Embracing an API-First approach: The bedrock of modern development

Published January 31, 2024. 3 min read

Deepak Kumar, Software Engineer, Enlume

The API-first approach revolutionizes software development, advocating the creation of APIs before specific applications. It prioritizes designing self-contained APIs and defining precise specifications early on to establish a robust foundation for scalable systems. This methodology encourages parallel front-end and back-end development by leveraging standardized API blueprints. However, managing changes in established APIs can be challenging, especially in microservices. To address this, we drew inspiration from API-first principles, generating an OpenAPI specification from server-side routes. This blueprint, stored in a registry, facilitates seamless development by aligning stakeholders with any API contract alterations through precise versioning and releases.

Simplifying API interaction: The power of code generation

In the realm of software development, APIs form the bridge between diverse applications and external services. Whether crafting a web application, mobile app, or any software relying on external data or functionalities, the integration often necessitates HTTP requests to APIs. Writing code for these interactions can be both time-consuming and error-prone. However, a transformative solution exists in the automated generation of clients from Open API (swagger) specifications.

API client generation

API client generation is a dynamic process that automates the creation of code responsible for executing HTTP requests towards an API. Rather than painstakingly handcrafting code to handle requests and manage responses, this approach relies on defining the API structure. API client generation need not be limited to the client side; it extends to both frontend and backend development. We write an 'Open API specification' through which we generate API clients and associated types/models/objects. Subsequently, a code generation tool interprets this structure to produce the necessary code. This methodology thrives when there's a well-documented API contract in place.

API client generation with Swagger/OpenAPI

Suppose you have an OpenAPI specification file (swagger.yaml) describing your API. You can use Swagger Codegen to generate a client.

Generate API client:

There are several tools available for generating API clients from OpenAPI specifications. One popular tool is openapi-generator-cli. Install it globally using npm:

After installation, you can generate the API client using the following command:

Replace path/to/swagger.json with the path to your Swagger or OpenAPI specification file, and output-directory with the desired output directory for the generated API client.

Use the generated API client in JavaScript:

Once the client is generated, you can use it in your JavaScript code. The generated code typically includes functions for making API requests based on the defined endpoints. Here's a simple example:

This is a basic example, and the actual usage may vary depending on the features and options provided by the generated client.An API-first approach with tools like Swagger not only streamlines the development process by fostering a clear understanding of your API's structure and functionality but also facilitates the generation of efficient, maintainable API clients. By prioritizing a well-defined API at the outset of your project, you set the foundation for robust applications that seamlessly integrate with external services, ultimately leading to enhanced scalability and developer productivity

The multifaceted benefits

1. Consistency ensured Generated clients rigorously adhere to the predefined API structure, markedly mitigating the risk of inconsistencies within your codebase.2. Time efficiency unleashed Manually composing API code can consume substantial development time. Code generation liberates developers from this arduous task, significantly expediting development.3. Error reduction Human errors are inherent in manual coding. Due to its automated nature, generated code is inherently less susceptible to typos and other human-induced mistakes.4. Maintenance made easy The fluid nature of APIs often necessitates changes or evolution. With code generation, adapting to these alterations becomes seamless. Regenerating the API client ensures synchronization with the evolving API, thereby simplifying maintenance.

Tools and techniques at your disposal

1. OpenAPI/Swagger For APIs documented using OpenAPI or Swagger, tools like Swagger Codegen prove invaluable. They facilitate the generation of clients in various programming languages.2. Language-Specific Generators Many programming languages boost libraries and tools specifically designed to generate REST API clients based on either API documentation or code annotations.

Navigating the process

1. Define the API contract Defining the API contract marks the genesis of a successful code-generation process. This involves a meticulous examination of the API's architecture, outlining endpoints, methods, and the underlying data structures. By mapping out these elements comprehensively, developers establish a concrete blueprint that serves as a guiding framework for subsequent stages.Key considerations:

Endpoints and Methods: Delineate the various endpoints the API offers, specifying the methods (GET, POST, PUT, DELETE) associated with each.
Data Structures: Define the structure of data payloads exchanged between the client and the API, ensuring clarity in data handling.

2. Select an appropriate code generation tool Choosing the right code generation tool significantly influences the efficiency and effectiveness of the API integration process. Factors such as API type, programming language, scalability, community support, and compatibility with the project's tech stack play pivotal roles in tool selection.Considerations when selecting a tool:

API type and documentation: Ensure the chosen tool aligns with the API documentation format, such as OpenAPI/Swagger, etc.
Community support and scalability: Assess the tool's community involvement and its ability to scale as your project grows.

3. Generate the API clients Utilizing the selected code generation tool automatically generates the API clients based on the defined API contract. This step involves the translation of the structured API contract into functional code that can effectively communicate with the API endpoints.Validation and alignment:

Code Review against API Contract: Thoroughly review the generated client to ensure its alignment with the previously defined API contract.
Verification of Endpoints and Methods: Validate that the generated client accurately represents all specified endpoints and methods.

4. Configuration Configure the generated API client to align with the specific requirements and settings of the API and your application. This involves setting up essential parameters such as the API base URL, authentication tokens, security measures, and strategies for handling potential errors.Essential Configuration Settings:

API Base URL and Authentication: Set the base URL to direct requests correctly and incorporate appropriate authentication mechanisms for secure communication.
Security Measures and Error Handling: Implement necessary security protocols and devise strategies to handle errors gracefully.

5. Integration With the API clients generated and configured, seamlessly integrate it within your application's codebase. Execute comprehensive tests to validate the functionality of the integrated API client, ensuring it seamlessly interacts with the application's core logic.Testing and validation:

Functional testing: conduct rigorous tests to verify that the generated client executes API requests accurately and returns expected responses.

In conclusion

Embracing the practice of generating API clients from Open API (swagger) specifications revolutionizes the consumption of APIs. It champions consistency, curtails errors, and accelerates development, empowering developers to interact seamlessly with external services. This enables software to connect, extend, and innovate, making our lives more convenient and our technology more powerful. Whether you're a developer or a business owner, this methodology quietly influences the tech environment. Understanding how important and useful this method is essential for succeeding in the constantly changing world of technology.Happy API exploration!