Express4x Learn
1、basic
var express = require('../../lib/express');
var app = express();
// fake a database
var users = [
{ id: 0, name: 'tj', email: 'tj@vision-media.ca', role: 'member' }
, { id: 1, name: 'ciaran', email: 'ciaranj@gmail.com', role: 'member' }
];
// middleware
function loadUser(req, res, next) {
// app.get("/xxx/:id") ==> req.params.id
var user = users[req.params.id];
if (user) {
req.user = user; // 消息传递机制
next();
} else { // 错误处理机制，服务器会统一处理 error
next(new Error('Failed to load user ' + req.params.id));
}
}
// add middleware, processed by express in order
app.use(function(req, res, next){
req.authenticatedUser = users[0];
next();
});
app.get('/', function(req, res){
res.redirect('/user/0');
});
app.get('/user/:id', loadUser, function(req, res){
res.send('Viewing user ' + req.user.name);
});
app.listen(3000);
2、error-handling
// nearly last middleware to use, to handle invalid url path;
app.use(function(req, res, next){
res.status(404);
res.render('404', { url: req.url });
});
// when connect has an error, it will invoke ONLY error-handling middleware.
// If we were to next() here, any remaining non-error-handling middleware would then be executed,
// or if we next(err), only error-handling middleware would be executed.
app.use(function(err, req, res, next){
res.status(err.status || 500);
res.render('500', { error: err });
});
3、mount middleware with prefixPath
var apiKeys = ['foo', 'bar', 'baz'];
function createError(status, msg) {
var err = new Error(msg);
err.status = status;
return err;
}
/**
* by mounting this middleware to "/api" prefixPath
* meaning only req.url's paths prefixed with "/api" will cause this middleware to be invoked
* at which point req.url is stripped when the function is invoked.
* This affects this middleware only, subsequent middleware will see req.url as not modefied
* unless it's mounted also.
*/
app.use('/api', function(req, res, next){
var key = req.query['api-key'];
if (!key) return next(createError(400, 'api key required'));
if (apiKeys.indexOf(key) === -1) return next(createError(401, 'invalid api key'));
req.key = key;
next();
});
4、Cookies and Session
// parses request cookies, populating `req.cookies` and `req.signedCookies`
// when the secret key is passed, used for signing the cookies.
// signature algorithm and secret key must only be knowned by server.
app.use(cookieParser('my secret key here'));
// Populates req.session, recognize user by signedSessionCookie.
app.use(session());
5、app.param
For example when :user is present in a route path, you may map user loading logic to automatically provide req.user to the route, or perform validations on the parameter input.
// for example: /user/:user
app.param('user', function(req, res, next, userId){
if (req.user = users[userId]) {
next();
} else {
next(new Error('failed to find user'));
}
});
It is important to realize that any route that triggered a named parameter function to run will only be run if next was not called with an error in the named parameter handler.
6、content-negotiation
res.format(object)
Performs content-negotiation on the request Accept header field when present. When Accept is not present, the first callback is invoked, otherwise the first match is used. When no match is performed the server responds with 406 “Not Acceptable”. if object.default is defined as a function, then it will be invoked instead of a response of 406.
Use MIME
res.format({
'text/html': function(){
res.send('hey');
},
'application/json': function(){
res.send({ message: 'hey' });
}
});
OR ExtName
res.format({
html: function(){
res.send('hey');
},
json: function(){
res.send({ message: 'hey' });
}
});
7、vhost
/*
edit /etc/hosts:
127.0.0.1 foo.example.com
127.0.0.1 bar.example.com
127.0.0.1 example.com
*/
var main = express();
main.get('/', function(req, res){
res.send('Hello from main app!');
});
main.get('/:sub', function(req, res){
res.send('requested ' + req.params.sub);
});
// Redirect app
var redirect = express();
redirect.all('*', function(req, res){
res.redirect('http://example.com:3000/' + req.subdomains[0]);
});
// Vhost app
var app = express();
app.use(vhost('*.example.com', redirect)); // Serves all subdomains via Redirect app
app.use(vhost('example.com', main)); // Serves top level domain via Main server app
app.listen(3000);
8、single MVC
module.exports = function (parent, options) {
var verbose = options.verbose;
fs.readdirSync(__dirname + '/../controllers').forEach(function (name) {
var obj = require('./../controllers/' + name);
var name = obj.name || name;
var prefix = obj.prefix || '';
var app = express();
var method;
var path;
app.set('views', __dirname + '/../controllers/' + name + '/views');
// before middleware support
if (obj.before) {
path = '/' + name + '/:' + name + '_id';
app.all(path, obj.before);
path = '/' + name + '/:' + name + '_id/*';
app.all(path, obj.before);
}
for (var key in obj) {
// "reserved" exports for other reasons
if (~['name', 'prefix', 'engine', 'before'].indexOf(key)) continue;
switch (key) {
case 'show':
method = 'get';
path = '/' + name + '/:' + name + '_id';
break;
case 'list':
method = 'get';
path = '/' + name + 's';
break;
case 'edit':
method = 'get';
path = '/' + name + '/:' + name + '_id/edit';
break;
case 'update':
method = 'put';
path = '/' + name + '/:' + name + '_id';
break;
case 'create':
method = 'post';
path = '/' + name;
break;
default:
throw new Error('unrecognized route: ' + name + '.' + key);
}
path = prefix + path;
app[method](path, obj[key]);
}
// mount the app
parent.use(app);
});
};