connect

High performance middleware framework

Connect

Connect is an extensible HTTP server framework for node using "plugins" known as middleware.

var connect = require('connect');
var http = require('http');
 
var app = connect();
 
// gzip/deflate outgoing responses 
var compression = require('compression');
app.use(compression());
 
// store session state in browser cookie 
var cookieSession = require('cookie-session');
app.use(cookieSession({
    keys: ['secret1', 'secret2']
}));
 
// parse urlencoded request bodies into req.body 
var bodyParser = require('body-parser');
app.use(bodyParser.urlencoded());
 
// respond to all requests 
app.use(function(req, res){
  res.end('Hello from Connect!\n');
});
 
//create node.js http server and listen on port 
http.createServer(app).listen(3000);

Getting Started

Connect is a simple framework to glue together various "middleware" to handle requests.

Install Connect

$ npm install connect

Create an app

The main component is a Connect "app". This will store all the middleware added and is, itself, a function.

var app = connect();

Use middleware

The core of Connect is "using" middleware. Middleware are added as a "stack" where incoming requests will execute each middleware one-by-one until a middleware does not call next() within it.

app.use(function middleware1(req, res, next) {
  // middleware 1 
  next();
});
app.use(function middleware2(req, res, next) {
  // middleware 2 
  next();
});

Mount middleware

The .use() method also takes an optional path string that is matched against the beginning of the incoming request URL. This allows for basic routing.

app.use('/foo', function fooMiddleware(req, res, next) {
  // req.url starts with "/foo" 
  next();
});
app.use('/bar', function barMiddleware(req, res, next) {
  // req.url starts with "/bar" 
  next();
});

There are special cases of "error-handling" middleware. There are middleware where the function takes exactly 4 arguments. When a middleware passes an error to next, the app will proceed to look for the error middleware that was declared after that middleware and invoke it, skipping any error middleware above that middleware and any non-error middleware below.

// regular middleware 
app.use(function (req, res, next) {
  // i had an error 
  next(new Error('boom!'));
});
 
// error middleware for errors that occurred in middleware 
// declared before this 
app.use(function onerror(err, req, res, next) {
  // an error occurred! 
});

Create a server from the app

The last step is to actually use the Connect app in a server. The .listen() method is a convenience to start a HTTP server.

var server = app.listen(port);

The app itself is really just a function with three arguments, so it can also be handed to .createServer() in Node.js.

var server = http.createServer(app);

Middleware

These middleware and libraries are officially supported by the Connect/Express team:

body-parser - previous bodyParser, json, and urlencoded. You may also be interested in:
- body
- co-body
- raw-body
compression - previously compress
connect-timeout - previously timeout
cookie-parser - previously cookieParser
cookie-session - previously cookieSession
csurf - previously csrf
errorhandler - previously error-handler
express-session - previously session
method-override - previously method-override
morgan - previously logger
response-time - previously response-time
serve-favicon - previously favicon
serve-index - previously directory
serve-static - previously static
vhost - previously vhost

Most of these are exact ports of their Connect 2.x equivalents. The primary exception is cookie-session.

Some middleware previously included with Connect are no longer supported by the Connect/Express team, are replaced by an alternative module, or should be superseded by a better module. Use one of these alternatives instead: