What does it bring us?<\/p>\n\n\n\n
- \n
- API description, definition of parameter schemes on input and output<\/li>\n\n\n\n
- automatically generated documentation, which also serves as a test of requests<\/li>\n\n\n\n
- and depending on the framework used, an automatic router and an input validator<\/li>\n<\/ul>\n\n\n\n
And precisely the last point is the problem in node.js. We use the koa.js<\/a> library as the basis of the http server. It has almost twice the performance<\/a> of the express. It has a nice middleware scheme. It uses generators and asynchronous code. It\u2019s easy to implement and doesn’t layer unnecessary ballast over the native http(s) module.<\/p>\n\n\n\n
But we searched in vain for a library that would take the OpenAPI specification on one hand, the Koa application on the other, and combine it with all the advantages. And so we made a small, 500-line library ourselves. It’s a compilation of several libraries, each of which performs its function and does it well.<\/p>\n\n\n\n
Koa + OAS3 = KOAS3<\/h2>\n\n\n\n
With a separate library, we killed several flies with one blow:<\/p>\n\n\n\n
- \n
- The library will create a router that you will deploy to an existing Koa application as middleware. This way you can integrate it among other already existing routers and middlewares, or make only a part of the application using OpenAPI. This is useful if you are dealing with a problem that doesn’t support OAS3, or for example, when you need to attach a stream to a URL or a Websocket server.<\/li>\n\n\n\n
- The definition of security (authentication and authorization) is taken from OpenAPI and each request is automatically protected as specified in OAS3. Of course, you have to write the individual security handlers yourself ?<\/li>\n\n\n\n
- Each request parameter is checked and validated against the specification. So in the controller, you don’t have to worry about whether the user ID arrived as an integer or a string. If you specified it as an integer, it is 100 % integer, otherwise KOAS3 will return an error http response 400 Bad Request.<\/li>\n\n\n\n
- As a bonus, KOAS3 will create a route on which it will attach a neat documentation, usually on \/docs – for example, a specification for our Pages application.
How is it implemented? Everything you need can be found on the npm koas3 package page<\/a>.<\/li>\n<\/ol>\n\n\n
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