Understanding APIs: 10 API Concepts and Examples

Understanding APIs 10 API Concepts and Examples

If you’re a developer or work in technology, you’ve probably heard of “APIs.” Hearing this word may pique your interest. Assume you’re utilizing a service that needs to retrieve information from another server. APIs enable this by acting as a link between the data and the application.

This article will clarify APIs by describing the fundamental principles and techniques that you may use in your API development cycle. Here is something you need to know before starting using APIs 😂👇.

What you will learn from this article?

  • Basic understanding of APIs, their key concepts, and their importance in your development cycle.
  • Types of APIs and their fundamentals.
  • Best practices in API development
  • Tools or platforms where you can experiment with APIs.

Introduction

APIs are a key component of current programming. They provide for seamless interaction between applications and data. Instead of manually enabling connectivity between apps and data, APIs make this interaction more accessible and efficient for developers.

APIs are essential for letting multiple components in your program to smoothly communicate with your data, whether you’re developing a web application, a mobile application, or integrating a service.

What is an API?

An API (Application Programming Interface) is a framework made up of instructions, functions, and protocols that allow various programs to connect. Its major goal is to provide the methods and data structures that developers may use to interface with their software components.

Consider API to be a waiter at a restaurant: you tell the waiter (API) what you want, and they carry it to the kitchen (server) before returning your meal (data). That is exactly how it works!

APIs function as connections that accept requests from applications, get data from a server, and provide processed data to the application.

Types of APIs

APIs are classified into numerous categories based on their intended application and function. Understanding the different types of APIs allows developers to select the best API for their requirements. Here are the most popular types of APIs:

Public or Open APIs:

These are freely available to any developer, allowing them to access a service’s data and functionality.

The Some Random API platform is an excellent example of a public API provider. That service contains several API endpoints that you may freely access.

Internal or Private APIs:

Their major goal is team collaboration. They are often not accessible to outside developers and are used to integrate systems and services within a team or organization. They are restricted to developers who have been authorized access to the API.

APIs are kept private for a variety of reasons. Some are kept private to protect sensitive data, speed up development for corporate purposes, or improve internal processes. If you’re working on a large-scale application, you should safeguard your API by private it.

Partner APIs:

This is an example of a private API, which is not available to the public. However, they are particularly built for usage by other partners. Access is often offered by a contractual arrangement, which allows partners to integrate and access specific functionality or data.

Now that you’ve learned about the different sorts of APIs, you should understand how and where they may be used. Different types of APIs serve different functions and are best suited for individual projects.

REST APIs

REST (Representational State Transfer) or RESTful APIs are specifications for creating and interacting with online applications. They use normal HTTP techniques and protocols to facilitate communication between clients and servers.

REST APIs are popular in online and mobile apps due to their simplicity, scalability, and statelessness. RESTful APIs, unlike traditional APIs, are not protocols; rather, they use them for interaction.

When the client requests data, the server responds by providing it. That is how easy it is!

Principles of REST APIs

Some architectural principles drive RESTful APIs; their distinct design underpins everything, ensuring they stay efficient and simple to use. Here are some of the REST API’s distinctive principles:

  • Statelessness: Every request sent from a client to a server must include all of the information required to interpret and process the request. The server does not retain any session information about the client. This simplifies the server’s design by eliminating the need to handle and retain session information, allowing the application to scale more effectively. It also helps to provide correct information.
  • Client-Server Architecture: In a REST API, the client and server are independent components that communicate via requests and answers. The client oversees the user interface and experience, whereas the server manages data storage.
  • Uniform Interface: REST APIs use a uniform method of gaining access to resources. To access and change resources, HTTP methods like as GET, POST, PUT, and DELETE are used in conjunction with URIs. This makes REST APIs easier to comprehend and use since developers can depend on patterns they are acquainted with.
  • Cacheability: This is one of the most popular RESTful API concepts among developers. REST APIs distinguish between cacheable and non-cacheable server answers. Caching can minimize the amount of client-server interactions while increasing performance.

This improves efficiency by eliminating unnecessary network calls, lowering latency, and boosting overall performance.

RESTful APIs have an excellent structure and are widely utilized in today’s development cycles. Its main aspects are its principles, which define what REST APIs are.

SOAP APIs

The SOAP (Simple Object Access mechanism) API is a mechanism for transferring structured data in online applications. Unlike REST, which employs simple HTTP methods, SOAP uses XML for message formatting and has a more complicated structure.

SOAP APIs are designed specifically for web applications and have built-in instructions to assure message security, making them ideal for applications requiring high security.

Differences between REST and SOAP

There are clear differences between REST and SOAP, as noticed in the definition above. While both are used for the web, they still differ in architecture, standards, etc. Here are some of its differences:

  • Protocol VS Architectural Style:
    • SOAP: A protocol with standards and rules.
    • REST: An architectural style that uses standard HTTP methods and protocols for interaction between web applications and data.
  • Message Format:
    • SOAP: Uses XML for message formatting.
    • REST: Uses JSON but can also use XML, HTML, or plain text for message formatting.
  • Complexity:
    • SOAP: It’s more complex due to its standards and XML messaging.
    • REST: Simpler and more flexible, easier to implement.
  • Transport:
    • SOAP: Can use various protocols (HTTP, SMTP, etc.).
    • REST: Typically uses HTTPS for communication.

Understanding the distinctions between this protocol and architectural style allows developers to select the suitable protocol depending on the requirements of their applications.

JSON and XML

JSON (JavaScript Object Notation) and XML (eXtensible Markup Language) are two common API communication data types. These formats all serve the same fundamental purpose: to convey data structures between a server and a client in a way that both can comprehend.

JSON

JSON is a lightweight data-interchange format derived from JavaScript. It is easy for humans to read and write and for machines to parse and generate.

XML

XML is a markup language that defines the structure for encoding documents in a format readable to humans and machines. XML is mainly known for its ability to handle complex data structures.

Differences between JSON and XML

  • Readability:
    • JSON: Syntax is more readable, ideal for quick interaction, and more accessible for developers.
    • XML: Comes with a more complex syntax. Best tailored for representing complex data structures and documents.
  • Size:
    • JSON: More compact and lightweight. Results in faster data transmission and less bandwidth usage.
    • XML: Larger due to extensive use of markdown tags.
  • Data Types:
    • JSON: Supports data types such as strings, numbers, arrays, and objects.
    • XML: All data is written in text, requiring parsing for specific data types.
  • Parsing and Performance:
    • JSON: Faster to parse, especially in JavaScript environments, due to compatibility.
    • XML: Slower to parse and process, requiring more resources.
  • Schema Support:
    • JSON: JSON schema is available but not as extensive as XML schema.
    • XML: XML schema is very powerful for verifying document structure and data types.

When interacting with APIs, you may communicate using any data format you wish. It is best to understand the variances, as there is no ‘ideal’ data format to employ in API development. You can choose any of them based on your demands.

When to use

There are cases where you can use JSON as your data format, as well as cases where you can use XML. Knowing when and where to use them is very important.

You can use JSON when:

  • You need a lightweight data format.
  • Working with web APIs, especially in JavaScript environments.
  • Simplicity and readability are essential.
  • You are dealing with simpler data structures and need to reduce bandwidth usage.

You can use XML when:

  • You want to handle complex data structures.
  • Validation of the data format and structure is needed.
  • Working with applications that require extensive metadata and descriptive data.
  • Data interchange needs to be highly extensible and self-descriptive.

By understanding the strengths and cases when you can use both JSON and XML, developers can decide which data format to use based on the needs of their applications.

API Endpoints

At this point in the article, you may be asking what API endpoints are because you’ve seen the word “API endpoints” several times.

An API endpoint is a URL that allows a client to access an API and conduct actions such as obtaining, changing, or deleting data. Endpoints indicate the operations and services offered by an API.

The endpoint allows API to communicate with the application on which you are working, allowing for communication and data exchange. They are accessible via HTTP methods like GET, POST, PUT, and DELETE, which specify the type of operation to be done.

Example of an API Endpoint

Consider a web application that uses a REST API to manage student information. The default URL for the API may be https://api.example.com. Let’s now look at the other endpoints and answers.

Retrieve a list of students:

GET https://api.example.com/students

Here is the response you get:

[
  {
    "id": 1,
    "name": "Opem Didi",
    "email": "opem.didi@school.com"
  },
  {
    "id": 2,
    "name": "Rala Enddrick",
    "email": "rala.enddrick@school.com"
  }
]

In this example, we used the GET method to retrieve information from the system. After that, it gives us the data we requested from the endpoint in JSON format.

Another example could be an endpoint for registering students in the system. Let’s create that and see its response.

POST https://api.example.com/students
Content-Type: application/json

{
  "name": "Opem Didi",
  "email": "opem.didi@school.com"
}

Response:

{
  "id": 1,
  "name": "Opem Didi",
  "email": "opem.didi@school.com"
}
  • In this case, you will notice we are working with the https://api.example.com/students endpoint, basically because we want to add a new student to the system; the only way the users could be accessed is by using that endpoint because it should have information related to the student in it.

Now, let’s think of deleting a specific student’s information. Here’s how we could go about that:

Deleting a Student’s information

  DELETE https://api.example.com/students/1

Response

 {
    "message": "Student deleted successfully."
  }

When deleting a student’s information using an API, addressing the individual data by its ID in the API endpoint assures that you are targeting the relevant record.

Developers can connect with web apps and execute numerous activities using APIs if they understand how endpoints function and see some examples.

HTTP methods

HTTP methods define the action performed on resources identified by the API endpoints. We have almost 40 registered HTTP methods, but here are the four most common ones:

  • GET
  • POST
  • PUT
  • DELETE

Now, we will go into what these methods are used for and provide an example for each of the four most commonly used HTTP methods.

GET

The GET method retrieves data from the server without making any changes to the server data.

An example of how it works was showcased earlier in the endpoint for retrieving students’ information.

An example, once again:

Request:

GET https://api.example.com/students

Response:

[
  {
    "id": 1,
    "name": "Opem Disi",
    "email": "opemi.disi@school.com"
  },
  {
    "id": 2,
    "name": "Rala Enddrick",
    "email": "rals.enddrick@school.com"
  }
]

As seen above, the GET method was used to retrieve the data shown in JSON format from the endpoint.

POST

To create a new resource, use the POST method. Unlike GET, which retrieves data, POST sends data to the server. GET is dependent on the data supplied to the server via POST.

An example of how to utilize the POST method was provided before. The student’s registration example provided a detailed illustration of how the POST method may be utilized.

If you missed it, please have a look again.

Request:

POST https://api.example.com/students
Content-Type: application/json

{
  "name": "Opemi Disi",
  "email": "opemi.disi@student.com"
}

We sent a request using the POST method. This was used because we wanted to add a student’s information to the server.

Here’s the response we get by doing that:

{
  "id": 1,
  "name": "Opemi Disi",
  "email": "opemi.disi@student.com"
}

In the response above, the POST method automatically helped to create and register the new student. That is just how the POST method works.

PUT

This method is used to update existing resources with new data or create a new resource if it doesn’t exist. It replaces the current information of the resource with the data provided in the request.

Let’s take an example of updating a student’s information using the PUT method.

Request:

PUT https://api.example.com/students/1
Content-Type: application/json

{
  "name": "Opemi Disi",
  "email": "opemi.disi@student.com"
}

Response:

{
  "id": 1,
  "name": "Opemipo Hay",
  "email": "opemipo.hay@student.com"
}

In this case, we had to locate the information we wanted to update using its ID. We used the PUT method and added the data we wanted to update.

DELETE

This method is used to delete existing resources. When a DELETE request is made, the server deletes the resource the URI identifies.

For this, we will take an example of deleting a student’s information by its ID.

Request:

DELETE https://api.example.com/students/1

Response:

{
  "message": "Student's information deleted successfully"
}

In the request, we used the DELETE method to delete the user’s information using their ID. After, we got a response saying, “Student’s information deleted successfully.”

HTTP Status Codes

HTTP status codes are responses returned by servers to indicate the result of the client’s request. They play a vital role in API communication by displaying the outcome of the client’s request to the server.

Here are some common out of many HTTP status codes:

  • 200
  • 400
  • 500

200 (OK)

When you receive this answer, the request is successful, and the server returns the desired information.

When a GET request to obtain data is successful, you may expect to receive this answer. The network tab in your development console shows that the operation was successful and the server handled the request as expected.

400 (Not Found)

You receive this answer when the server is unable to locate the requested resource or data. This might be because the data was not properly fetched or the resource does not exist.

This error might occur while attempting to make a GET request for a non-existent user. Let’s take a short look at it.

500 (Internal Server Error)

When you get this response, the server encountered an unexpected condition that prevented it from fulfilling the request.

You could get this response when a server-side error occurred while processing the request.

Request:

POST https://api.example.com/students
Content-Type: application/json

{
  "name": "Opemipo",
  "email": "opemipo.disu@example.com"
}

Response:

{
  "status": 500,
  "message": "Internal server error"
}

A 500 Internal Server Error indicates a general server-side error. It shows that something went wrong on the server, not necessarily due to the client’s request.

While there are a few other HTTP status codes, you can read this article to learn more about them. The ones available in this article are the most common status codes.

Authentication and Authorization

API security is crucial, but authentication and authorization are critical components. In API development, authentication refers to the process of confirming a user’s or application’s identity, which is often accomplished via API keys, OAuth tokens, or user credentials.

Authorization, on the other hand, specifies which resources or processes an authenticated entity is permitted to access.

These procedures guarantee that only authorized users or apps may access the API and carry out activities depending on their permissions.

Basic Concepts of API Keys and OAuth

An API key is a unique identifier that is used to authenticate requests for a project or application.

API keys are supplied in API queries to help identify the caller project or application. They are often used to monitor and manage how the API is utilized. API keys should be kept safe and not accessible in code to avoid unwanted access.

However, they are insecure and should be combined with additional security measures, such as environmental variables.

On the other hand, OAuth (Open Authorization) is a token-based authentication mechanism that allows third-party apps to access user data without disclosing user credentials.

It is extensively used by platforms such as Google and GitHub to provide restricted access to user data. It follows a procedure in which the user approves the application and the application obtains an access token that can be used to perform allowed API queries. It offers a more versatile and safe solution than API keys.

Importance for API Security

  • Prevention of Unauthorized Access: Authentication ensures that only users and applications can access the API, preventing unauthorized access to sensitive data.
  • Rate Limiting: Authentication helps track APIs’ usage, enabling the implementation of rate limits to prevent data misuse.
  • Monitoring: Authentication allows for detailed logging and monitoring of API usage, which can be crucial for identifying errors.

Rate Limiting and Throttling

APIs employ rate limitations to maintain stability and safety. This implies that they restrict the number of queries a user or program may make in a certain length of time. This helps keep servers from being overwhelmed.

It also guarantees that all users in an application receive an equitable distribution of API resources.

To handle rate constraints, applications should progressively increase the duration between retries when a limit is reached. Keep track of your API usage to ensure you don’t exceed these restrictions. By storing frequently used data, you may decrease the amount of queries you make.

Using page numbers and filters can help you manage huge data sets faster, decreasing the demand on the API.

Testing APIs

Testing APIs is critical in the API development process since it ensures that your application connects properly with the server and processes data as intended. Dedicated tools enable you to send API calls, examine and analyze results, and report errors early in the development cycle.

Let’s look at some of the top API testing tools and give a step-by-step instruction on how to use them efficiently.

API testing tools

  • Postman: Postman is a tool that simplifies API development. It allows you to construct and send requests, organize APIs into collections, automate tests, and generate detailed reports. Ideal for both manual and automated testing, Postman supports various HTTP methods, making it flexible for testing.
  • cURL: This command-line technique enables data transfer with URLs.cURL is used mainly because of its accessibility and flexibility, especially for developers comfortable with the command line.
  • Swagger: Swagger provides a suite of tools for API documentation and testing. It allows you to visualize and interact with the API’s resources without manually creating requests.

Guide on how to Test an API

  1. Define the Endpoint and Method
    • Determine the API endpoint you wish to test and the HTTP method (GET, POST, PUT, DELETE) to use.
    • Example: To fetch user data, you might use:
      GET https://api.example.com/users
  2. Set Up the Request
    • Postman: Open Postman, create a new request, enter the endpoint URL, and select the HTTP method. Add necessary headers like API keys and parameters.For a GET request to retrieve users, just set the URL to https://api.example.com/users and include any required headers or parameters.
  3. Send the Request
    • Click “Send” in Postman to execute the request and observe the response.
  4. Analyze the Response
    • Status Code: Indicates the success or failure of the request (e.g., 200 OK, 404 Not Found).
    • Headers: Provide metadata about the response.
    • Body: Contains the data returned by the API, typically in JSON or XML format.
    • Example: A successful GET request might return a status code 200 and a JSON body with user data.
  5. Handle Errors
    • If the request fails, analyze the status code and error message to diagnose the issue.
      • Example: A 404 status code indicates that the endpoint is incorrect or the resource does not exist.
    • Adjust the request accordingly and retry.
  6. Automate Testing
    • Postman supports scripting to automate tests. You can write pre-request scripts to set conditions and test scripts to validate responses.
      • Example: To verify a successful response, add the following script in Postman’s “Tests” tab:
pm.test("Status code is 200", function () {
      pm.response.to.have.status(200);
  });

You can speed up the API testing process by using tools like Postman, cURL, and Swagger, ensuring that your application communicates with external services in a reliable and fast manner.

Conclusion

Any new developer must first understand APIs. They are an essential component of contemporary development, allowing for easy communication and data sharing across programs.

This article has discussed the essential ideas of APIs, such as their kinds, the key principles of REST and SOAP APIs, data formats such as JSON and XML, and the significance of API endpoints and HTTP methods.

In addition, we investigated API security issues such as authentication and authorization, as well as the significance of rate restriction and throttling.

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