Since its release in 2011, the Swagger API framework has rapidly grown in popularity among mobile app developers. The framework supports practically all popular programming languages as well as deployment environments, enhancing its usability. According to users, Swagger represents an improvement over both the manual API data maintenance method, as well as Web Application Description Languages (WADL). In September 2014, Swagger 2.0 was launched – and at present, it is easily the largest available repository for APIs in the world. Let us here take a look at some interesting things to know about the Swagger API framework:

1. What exactly is Swagger? 

   Swagger is a huge collection of tools (integrated as an ecosystem), which is arranged around a formal specification. The specification represents a standard of REST (representational state transfer) APIs. The tools, on the other hand, include coding libraries (low level), commercial API management frameworks, and user interface solutions. In a nutshell, Swagger provides a language-independent interface for REST APIs, which is both human-readable and machine-readable.

2. Why is Swagger preferred by developers? 

   Most apps have to be connected to a web-supported cloud backend, and for that, developers need to use APIs extensively. Swagger offers a convenient way for coders to document these APIs. It is easily a better option than having to manually maintain API information on either a HTML page or a text document (which won’t be machine-readable either). Web Application Description Languages (WADL), on the other hand, lose out on the human-readability front. Swagger can be understood by human users as well as machines – and not surprisingly, software and app developers from across the world use it for API data maintenance.

3. Is Swagger open-source? 

   Swagger has been a completely open-source API framework from the very outset. It serves as a detailed representation of RESTful APIs (although all the RESTful rules are not followed), is easily discoverable, and also generates client-side SDKs. The highly interactive documentation also makes Swagger all the more developer-friendly.

4. How can you start using Swagger? 

   There are two alternative approaches for that. App developers can either go for the so-called ‘bottom-up’ approach, where Swagger definitions have to be created – either manually or with the help of node.js or JAX-RS, or any of the other frameworks that are supported. The ‘top down’ approach involves creation of the same Swagger definition with the help of the Swagger Editor. For server-side implementation, the resources within Swagger Codegen have to be used. Both methods are fairly simple – and the final choice depends on what any particular app maker is comfortable with.

5. How to migrate from Swagger 1.x to Swagger 2.0? 

   Swagger 2.0 has a lot of handy new features for developers (more on that later). All that coders, who are already using Swagger 1.2 (or any of the other older versions), need to do is use the Swagger Converter to migrate to the latest version of the framework. While converting code specs, either the ‘swagger-spec-converter’ or the ‘swagger-tools’ command line tool has to be used. Keep in mind that, unlike Swagger 1.x (which has two separate files), Swagger 2.0 has a single file.

6. How is build and deployment managed in Swagger? 

   Swagger 1.5 introduced the io.swagger package. All the artifacts used in Swagger can be found in Maven Central – and for build and deployment, the API framework uses Apache Maven. Systems like Gradle and Ivy (apart from, of course, Maven) can handle the Maven dependencies inside the Swagger tool. In Swagger-Core, ‘io.swagger’ remains the groupID name, for all the dependencies.

Note: In JAX-RS, three artifacts are used by Swagger. These are ‘swagger-jersey-jaxrs’, ‘swagger-jaxrs’ and ‘swagger-jersey2-jaxrs’ (on version 2.0).

7. What is the Swagger Editor? 

   Those who make mobile apps and use Swagger can edit/review API specifications within the browser itself, in the Swagger Editor. In addition, the Editor also allows users to view documentations on a real-time basis. Code generations and other commonly used Swagger toolings can be used with the Swagger JSON descriptions. Swagger Editor supports the YAML data serialization language (please note that it is not a markup language).

8. What’s there for API Consumers? 

   The ‘top down’ and ‘bottom up’ approaches for getting started on Swagger were for API Providers. Let’s turn our attentions towards the other set of users – the API Consumers. For them, the API framework has the online Swagger UI – that uses Swagger Codegen to create selected client libraries. APIs can be explored with Swagger UI as well. Integrating with APIs that have Swagger definitions is a common requirement, and this functionality is of help regarding that.

9. What are the steps to integrate Swagger documentation in your app? 

   For seamless integration of Swagger documents in an application, developers have to follow three steps. First, all the Swagger dependencies have to be added in the project. Manual addition of dependencies is necessary for projects that do not support Maven dependencies. Next, Swagger has to be linked up with the actual application configuration (JAX-RS). Once that is done, both /swagger.yaml and /swagger.json will become accessible. Finally, the Swagger framework has to be configured and initialized.

Note: Implementation can be for RESTEasy 2.x, Jersey 1.x and 2.x, or Mule projects.

        10. What’s new in Swagger 2.0? 

Path-level parameter declaration, vendor extensions (with metadata) and smarter operations grouping feature among the most important additions in Swagger 2.0. Software and app developers have the option of adding License Object and/or Contact Object to the Info object, as well as describe Headers within responses. The second iteration of Swagger also supports API First development methodology, driven by node.js REST API environments (this feature has been added by Apigee). The format has been made compatible with JSON and YAML, for greater user-convenience. Well over 30 tools support the Swagger 2.0 framework – Swagger Parser, Swagger-JS, Swagger Validator, Swagger-UI, Swagger Codegen and Swagger-Core being some of them.

Note: Swagger is now more commonly referred to as the Open API Specification. It was given to the Open API Initiative (OAI) in January 2016.

        11. Why should developers use Swagger? 

We have already mentioned that Swagger is the largest API network at present. It does away with the need for accessing source codes, network traffic monitoring and other documentations, when developers are trying to find and understand the REST API interface service. Uncertainties and risks of errors become minimal when Swagger is correctly implemented in a project – since the need for implementation logic is almost nil, while interacting with remote service. Both commercial vendors and open-source projects are served by Swagger.

      12. What is the Restlet Studio for API definitions all about?

Restlet, another founding member of OAI, offers Restlet Studio – a user-friendly visual editor that makes the task of authoring API contracts easier than ever before. It stores all the Swagger API definitions, generates the required skeleton code, and comes with a built-in API definition translator (for different API formats). With the visual editing feature, app developers need not learn everything about all the Swagger syntax either – a tour of the UI serves the purpose.

The open-source Swagger specification is present under ASL 2.0, and it is a definitive guide on how responses, paths, parameters, and all other things should be correctly defined. Some of the biggest names in the tech domain – from PayPal and Microsoft, to Intuit and Apigee – use the Swagger service for their RESTful APIs. With plenty of supported tools and loads of useful resources, Swagger is absolutely a must-have API framework for mobile developers.