bedrock-express

A bedrock module that integrates express with bedrock to provide a routing framework and other features for writing Web applications. It uses the bedrock event system to emit a number of configuration events that dependent modules may use to add features to a core express server.

Requirements

• node v18+
• npm v9+

Quick Examples

npm install @bedrock/express

import * as bedrock from '@bedrock/core';

bedrock.events.on('bedrock-express.configure.routes', addRoutes);

function addRoutes(app) {
  app.get('/', function(req, res) {
    res.send('Hello World!');
  });
}

Configuration

For documentation on configuration, see config.js.

config.express.session.ttl is was added in version 5.0.0 that should be a number expressing in milliseconds how long a session should last. This can be enforced by a session store on the server as opposed to the client.

config.express.session.ttl defaults to 30 minutes in milliseconds.

This option should be used by express-session storage implementations that can access @bedrock/express configuration options. bedrock-session-mongodb can be used as an example.

How It Works

bedrock-express exposes an express server over TLS, using the bedrock-server module. It takes the approach that most applications built on express set it up in very similar ways. Therefore, bedrock-express sets up a default express server using very common options and middleware, but lets other modules decide which parts to change or turn off. For simple changes, modules can use bedrock.config.express to configure the express server. For more complex changes or to cancel chosen default behavior entirely, modules can use the events that bedrock-express emits.

bedrock-express will begin setting up the express server and emitting its events when the core bedrock.start event is emitted. When the bedrock.ready event is emitted, bedrock-express will attach the express server to the bedrock-server HTTPS server to begin accepting requests.

By default, bedrock-server will only serve requests over HTTPS; if any HTTP requests arrive, they will be redirected to HTTPS. If you want to enable HTTP requests, do the following:

import * as brServer from '@bedrock/server';
import * as brExpress from '@bedrock/express';

// track when bedrock is ready to attach express
bedrock.events.on('bedrock.ready', function() {
  // attach express app to regular http
  brServer.servers.http.on('request', brExpress.requestHandler);
});

Events

bedrock-express emits several events that modules may listen for. Most of these events are emitted during the setup process of a default express server, allowing modules to change only the behavior they are interested in customizing. Every event emitted will pass the express server object as the first parameter to the listener function. The most commonly used event is bedrock-express.configure.routes, which allows modules to attach new routes to express to provide, for example, a REST API.

In version 5.0.0, a fastify compatibility layer was added to add in the transition to fastify, which is a better maintained and more performant http server framework. Some new events were added related to fastify setup.

• bedrock-express.fastify.init
  • Emitted once fastify(-express) is ready and provides access to the fastify instance; before any other setup of the express server.
• bedrock-express.init
  • Emitted before any other setup of the express server.
• bedrock-express.init
  • Emitted before any other setup of the express server.
• bedrock-express.configure.logger
  • Emitted before binding bedrock's logging system to express. By default, the express middleware, morgan, is used to write combined server access information to bedrock's access logger. This event can be used to log server access in another way and/or it can be canceled to prevent logging to bedrock's access logger.
• bedrock-express.configure.bodyParser
  • Emitted before the default body parser is setup. By default, express will parse application/json message bodies into JavaScript objects. It will not parse application/x-www-form-urlencoded as a minor attempt to help prevent CSRF attacks on handlers that expect parsed JSON but may receive parsed application/x-www-form-urlencoded messages instead. Listeners of this event can change default parsing behavior or turn it off by canceling this event.
• bedrock-express.configure.cookieParser
  • Emitted before the default cookie parser is setup. Be default, the express middleware, cookie-parser, is used, configured using the the bedrock.config.express.session.secret configuration value. Listeners can use this event to replace or simply cancel this behavior.
• bedrock-express.configure.session
  • Emitted before the default session handle is setup. By default, the express middleware, express-session, is installed and uses the bedrock.config.express.session configuration object. Listeners can use this event to initialize session storage or to replace or cancel the default session handling behavior entirely.
• bedrock-express.configure.static
  • Emitted before the default static content handler is configured. By default, bedrock-express provides the ability to configure multiple static routes. A handler for each route configuration found in the bedrock.config.express.static array will be registered with express. Route configurations may specify files or entire paths to serve, and whether or not CORS should be enabled. The handlers will be added in the reverse order of the array. This gives priority to route configurations that were pushed onto the array last, should there be more than one handler for a particular route. This means that when a request is received by express that matches a particular route, the handler that will be given the first opportunity to respond will be the last in the array that matches the route. If that handler cannot find a file to send, then the second-to-last handler created with a matching route will be executed, and so forth. The approach allows projects to easily override which static files are sent for a particular route via the configuration system.
• bedrock-express.configure.cache
  • Emitted after bedrock-express.configure.static and before the default cache handler for dynamic content is installed. By default, caching for dynamic content is disabled by setting these headers:
    • Cache-Control: no-cache, no-store, must-revalidate
    • Pragma: no-cache
    • Expires: 0 Listeners may replace and/or cancel this behavior.
• bedrock-express.configure.router
  • Emitted before any routes are added to the default express router.
• bedrock-express.configure.routes
  • Emitted after bedrock-express.configure.router to allow modules to add routes to express. This is the most common event for modules to bind to. A module should attach a listener to this event to expose, for example, a REST API.
• bedrock-express.configure.errorHandlers
  • Emitted after bedrock-express.configure.routes to handle any errors that routes may have generated. Listeners can use this event to attach custom error handlers.
• bedrock-express.configure.unhandledErrorHandler
  • Emitted after bedrock-express.configure.errorHandlers to attach a handler for any unhandled errors. By default, an unhandled error handler is installed that changes its behavior based on whether or not bedrock.config.express.dumpExceptions is true. If it is true, then an error and stack trace will be displayed in html or sent via JSON, depending on the client's request. If it is not set, then an unhandled error handler is attached that will send a 500 Internal Server Error in text/plain unless the error itself specifies a different message and/or status code to send.
• bedrock-express.start
  • Emitted before bedrock-express.ready to allow listeners to perform any custom behavior prior to the express server announcing it is ready.
• bedrock-express.ready
  • Emitted after bedrock-express.start, indicating that all listeners should have already completed any special custom behavior on start up.
• bedrock-express.fastify.ready
  • Emitted after bedrock-express.ready once the express app that was assembled via all the previous events has been added to fastify so that it can be served on bedrock-server.ready.

License

Apache License, Version 2.0 Copyright 2011-2024 Digital Bazaar, Inc.

Other Bedrock libraries are available under a non-commercial license for uses such as self-study, research, personal projects, or for evaluation purposes. See the Bedrock Non-Commercial License v1.0 for details.

Commercial licensing and support are available by contacting Digital Bazaar support@digitalbazaar.com.