#Choosing an adapter

An adapter connects your app to an HTTP server. Your routes, middlewares, errors and tests do not depend on it: switching from one adapter to another changes one line of createApp().

// Express
const app = await createApp({ adapter: expressAdapter(), routers })
// Fastify
const app = await createApp({ adapter: fastifyAdapter(), routers })
// Hono, on Node.js
const app = await createApp({ adapter: honoAdapter(), routers })

#Compared

#Which one?

• Your team knows one of them, or your app already runs on it: take that one. Mount Dotpress on your existing application, next to its native routes, and move them over time.
• You need middlewares or plugins of a specific ecosystem (helmet, @fastify/rate-limit, Hono middlewares…): take the server of that ecosystem.
• The API runs on AWS Lambda: take Hono for the smallest bundle, or Fastify if you need its plugins.
• No preference: any of them works the same with Dotpress. You can change your mind later.

Coming from Dotpress 1, which ran on Express: keep Express to migrate in small steps.

#The same behavior everywhere

Whatever the adapter, Dotpress itself:

• matches the routes, with the same rules: case-sensitive, static segments before parameters, trailing slashes ignored, 405 with an Allow header;
• reads and parses the bodies: JSON, forms, text, multipart uploads, with the same size limit and errors;
• builds the responses, including streams and Server-Sent Events;
• formats the errors, including the client errors of native middlewares (a 4xx keeps its status).

Every adapter passes the same conformance test suite of @dotpress/testing, which covers routing, parsing, validation, errors, middlewares and responses.

#Common options

The app also gives access to the server:

• app.native() returns the native application (Express app, Fastify instance, Hono app);
• adapter.server() returns the Node.js HTTP server started by listen();
• ctx.raw is the native request (or context), as an escape hatch in a route.

app.close() waits for the pending requests, closes the responses being streamed, then runs the onClose hooks of the plugins: call it on SIGTERM for a graceful shutdown (see Node.js and containers).

#In tests

The memory adapter of @dotpress/testing is an adapter too: it runs the requests in memory, without a port. See Testing.