n. An explanation or critical interpretation of a text, especially an API definition document.
-- No dictionary ever
This library implements a framework-agnostic server side implementation of OpenAPI 3.x.
Exegesis is a library for implementing server-side OpenAPI 3.x The library has been written in such a way that hopefully it will also be used to implement future versions of OpenAPI, or possibly even other API description standards altogether.
You probably don't want to be using this library directly. Have a look at:
- exegesis-express - Middleware for serving OpenAPI 3.x APIs from express or connect.
- exegesis-koa - Middleware for serving OpenAPI 3.x APIs from koa.
- Full support for OpenAPI 3.x.x (see issues tagged with conformance for areas which could use some improvement).
- Built in support for "application/json" and "application/x-www-form-urlencoded" requests
- Can use express body parser middlewares
- Response validation
- Authentication support
- Plugins allow easy extensibility
- Easy support for validating custom formats
Check out the tutorial here.
This function takes an API document and a set of options, and returns a connect-style middleware function which will execute the API.
openApiDoc is either a path to your openapi.yaml or openapi.json file,
or it can be a JSON object with the contents of your OpenAPI document. This
should have the x-exegesis-controller
extension defined on any paths you want to be able to access.
options is described in detail here. At a
minimum, you'll probably want to provide options.controllers, a path to where
your controller modules
can be found. If you have any security requirements defined, you'll also
want to pass in some authenticators.
To enable response validation, you'll want to provide a validation callback
function via onResponseValidationError().
Exegesis's functionality can also be extended using plugins,
which run on every request. Plugins let you add functionality like
role base authorization,
or CORS.
This function is similar to compileApi; it takes an API document and a set of
options,
and returns a "runner". The runner is a function runner(req, res), which takes
in a standard node HTTP request and response. It will not modify the response,
however. Instead it returns (either via callback or Promise) and HttpResult
object. This is a {headers, status, body} object, where body is a readable
stream, read to be piped to the response.
A convenience function for writing an HttpResult from a runner out to the
response.
import * as path from 'path';
import * as http from 'http';
import * as exegesis from 'exegesis';
// See https://github.com/exegesis-js/exegesis/blob/master/docs/Options.md
const options = {
controllers: path.resolve(__dirname, './src/controllers'),
};
// `compileApi()` can either be used with a callback, or if none is provided,
// will return a Promise.
exegesis.compileApi(
path.resolve(__dirname, './openapi/openapi.yaml'),
options,
(err, middleware) => {
if (err) {
console.error('Error creating middleware', err.stack);
process.exit(1);
}
const server = http.createServer((req, res) =>
middleware(req, res, (err) => {
if (err) {
res.writeHead(err.status || 500);
res.end(`Internal error: ${err.message}`);
} else {
res.writeHead(404);
res.end();
}
})
);
server.listen(3000);
}
);Internally, when you "compile" an API, Exegesis produces an
ApiInterface object.
This is an object that, given a method, url, and headers, returns a
resolvedOperation -
essentially a collection of functions that will parse and validate the body and
parameters, has the controller that executes the functionality, etc... The only
current implementation for an ApiInterface is the
oas3/OpenApi class.
Essentially this class's job is to take in an OpenAPI 3.x.x document, and turn it
an ApiInterface that Exegesis can use. In theory, however, we could parse some
other API document format, produce an ApiInterface, and Exegsis would still be
able to run it.