The RESTful Application Programming Interface (API) was introduced in the year 2000 itself but we still don’t have any set guidelines or standards for the development of APIs to date. Over the years, developers have tried various ways to create better REST API solutions. Some of them hit the mark while others missed it. The software development industry has filtered the best practices for RESTful API design in the past 18-19 years.
Are you ready to build better APIs?
The web is full of opinions regarding API designs but most of them are just academic discussions full of subjective interpretations instead of what actually makes sense. Keeping all the subjectivity aside, here are some of the key factors and requirements that will help you build better APIs:
- Web standards must be used strategically i.e. as and when required.
- It must be user-friendly and easily accessible.
- The design must be simple, intuitive, and consistent yet effective.
- It should have the flexibility to adopt new updates.
- The API should be efficient and maintain a balance with the user's needs.
Best Practices & Guidelines to Design RESTful API
We will discuss them one by one and will try to understand them better. Let’s look at the things to be kept in mind before you build an API:
1. Naming & Conventions
The API must promote clear usage. Use as many words as possible to avoid any case of ambiguity for the person who is reading the code, especially when a name is used. Each word contained in a name must deliver salient information wherever it’s used. Rather than writing the type of constraint, assign names to all the variables, parameters, and associated types as per their roles.
Use methods and properties of free functions and follow case conventions. Methods might have the same base name when they have the same basic meaning, or they function in separate domains.
2. Use JSON
Depending upon the type of your application and the purpose you need the API for, REST allows a developer to use various output formats such as plain text, JSON, CSV, RSS, HTML, and XML. JSON is an ideal choice if you have a public-facing service and you want to make it accessible to the users through REST API in the form of the data format used for communication, in both the payload and response. Moreover, the generic MIME nature of JSON makes it easier to be used.
3. Use RESTful URLs and actions
RESTful principles such as separating your API into logical resources, have gained wide popularity and have been majorly adopted by app development companies. These resources make use of HTTP requests to get manipulated where various methods like GET, POST, DELETE, PUT, PATCH have specific meanings.
4. Use resource nesting to show relations of hierarchy
All the resource objects have a functional hierarchy and they are related to each other. For instance, in a store, we have customers and their orders, both interrelated. It’s a good idea to restrict the nesting to one level in REST API. Too many nested levels increase complexity and decrease efficiency. However, the same output can be achieved by filtering.
5. Error Handling
While developing an API, correct error handling is one of the practices to be focused upon out of which standard HTTP error handling is the most important. There are almost 71 different HTTP status codes available for use which are well defined and can easily be recognized. Correct error handling of the HTTP statuses is enough, but it is always better to provide extra information and a detailed explanation for a good user experience.
6. Filtering, sorting, paging, and field selection
Some of the most important features of using an API are filtering, sorting, and paging. Filtering helps to narrow down the query results using specific parameters such as date, location, etc. Sorting stands for arranging the results in a particular order i.e. ascending or descending based on the chosen parameter (say date). Paging filters the results and displays a limited number of matching items by deciding the range of the results to be shown. Field selection allows you to use various parameters to specify which ones you want to see in the results for a certain object.
7. SSL everywhere - all the time
Using SSL reduces the chances of cyber-attacks and assures security as your API can be accessed from anywhere across the globe and most of those networks aren’t secured or encrypted. It guarantees encrypted communications and ensures authentication i.e. you can access it with simple tokens without signing every API request.
It allows you to make changes to your data structure even the ones which are irreversible. In cases when you have to manage multiple APIs it helps you implement changes and improve the service simultaneously. You can either implement the version in the request header or in the endpoint URI as you find apt.
9. API endpoint
An API endpoint is defined as a point at which the API connects with the software program. In an API endpoint, the resource should always be plural, and any instance of the resource can be accessed by passing the ID in the URL. In short, the paths must contain plural forms of the resources and the type of action to be performed is defined by the HTTP method.
10. HTTP status codes
There are some meaningful status codes that your API can return. These codes can be used to help API users in routing their responses. Some of the useful status codes are 200 (OK), 201 (Created), 204 (No Content), 304 (Not Modified), 400 (Bad Request), etc.
There are built-in frameworks offered by HTTP for caching. You need to include some additional outbound response headers and have to validate them on receiving inbound request headers. There are two approaches to the same. One is the ETag in which you must include an HTTP header ETag having a hash or checksum of the representation while generating a response and the other one is last modified which works similar to ETag along with making use of timestamps.
An ideal RESTful API is stateless i.e. the request authentication doesn’t rely upon cookies or sessions. Every request must with some authentication credentials associated with it. The authentication credentials can easily be simplified using SSL, to a random-access token that gets delivered to the user. It’s very easily accessible and explorable via a browser.
13. Overriding the HTTP method
The Application Programming Interface (API) needs a way to override the HTTP methods to increase the accessibility to clients who can only work with simple GET and POST requests. It doesn’t follow any high standards but the conventional one of accepting the request header X-HTTP-Method-Override with a string value having one of PUT, DELETE, or PATCH.
It’s done to handle the responses easily. A result of having hundreds of thousands of pages would be a complex task to go through while we can simplify it by explicitly setting a limit to ensure the desired number of results as per the limiting parameter.
A good process for RESTful API design isn’t only about working under technical constraints but also about providing the users with a good experience by making the API design easily accessible and usable. It becomes difficult to choose the one practice when there is plenty of options are available, but every method has its own usability and relevance. One just needs to evaluate their needs and pick the one which fits in well with his requirements.