What is HTTP and REST

Understanding HTTP, REST APIs and Parameter Passing with HTTP

HTTP Quick Start

This is a quick and succinct background on HTTP and REST concepts. We provide this here to give readers who are new to the Web Service concept a short introduction to HTTP syntax and REST concepts, as this documentation assumes that you have a basic understanding of the terminology and concept. If you want to understand HTTP, see the recommended tools section for some recommendations.

In the world of web development, the Hypertext Transfer Protocol (HTTP) serves as the foundation for communication between web browsers and servers. HTTP enables the exchange of information, such as web pages, images, and data. In this article, we will explore the basic concepts of HTTP, including requests, responses, and the syntax used to send and receive information between clients and servers.

HTTP Requests

When you type a website URL into your web browser’s address bar and hit enter, your browser sends an HTTP request to the server hosting that website. HTTP requests are made up of several components:

  1. Request Method: The request method specifies the type of action the client wants to perform on the server. The two most common methods are:

    • GET: This method is used to retrieve data from the server. It is typically used when you visit a website or fetch information.
    • POST: This method is used to send data to the server. It is commonly used when you submit a form or upload a file.
  2. URL/URI: The Uniform Resource Locator (URL) or Uniform Resource Identifier (URI) identifies the specific resource the client wants to access. It typically includes the domain name and the path to the resource on the server.

  3. Headers: Headers contain additional information about the request, such as the type of content being sent, accepted content types, authentication credentials, and more. Headers provide crucial context to the server and allow the client and server to understand each other’s capabilities and requirements.

  4. Parameters: Parameters are additional pieces of data that can be included with an HTTP request. They provide specific instructions to the server or help filter and narrow down the requested data. Parameters are often used in GET requests as query parameters, allowing the client to pass data in the URL.

HTTP Responses

When the server receives an HTTP request, it processes the request and sends back an HTTP response. An HTTP response consists of the following components:

  1. Status Code: The status code indicates the outcome of the server’s attempt to fulfill the request. Some common status codes include:

    • 200 OK: The request was successful, and the server is returning the requested data.
    • 404 Not Found: The requested resource could not be found on the server.
    • 500 Internal Server Error: An unexpected error occurred on the server.
  2. Headers: Similar to request headers, response headers provide additional information about the response, such as the content type, cache-control directives, cookies, and more.

  3. Response Body: The response body contains the actual data or content requested by the client. For example, if the client requested a web page, the response body would contain the HTML content of that page.

Syntax and Examples

HTTP requests and responses follow a specific syntax. Here are examples of GET and POST requests:

  • GET Request:
GET /api/products?id=123 HTTP/1.1
Host: api.example.com
Accept: application/json

In the above example, the client is making a GET request to the server’s /api/products endpoint, passing the id parameter with a value of 123. The request also includes the Host header, specifying the server’s domain, and the Accept header, indicating that the client prefers a response in JSON format.

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

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

In this example, the client is making a POST request to the server’s `/api

Understanding REST APIs and Parameter Passing with HTTP

Within the realm of HTTP, a powerful architectural style called REST (Representational State Transfer) has emerged as a standard for designing web APIs. SWS uses REST concepts to provide GET web services. Let’s quickly introduce a few concepts.

What is REST?

REST is an architectural style that provides a set of guidelines for designing networked applications. It emphasizes simplicity, scalability, and interoperability between systems. RESTful APIs (Application Programming Interfaces) enable different software applications to communicate with each other by leveraging the existing HTTP protocol.

In a RESTful architecture, resources (such as data or services) are identified by unique URLs called URIs (Uniform Resource Identifiers). These resources can be accessed and manipulated using standard HTTP methods like GET, POST, PUT, DELETE, etc. By following the principles of REST, developers can create APIs that are easy to understand, consume, and extend.

Understanding Parameters

In the context of REST APIs, parameters play a crucial role in specifying additional information for requests and responses. They allow clients (the applications making the requests) and servers (the applications serving the requests) to exchange data and perform specific actions.

Parameters can be classified into two main types: query parameters and path parameters.

  1. Query Parameters

Query parameters are used to filter, sort, or paginate data. They are appended to the end of a URL after a question mark ‘?’ and separated by ampersands ‘&’. For example:

GET https://api.example.com/products?category=electronics&sort=price&limit=10

In the above example, the query parameters are category=electronics, sort=price, and limit=10. These parameters provide additional instructions to the server, such as retrieving only electronic products, sorting them by price, and limiting the response to 10 items.

  1. Path Parameters

Path parameters are used to identify a specific resource within a URL path. They are denoted by a placeholder surrounded by curly braces ‘{}’. For example:

GET https://api.example.com/products/{id}

In the above example, the {id} placeholder represents a path parameter that would be replaced with an actual value when making a request. For instance, to retrieve the details of a product with an ID of 123, the URL would be:

GET https://api.example.com/products/123

Path parameters are useful when you want to interact with a specific resource or perform operations on it, such as updating or deleting it.


REST APIs have become the de facto standard for building web services due to their simplicity, scalability, and compatibility with the HTTP protocol. Understanding how parameters are passed using HTTP is essential for effectively working with RESTful APIs. By utilizing query parameters and path parameters, clients can provide additional instructions to the server and interact with specific resources. This empowers developers to build flexible and powerful applications that can seamlessly communicate with other services over the web.