July 25, 2024 API Development

What Are API Methods?

Whether you’re fetching weather updates for your smart home or processing a payment for an online purchase, being able to fetch and write data is critical. At the heart of this data exchange lies the unsung hero: the Application Programming Interface (API). For developers, knowledge of RESTful API development is crucial, especially when working with modern applications that are highly dependent on APIs.

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In this guide, we’ll explore the world of API methods, exploring the different types, the underlying protocols they use, and the best practices for API development and security. By the end, you’ll have a solid grasp of how API methods work, allowing you to build and interact with APIs fluently. For those who are new to APIs, let’s begin by looking closer at what an API is.

What is an API?

At its core, an API acts as an intermediary, facilitating the exchange of data and functionality between applications. One of the most commonly used metaphors for how APIs work goes like this: think of an API as a waiter in a restaurant: you (the client) place an order (a request), the waiter communicates your order to the kitchen (the server), and then brings back your food (the response). Similarly, an API allows one application to request data or services from another and then receive the corresponding response. Different API endpoints, such as a** /accounts** and /users endpoint, would return different kinds of data. Requests like GET, POST, PUT, and PATCH can be made to these specific endpoints depending on the function of the request, such as a GET to retrieve data vs. a POST to create data.

Definition and purpose of APIs

The acronym API stands for Application Programming Interface. Each time you use an app like Facebook, send an instant message, or check the weather on your phone, you’re using an API.

The purpose of an API is to simplify the development of applications by abstracting the underlying complexity. Instead of having to build everything from scratch, developers can leverage existing APIs to access data and functionality from other applications. This not only saves time and resources but also fosters innovation by enabling developers to build upon the work of others. They are also used internally as well, allowing various tiers within an application architecture to communicate with each other.

Brief history and evolution of APIs

APIs have been around for decades, but their popularity has exploded in recent years with the rise of web development and mobile apps. In the early days, APIs were primarily used for internal communication between different components of a single application. However, as the internet grew, APIs began to be used for external communication between different applications.

The evolution of APIs can be traced through various stages, from early proprietary interfaces to the modern RESTful APIs that dominate most API interactions we see today. This evolution has been driven by a desire for greater standardization, flexibility, and ease of use. As a result, APIs have become more accessible to developers, leading to an explosion of API endpoints that developers have access to.

API Types and Protocols

Just like there are different ways to communicate in the human world (spoken language, written language, sign language, etc.), there are also different ways for APIs to communicate. These communication methods are known as protocols. Different API types are designed to address specific use cases and optimize data exchange in various scenarios. Let’s explore some of the most common API types and their associated protocols:

REST APIs

REST APIs are the most popular type of API used on the web today. They adhere to the principles of REST architectural style, which emphasizes simplicity, scalability, and statelessness. REST APIs use standard HTTP methods (GET, POST, PUT, DELETE) to interact with resources, making them relatively easy to understand and implement.

GET: Retrieves data from a server. The GET API method is utilized to access resources and specific data from a server, such as retrieving a list of users or specific user data from an API endpoint.
POST: Creates a new resource on a server.
PUT: Updates an existing resource on a server.
DELETE: Deletes a resource from a server.

REST APIs are widely used for building web services, mobile apps, and other types of applications that need to interact with data over the internet. Much of the time, when developers refer to APIs, they are referring to RESTful APIs.

SOAP APIs

SOAP APIs are a more formal and structured type of API compared to REST APIs. They rely on XML for data exchange and use a strict set of rules and protocols for communication. This can make SOAP APIs more secure and reliable than REST APIs, but also more complex to implement. SOAP APIs are still commonly used for enterprise applications where security and reliability are paramount.

GraphQL APIs

GraphQL is a relatively new type of API that was developed by Facebook. It allows clients to request exactly the data they need, nothing more and nothing less. This can be a significant advantage over REST APIs, which often return more data than is necessary (known as over-fetching), leading to slower performance. GraphQL APIs are becoming increasingly popular for building modern web and mobile applications.

Webhook APIs

Webhooks are a way for one application to notify another application when a specific event occurs. For example, a webhook can be used to notify a payment processing application when a new payment is made, such is the case with Stripe. This allows applications to subscribe and react to events in real time, which can be important for many types of applications.

RPC APIs

RPC APIs allow one application to call a function or procedure in another application. This can be useful for building distributed systems, where different components of the system are running on different machines. RPC APIs are often used for internal communication between different components of a system.

Understanding the different types of APIs and their protocols is crucial for choosing the right type of API for your application. The best type of API for your project will depend on your specific use case and the requirements of your application.

Understanding HTTP Methods

When interacting with RESTful APIs (which, as we discussed, are the most common type), we utilize HTTP methods to perform various operations on the resources they expose. These methods are the verbs in our API communication language, telling the server what action we want to take when calling the endpoint.

HTTP Method Characteristics

Before diving into each method, let’s understand some key characteristics:

Safe Methods (GET, HEAD, OPTIONS)

Read-Only: Safe methods are designed for retrieving data without modifying the state of the server. They should have no side effects.
GET: The most common method for fetching data. It requests a representation of the specified resource.
HEAD: Similar to GET, but only returns the headers of the HTTP response (useful for checking metadata without downloading the entire resource).
OPTIONS: Used to discover the communication options available for a resource (e.g., which HTTP methods are supported).

Idempotent Methods (PUT, DELETE, PATCH)

Repeatable: Idempotent methods can be called multiple times without changing the result beyond the initial application.
PUT: Replaces the entire resource with the data provided in the request body.
DELETE: Removes the specified resource.
PATCH: Partially modifies a resource, updating only the fields specified in the request body.

You’ll likely notice that the HTTP POST method is not listed under either of the above groupings. Since POST is used to create new subordinate resources within a collection of resources, it is neither safe nor idempotent, meaning invoking two identical POST requests will result in two different resources.

HTTP Methods in Depth

Now, let’s explore each API method in more detail:

GET Method

Retrieving data without modifying it

The GET method is the workhorse of API interactions. It’s used to fetch data from a server without causing any changes. Here’s how it typically works:

Client Request: The client sends a GET request to a specific endpoint (e.g., /users/123).
Server Response: The server processes the request, locates the resource (if it exists), and returns a representation of the resource’s current state in the response body.

Example: A GET request to a /products endpoint might return a list of all available products in a JSON format.

POST Method

Creating new resources

The POST method is used to create new resources on the server. Here’s the general flow:

Client Request: The client sends a POST request to an endpoint (e.g., /orders).
Request Body: The request body contains the data for the new resource (e.g., order details like items, quantities, and shipping address).
Server Response: The server processes the request, creates the new resource, and usually returns the details of the newly created resource in the response body.

Example: A POST request to /users with user details in the body might create a new user account.

PUT Method

Updating existing resources

The PUT method is designed to completely replace an existing resource with the data provided in the request body.

Client Request: The client sends a PUT request to a specific resource endpoint (e.g., /products/456).
Request Body: The body contains the complete representation of the updated resource.
Server Response: The server replaces the existing resource with the new data and usually returns the updated resource representation or a success status code.

Example: A PUT request to /users/123 with updated user information would overwrite the existing user data entirely.

PATCH Method

Partially updating existing resources

The PATCH method is used to update an existing resource.
PATCH enables clients to update specific properties on a resource without overwriting others.

DELETE Method

Deleting resources

The PATCH method provides a more fine-grained approach to updates. Instead of replacing the entire resource, it allows modifying specific fields.

Client Request: The client sends a PATCH request to a resource endpoint.
Request Body: The body contains a set of instructions (usually in a JSON Patch format) describing the changes to be applied.
Server Response: The server applies the changes and returns the updated resource or a success code.

Example: A PATCH request to /users/123 could include instructions to change only the user’s email address, leaving other fields untouched.

Conclusion

When it comes to building and using RESTful APIs, understanding how these different HTTP/API methods work is crucial. These methods, whether GET, POST, PUT, PATCH, or DELETE, are the verbs that drive communication between applications, enabling them to exchange data and functionality seamlessly.

By understanding API methods, you can use this knowledge to:

Build robust applications: Create interconnected systems that leverage the strengths of different software components.
Enhance user experiences: Deliver smooth interactions and informative feedback through effective error handling and status codes.
Safeguard your data: Implement authentication and authorization to protect sensitive information from unauthorized access.

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API Analytics , API Monitoring , Best Practices

Dylan Frankcom

Developer Advocate at Moesif

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