koa-lite/lib/application.js

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/**
* Module dependencies.
*/
var debug = require('debug')('koa:application');
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var Emitter = require('events').EventEmitter;
var compose = require('koa-compose');
var context = require('./context');
var Cookies = require('cookies');
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var Stream = require('stream');
var http = require('http');
var co = require('co');
/**
* Application prototype.
*/
var app = Application.prototype;
/**
* Expose `Application`.
*/
exports = module.exports = Application;
/**
* Initialize a new `Application`.
*
* @api public
*/
function Application() {
if (!(this instanceof Application)) return new Application;
this.env = process.env.NODE_ENV || 'development';
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this.on('error', this.onerror);
this.outputErrors = 'test' != this.env;
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this.subdomainOffset = 2;
this.poweredBy = true;
this.jsonSpaces = 2;
this.middleware = [];
this.Context = createContext();
this.context(context);
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}
/**
* Inherit from `Emitter.prototype`.
*/
Application.prototype.__proto__ = Emitter.prototype;
/**
* Shorthand for:
*
* http.createServer(app.callback()).listen(...)
*
* @param {Mixed} ...
* @return {Server}
* @api public
*/
app.listen = function(){
var server = http.createServer(this.callback());
return server.listen.apply(server, arguments);
};
/**
* Use the given middleware `fn`.
*
* @param {Function} fn
* @return {Application} self
* @api public
*/
app.use = function(fn){
debug('use %s', fn.name || '-');
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this.middleware.push(fn);
return this;
};
/**
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* Mixin `obj` to this app's context.
*
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* app.context({
* get something(){
* return 'hi';
* },
*
* set something(val){
* this._something = val;
* },
*
* render: function(){
* this.body = '<html></html>';
* }
* });
*
* @param {Object} obj
* @return {Application} self
* @api public
*/
app.context = function(obj){
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var ctx = this.Context.prototype;
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var names = Object.getOwnPropertyNames(obj);
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debug('context: %j', names);
names.forEach(function(name){
if (Object.getOwnPropertyDescriptor(ctx, name)) {
debug('context: overwriting %j', name);
}
var descriptor = Object.getOwnPropertyDescriptor(obj, name);
Object.defineProperty(ctx, name, descriptor);
});
return this;
};
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/**
* Return a request handler callback
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* for node's native http server.
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*
* @return {Function}
* @api public
*/
app.callback = function(){
var mw = [respond].concat(this.middleware);
var gen = compose(mw);
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var self = this;
return function(req, res){
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var ctx = new self.Context(self, req, res);
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co.call(ctx, gen)(function(err){
if (err) ctx.onerror(err);
});
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}
};
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/**
* Default error handler.
*
* @param {Error} err
* @api private
*/
app.onerror = function(err){
if (!this.outputErrors) return;
if (404 == err.status) return;
console.error(err.stack);
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};
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/**
* Response middleware.
*/
function *respond(next){
this.status = 200;
if (this.app.poweredBy) this.set('X-Powered-By', 'koa');
yield next;
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var app = this.app;
var res = this.res;
var body = this.body;
var head = 'HEAD' == this.method;
var noContent = 204 == this.status || 304 == this.status;
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// 404
if (null == body && 200 == this.status) {
this.status = 404;
}
// ignore body
if (noContent) return res.end();
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// status body
if (null == body) {
this.type = 'text';
body = http.STATUS_CODES[this.status];
}
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// Buffer body
if (Buffer.isBuffer(body)) {
if (head) return res.end();
return res.end(body);
}
// string body
if ('string' == typeof body) {
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if (head) return res.end();
return res.end(body);
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}
// Stream body
if (body instanceof Stream) {
if (!~body.listeners('error').indexOf(this.onerror)) body.on('error', this.onerror);
if (head) return res.end();
return body.pipe(res);
}
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// body: json
body = JSON.stringify(body, null, this.app.jsonSpaces);
this.length = Buffer.byteLength(body);
if (head) return res.end();
res.end(body);
}
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/**
* Create a new `Context` constructor.
*
* @return {Function}
* @api private
*/
function createContext() {
return function Context(app, req, res){
this.app = app;
this.req = req;
this.res = res;
this.cookies = new Cookies(req, res);
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this.onerror = this.onerror.bind(this);
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}
}