A focused framework for creating RESTful JSON services across various JavaScript and TypeScript runtime environments including Deno runtime, Deno Deploy, Node.js, Bun and Cloudflare Workers.
It focuses on providing a router which handles inbound requests and makes it trivial to respond to those requests with JSON. It also provides several other features which make creating API servers with acorn production ready. acorn is a focused framework for creating RESTful JSON services across
acorn is designed to work on many different JavaScript and TypeScript runtimes, including Deno, Node.js, Bun, and Cloudflare Workers. Basic usage requires installing acorn to your project and then creating a router to handle requests.
To install acorn for Deno, you can install it via the Deno runtime CLI:
deno add jsr:@oak/acorn
To install acorn for Node.js or Cloudflare Workers, you can install it via your preferred package manager.
npx jsr add @oak/acorn
yarn dlx jsr add @oak/acorn
pnpm dlx jsr add @oak/acorn
To install acorn for Bun, you can install it via the Bun runtime CLI:
bunx jsr add @oak/acorn
Basic usage of acorn for Deno, Node.js, and Bun is the same. You import the
Router, create an instance of it, register routes on the router, and then
called the .listen() method on the router to start listening for requests:
import { Router } from "@oak/acorn";
const router = new Router();
router.get("/", () => ({ hello: "world" }));
router.listen({ port: 3000 });Basic usage for Cloudflare Workers requires exporting a fetch handler which is integrated into the router, and therefore you export the router as the default export of the module:
import { Router } from "@oak/acorn";
const router = new Router();
router.get("/", () => ({ hello: "world" }));
export default router;The Router is the core of acorn and is responsible for handling inbound
requests and routing them to the appropriate handler. The router provides
methods for registering routes for different HTTP methods and handling requests
for those routes.
The router provides several automatic behaviors which are designed to make
creating RESTful JSON services easier. These behaviors include handling
404 Not Found responses, 405 Method Not Allowed responses, and providing a
default response for OPTIONS requests.
When a request is received by the router and no route is matched, the router
will send a 404 Not Found response to the client. This is the default behavior
of the router and can be overridden by providing a onNotFound hook to the
router.
When a request is received by the router and a route is matched but there is no
handler for the method of the request, the router will send a
405 Method Not Allowed response to the client which will provide the allowed
methods. This is the default behavior of the router and can be overridden by
providing a status handler.
When a request is received by the router and the method of the request is
OPTIONS, the router will send a response to the client with the allowed
methods for the route. This is the default behavior of the router and can be
overridden by providing an options() route.
The Context is the object passed to route handlers and provides information
about the request and runtime environment. The context object provides access to
the Request object as well as other useful properties and methods for handling
requests.
The network address of the originator of the request as presented to the runtime environment.
The cookies object which can be used to get and set cookies for the request. If encryptions keys are provided to the router, the cookies will be cryptographically verified and signed to ensure their integrity.
The environment variables available to the runtime environment. This assists in providing access to the environment variables for the runtime environment without having to code specifically for each runtime environment.
A unique identifier for the request event. This can be useful for logging and tracking requests.
The parameters extracted from the URL path by the router.
The Fetch API standard Request object which should be handled.
The headers that will be sent with the response. This will be merged with other headers to finalize the reponse.
The URL object representing the URL of the request.
A parsed version of the User-Agent header from the request. This can be used
to determine the type of client making the request.
A method which returns a promise that resolves with the body of the request assumed to be JSON. If the body is not JSON, an error will be thrown. If a body schema is provided to the route, the body will be validated against that schema before being returned.
A method which throws a 409 Conflict error and takes an optional message and
optional cause.
A method which returns a Response with a 201 Created status code. The method
takes the body of the response and an optional object with options for the
response. If a location property is provided in the options, the response will
include a Location header with the value of the location.
If locationParams is provided in the options, the location will be
interpolated with the parameters provided.
A method which throws a 404 Not Found error and takes an optional message and
optional cause.
A method which returns a promise that resolves with the query parameters of the request. If a query parameter schema is provided to the route, the query parameters will be validated against that schema before being returned.
A method which sends a redirect response to the client. The method takes a
location and an optional init object with options for the response. If the
location is a path with parameters, the params object can be provided to
interpolate the parameters into the URL.
A method which can be used to throw an HTTP error which will be caught by the router and handled appropriately. The method takes a status code and an optional message which will be sent to the client.
A method which returns a Response with a 201 Created status code. The method
takes the body of the response and an optional object with options for the
response.
This is an appropriate response when a POST request is made to a resource
collection and the resource is created successfully. The options should be
included with a location property set to the URL of the created resource. The
params property can be used to provide parameters to the URL. For example if
location is /books/:id and params is { id: 1 } the URL will be
/books/1.
A method which throws a 409 Conflict error and takes an optional message and
optional cause.
This is an appropriate response when a PUT request is made to a resource that
cannot be updated because it is in a state that conflicts with the request.
A method which starts sending server-sent events to the client. This method
returns a ServerSentEventTarget which can be used to dispatch events to the
client.
A method which can be used to upgrade the request to a WebSocket connection.
When the request is upgraded, the request will be handled as a web socket
connection and the method will return a WebSocket which can be used to
communicate with the client.
Note: This method is only available in the Deno runtime and Deno Deploy currently. If you call this method in a different runtime, an error will be thrown.
The RouteHandler is the function which is called when a route is matched by
the router. The handler is passed the Context object and is expected to return
a response. The response can be a plain object which will be serialized to JSON,
a Response object. The handler can also return undefined if the handler
wishes to return a no content response. The handler can also return a promise
which resolves with any of the above.
Routes can be registered on the router using the various methods provided by the
router. The most common methods are get(), post(), put(), patch(), and
delete(). In addition options() and head() are provided.
The methods take a path pattern and a handler function, and optionally an object
with options for the route (RouteInit). The path pattern is a string which can
include parameters and pattern matching syntax. The handler function is called
when the route is matched and is passed the context object.
For example, to register a route which responds to a GET request:
router.get("/", () => ({ hello: "world" }));The methods also accept a RouteDescriptor object, or a path along with a set
of options (RouteInitWithHandler) which includes the handler function.
For example, to register a route which responds to a POST request:
router.post("/", {
handler: () => ({ hello: "world" }),
});And for a route which responds to a PUT request with the full descriptor:
router.put({
path: "/",
handler: () => ({ hello: "world" }),
});The router provides hooks which can be used to get information about the routing process and to potentially modify the response. The hooks are provided when creating the router and are called at various points in the routing process.
The onRequest hook is called when a request is received by the router. The
RequestEvent object is provided to the hook and can be used to inspect the
request.
The onRequest could invoke the .respond() method on the RequestEvent but
this should be avoided.
As a request is being handled by the router, if no route is matched or the route
handler returns a 404 Not Found response the onNotFound hook is called.
There is a details object which provides the RequestEventbeing handled, any
Response that has been provided (but not yet sent to the client) and the
Route that was matched, if any.
The onNotFound hook can return a response to be sent to the client. If the
hook returns undefined, the router will continue processing the request.
After a request has been processed by the router and a response has been sent to
the client, the onHandled hook is called. The hook is provided with a set of
details which include the RequestEvent, the Response, the Route that was
matched, and the time in milliseconds that the request took to process.
If an unhandled error occurs in a handler, the onError hook is called. The
hook is provided with a set of details which include the RequestEvent, the
Response that was provided, the error that occurred, and the Route that was
matched, if any.
The router can extract parameters from the URL path and provide them to the
route handler. The parameters are extracted from the URL path based on the
pattern matching syntax provided by the
path-to-regexp library. The
parameters are provided to the handler as an object with the parameter names as
the keys and the values as the values.
For example, to register a route which extracts a parameter from the URL path:
router.get("/:name", (ctx) => {
return { hello: ctx.params.name };
});acorn provides a mechanism for observing or modifying the response to a request based on the status of the response. This is done using status handlers which are registered on the router. The status handlers are called when a response is being sent to the client and the status of the response matches the status or status range provided to the handler.
This is intended to be able to provide consistent and customized responses to
status codes across all routes in the router. For example, you could provide a
status handler to handle all 404 Not Found responses and provide a consistent
response to the client:
import { Router } from "@oak/acorn";
import { Status, STATUS_TEXT } from "@oak/commons/status";
const router = new Router();
router.on(Status.NotFound, () => {
return Response.json(
{ error: "Not Found" },
{ status: Status.NotFound, statusText: STATUS_TEXT[Status.NotFound] },
);
});acorn integrates the Valibot library to provide schema validation for query strings, request bodies, and responses. This allows you to define the shape of the data you expect to receive and send and have it validated automatically.
You can provide a schema to the route when registering it on the router. The schema is an object which describes the shape of the data you expect to receive or send. The schema is defined using the Valibot schema definition language.
For example, to define a schema for a request body:
import { Router, v } from "@oak/acorn";
const router = new Router();
router.post("/", () => ({ hello: "world" }), {
schema: {
body: v.object({
name: v.string(),
}),
},
});This ensures that the request body is an object with a name property which is
a string. If the request body does not match this schema, an error will be
thrown and the request will not be processed and a Bad Request response will
be sent to the client.
You can provide an optional invalid handler to the schema which will be called when the schema validation fails. This allows you to provide a custom response to the client when the request does not match the schema.
acorn is designed to make it easy to create RESTful JSON services. The router provides a simple and expressive way to define routes and has several features which make it easy to create production ready services.
acorn provides a mechanism for throwing HTTP errors from route handlers. The
throw() method on the context object can be used to throw an HTTP error. HTTP
errors are caught by the router and handled appropriately. The router will send
a response to the client with the status code and message provided to the
throw() method with the body of the response respecting the content
negotiation headers provided by the client.
If a handler returns undefined, the router will send a 204 No Content
response to the client. This is useful when a request is successful but there is
no content to return to the client.
No content responses are appropriate for PUT or PATCH requests that are
successful but you do not want to return the updated resource to the client.
The created() method on the context object can be used to send a 201 Created
response to the client. This is appropriate when a POST request is made to a
resource collection and the resource is created successfully. The method takes
the body of the response and an optional object with options for the response.
The options should be included with a location property set to the URL of the
created resource. The params property can be used to provide parameters to the
URL. For example if location is /books/:id and params is { id: 1 } the
URL will be /books/1.
The conflict() method on the context object can be used to throw a
409 Conflict error. This is appropriate when a PUT request is made to a
resource that cannot be updated because it is in a state that conflicts with the
request.
If you need to redirect the client to a different URL, you can use the
redirect() method on the context object. This method takes a URL and an
optional status code and will send a redirect response to the client.
In addition, if the location is a path with parameters, you can provide the
params object to the redirect() method which will be used to populate the
parameters in the URL.
acorn integrates the LogTape library to provide logging capabilities for the router and routes.
To enable logging, you can provide a LoggerOptions object on the property
logger to the router when creating it:
const router = new Router({
logger: {
console: { level: "debug" },
},
});Alternatively, you can simply set the logger property to true to log events
at the "WARN" level to the console:
const router = new Router({
logger: true,
});Copyright 2018-2024 the oak authors. All rights reserved. MIT License.