identical requests can result in different outcomes. Each POST request can create a new resource or change the state of an existing resource.

  For example, if you have a POST /api/orders endpoint to create a new order, sending the same POST request multiple times will create multiple new orders. In code, it would look like this:

POST /api/orders HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "product_id": "12345",
  "quantity": 2
}

• Data Submission: POST is designed for data submission, allowing data to be sent in the request body.

  Example:

POST /api/users HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "name": "John Doe",
  "email": "john.doe@example.com"
}

In this example, a new user is being created with the name John Doe and email john.doe@example.com.

• Resource Creation or Modification: Typically, POST is used to create a new resource, but it can also be used to update an existing resource. This is achieved by including the relevant data in the request body which the server processes to either create a new resource or modify an existing one.

Benefits of Http POST Method

POST is essential when the client needs to send data to the server to create or update resources. It's a secure way of sending data as the data is not appended to the URL (as in GET), but included in the request body.

• Data Encapsulation: Unlike GET, where data is appended to the URL, in POST, data is included in the body of the request, which allows sending large amounts of data. This is especially useful in scenarios like file uploads where the data size can be quite large.

• Security: As data is in the body and not in the URL, POST is a more secure method when sending sensitive data. This is crucial for operations like user login where sensitive data such as passwords are transmitted to the server.

• Versatility: POST can be used for various tasks such as creating a new resource, updating an existing resource, or even submitting form data. This makes POST a versatile HTTP method capable of handling a variety of operations required in modern web applications.

How does POST Method Work?

The operation of the POST method involves the following steps:

1. Client Sends a Request

   The client sends an HTTP request to the server with the POST method, specifying the resource's URI and the data to be processed.

POST /api/orders HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "product_id": "12345",
  "quantity": 2
}

In this step, a new order is being created with a specified product_id and quantity.

2. Server Processes the Request

   The server processes the request, creates or updates the specified resource, and prepares the response. During this phase, the server may interact with a database to store the new data or update existing data based on the information received in the POST request.

3. Server Sends a Response to the Client

   The server sends an HTTP response to the client, indicating the result of the request.

HTTP/1.1 201 Created
Content-Type: application/json

{
  "order_id": "67890",
  "product_id": "12345",
  "quantity": 2,
  "status": "created"
}

Here, the server responds with the details of the newly created order, including a new order_id generated by the server.

Components of a POST Request

A POST request comprises several components:

• URI (Uniform Resource Identifier): The URI identifies where to send the request. For example: /api/orders. It's like the address of the house where you are sending a letter.

• Method: The HTTP method, which in this case is POST. This tells the server what kind of action you want to perform.

• Headers: HTTP headers allow the client to pass additional information about the request and about itself, to the server. For instance, the Content-Type header tells the server the format of the data in the body.

Content-Type: application/json

• Data: The data to be processed, included in the request body.

{
  "product_id": "12345",
  "quantity": 2
}

POST Request Example

POST requests are used to send data to a server. Here are some examples showing how POST requests can be used:

• Creating a New Resource:

POST /api/books HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "title": "The Great Gatsby",
  "author": "F. Scott Fitzgerald"
}

This POST request creates a new book resource on the server. The Content-Type header tells the server that the data is in JSON format.

• Updating an Existing Resource:

  Although traditionally other methods like PUT or PATCH are used to update resources, POST can also be used for updates, especially in cases where the client doesn’t know the URI of the resource.

POST /api/books/1 HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "title": "The Great Gatsby",
  "author": "F. Scott Fitzgerald",
  "year": 1925
}

This POST request updates the book with ID 1 on the server, adding the year of publication.

Conclusion

The POST method is a robust tool in the HTTP protocol suite, enabling the creation and modification of resources on the server. It plays a vital role in the functionality of modern web applications, allowing for interactive features and dynamic content updates.

Learn the difference between GET and POST methods.