What is an API (Application Programming Interface)

In the tech world, APIs (Application Programming Interfaces) are crucial. If you're interested in becoming a web developer or want to understand how websites work, you'll need to familiarize yourself with APIs. Let's break down the concept of an API in simple terms.

What is an API?

An API is a set of rules that allow different software applications to communicate with each other. Think of it like a bridge that connects two systems and lets them share data or services.

To make this clearer, let's use an example:

• Imagine you're at a restaurant. The waiter (API) takes your order (request), brings it to the chef (server), and then brings the food back to you (response).
• Similarly, when you search for a course on a website, you send a request through an API, which then checks the database and sends the result back to you.

Why Do We Need APIs?

APIs help developers to create software programs more easily. Instead of writing complex code from scratch, they can call APIs that already provide the functions they need. For example, if a developer wants to display a weather report, they can use an API to get the data instead of creating the entire system to gather weather data themselves.

APIs are also crucial in building modern websites, where heavy data transfers happen between the client (user) and the server.

How Do APIs Work?

APIs work in a simple step-by-step process:

• Request: A client (user) sends a request through the API's URI (Uniform Resource Identifier).
• Processing: The API forwards the request to the server.
• Response: The server processes the request and sends the response back to the API.
• Delivery: The API returns the server's response to the client.

Think of this as a client-server architecture: the client sends a request, the server processes it, and the API acts as the messenger.curity threats. To provide additional security layers to the data, HTTP headers, query string parameters, or cookies are used.

Types of API Architectures:

1. REST (Representational State Transfer) :A simple, flexible API architecture that uses HTTP methods (GET, POST, PUT, DELETE) for communication.
2. SOAP (Simple Object Access Protocol) :A more rigid protocol that requires XML-based messaging for communication.

Both define a standard communication protocol for the exchange of messages in XML (Extensible Markup Language).

How is an API Different From a Web Application?

An API acts as an interface that allows proper communication between two programs whereas a web application is a network-based resource responsible for completing a single task. Also, it's important to know that "All web services are APIs, but not all APIs are web".

The difference between an API and a web application is that API allows two-way communication and web applications are just a way for users to interact through a web browser. A web application may have an API to complete the requests.

Types of APIs

There are three basic forms of API -

1. WEB APIs

A Web API also called Web Services is an extensively used API over the web and can be easily accessed using the HTTP protocols. A Web application programming interface is an open-source interface and can be used by a large number of clients through their phones, tablets, or PCs.

2. LOCAL APIs

In this type of API, the programmers get the local middleware services. TAPI (Telephony Application Programming Interface), and .NET are common examples of Local APIs.

3. PROGRAM APIs

It makes a remote program appear to be local by making use of RPCs (Remote Procedural Calls). SOAP is a well-known example of this type of API.

Few other types of APIs:

• SOAP (SIMPLE OBJECT ACCESS PROTOCOL): It defines messages in XML format used by web applications to communicate with each other.
• REST (Representational State Transfer): It makes use of HTTP to GET, POST, PUT, or DELETE data. It is basically used to take advantage of the existing data.
• JSON-RPC: It uses JSON for data transfer and is a lightweight remote procedural call defining a few data structure types.
• XML-RPC: It is based on XML and uses HTTP for data transfer. This API is widely used to exchange information between two or more networks.

What are REST APIs?

REST stands for Representational State Transfer, and follows the constraints of REST architecture allowing interaction with RESTful web services. It defines a set of functions (GET, PUT, POST, DELETE) that clients use to access server data. The functions used are:

• GET (retrieve a record)
• PUT (update a record)
• POST (create a record)
• DELETE (delete the record)

Its main feature is that REST API is stateless, i.e., the servers do not save clients' data between requests.

What is a Web API?

Web API Is simply an API for the web. It is an API that can be accessed using the HTTP protocol. It can be built using Java, .nET, etc. It is implemented to extend the functionality of a browser, simplify complex functions, and provide easy syntax to complex code.

The four main types of web APIs are:

• Open API
• Partner API
• Internal API
• Composite API

To Know More: What is Web API and why we use it?

SOAP vs. REST

Also, the major difference is that SOAP cannot make use of REST whereas REST can make use of SOAP. You can also read about the difference between REST API and SOAP API

What is API (Application Programming Interface) Integration?

API (Application Programming Interface) Integration is the connection between two or more applications, via APIs, letting you exchange data. It is a medium through which you can share data and communicate with each other by involving APIs to allow web tools to communicate. Due to the rise in cloud-based products, API integration has become very important.

What is API (Application Programming Interface) Testing?

API (Application Programming Interface) testing is a kind of software testing that analyzes an API in terms of its functionality, security, performance, and reliability. It is very important to test an API so as to check whether it's working as expected or not. If not, again changes are made in the architecture and re-verified.

APIs are the center of software development to exchange data across applications. The API testing includes sending requests to single/multiple API endpoints and validating the response. It focuses majorly on business logic, data responses and security, and performance bottlenecks.

Types of Testing:

• Unit Testing
• Integration Testing
• Security Testing
• Performance Testing
• Functional Testing

Must Read: API Testing in Software Testing

API Testing Tools:

• Postman
• Apigee
• JMeter
• Ping API
• Soap UI
• vREST

How to Create APIs?

Creating an API is an easy task unless you are very well clear on the basic concepts. It's an iterative process (based on feedback) that just includes a few easy steps:

• Plan your goal and the intended users
• Design the API architecture
• Develop (Implement the code) and Test API
• Monitor its working and work on feedback

Must Read: Tips for Building an API

Restrictions of Using APIs

When an API (Application Programming Interface) is made it's not really released as software for download and it has some policies governing its use or restricting its use to everyone, usually, there are three main types of policies governing APIs, are:

• Private: These APIs are only made for a single person or entity (like a company that has spent the resources to make it or bought it).
• Partner: Just like the name it gives the authority to use APIs to some partners of entities that own APIs for their private use.
• Public: You should be aware of them cause you can only find these APIs in the market for your own use if you don't own specific API access from some entity that owns private these APIs for their private use. An example of a Public API is 'Windows API' by Microsoft for more public APIs you can visit this GitHub repository -> https://github.com/public-apis/public-apis .

Advantages of APIs

• Efficiency: API produces efficient, quicker, and more reliable results than the outputs produced by human beings in an organization.
• Flexible delivery of services: API provides fast and flexible delivery of services according to developers' requirements.
• Integration: The best feature of API is that it allows the movement of data between various sites and thus enhances the integrated user experience.
• Automation: As API makes use of robotic computers rather than humans, it produces better and more automated results.
• New functionality : While using API the developers find new tools and functionality for API exchanges.

Disadvantages of APIs

• Cost: Developing and implementing API is costly at times and requires high maintenance and support from developers.
• Security issues: Using API adds another layer of surface which is then prone to attacks, and hence the security risk problem is common in APIs.

Conclusion

By now, you must have had a clear idea of What is API? it's working, types, testing tools used, etc. After understanding these concepts, you can try working on them by implementing some of the concepts in projects. Not just theoretical knowledge, you must also have a practical idea of it by working on it. Developers must have a deep understanding of APIs in order to implement them.