Sending Data with POST Requests in Kotlin

Welcome to this lesson on sending data with POST requests. As you continue your exploration of interacting with RESTful APIs, you'll learn how to send data to a server using the POST method. POST requests are essential when you want to create new resources or submit data, such as filling out a web form or adding a new entry to a database. Unlike GET requests, which you have already encountered, POST requests do not solely retrieve information; they actually transmit data to an API.

Understanding these differences is crucial as you expand your skill set in HTTP methods. Let’s dive deeper into utilizing POST requests to comprehend how they stand apart from GET requests.

Before diving into POST requests, let's briefly compare them to GET requests:

• GET Requests:

  • Purpose: Retrieve data from a server.
  • Data Location: Data is sent in the URL as path or query parameters.
  • Success Status: Expect a 200 status code for successful data retrieval.
  • Security and Data Visibility: Data is appended to the URL, making it visible in browser history, server logs, and network tools, which is unsuitable for sensitive information.

• POST Requests:

  • Purpose: Send data to a server to create or update a resource, such as submitting a form, uploading a file, or adding a new item to a database.
  • Data Location: Data is sent in the request body.
  • Success Status: Expect a 201 status code for successful resource creation.
  • Security and Data Visibility: Data is sent in the request body, making it less exposed and more suitable for transmitting sensitive information.

These differences clarify when to use each method. POST requests, in particular, require careful handling of the request body.

For POST requests, the request body is crucial as it holds the data you want to send to the server. This data is usually structured in formats like JSON, XML, or form data, with JSON being a common choice due to its readability and compatibility.

Here's an example of a JSON request body:

{
  "title": "Learn Kotlin OkHttp library",
  "description": "Complete a course on Kotlin API calls.",
  "done": false
}

This represents a new todo item, including a title, completion status, and description. Noticeably, we are not sending an id, as this is typically managed by the server upon resource creation.

With a solid understanding of GET vs. POST and the role of the request body, you’re ready to explore how to utilize Kotlin's OkHttp library to handle POST operations.