_base.js

这是一个ajax的例子大家好好的看看就是一个鱼眼的效果

if(!dojo._hasResource["dojox.cometd._base"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
dojo._hasResource["dojox.cometd._base"] = true;
dojo.provide("dojox.cometd._base");
dojo.require("dojo.AdapterRegistry");
dojo.require("dojo.io.script");


/*
 * this file defines Comet protocol client. Actual message transport is
 * deferred to one of several connection type implementations. The default is a
 * long-polling implementation. A single global object named "dojox.cometd" is
 * used to mediate for these connection types in order to provide a stable
 * interface.
 *
 * extensions modules may be loaded (eg "dojox.cometd.timestamp", that use
 * the cometd._extendInList and cometd._extendOutList fields to provide functions
 * that extend and handling incoming and outgoing messages.
 */

dojox.cometd = new function(){
	
	// cometd states:

	// alex; OMG, these "constants" need to die. Java truly is a degenerative disease.
 	this.DISCONNECTED = "DISCONNECTED";		// _initialized==false 	&& _connected==false
 	this.CONNECTING = "CONNECTING";			// _initialized==true	&& _connected==false (handshake sent)
 	this.CONNECTED = "CONNECTED";			// _initialized==true	&& _connected==true (first successful connect)
 	this.DISCONNECTING = "DISCONNECING";	// _initialized==false 	&& _connected==true (disconnect sent)
 	
	this._initialized = false;
	this._connected = false;
	this._polling = false;

	this.expectedNetworkDelay = 5000; // expected max network delay
	this.connectTimeout = 0;    // If set, used as ms to wait for a connect response and sent as the advised timeout

	this.connectionTypes = new dojo.AdapterRegistry(true);

	this.version =	"1.0";
	this.minimumVersion = "0.9";
	this.clientId = null;
	this.messageId = 0;
	this.batch = 0;

	this._isXD = false;
	this.handshakeReturn = null;
	this.currentTransport = null;
	this.url = null;
	this.lastMessage = null;
	this._messageQ = [];
	this.handleAs = "json-comment-optional";
	this._advice = {};
	this._backoffInterval = 0;
	this._backoffIncrement = 1000;
	this._backoffMax = 60000;
	this._deferredSubscribes = {};
	this._deferredUnsubscribes = {};
	this._subscriptions = [];
	this._extendInList = [];	// List of functions invoked before delivering messages
	this._extendOutList = [];	// List of functions invoked before sending messages

	this.state = function() {
		return this._initialized ? 
			(this._connected ? "CONNECTED" : "CONNECTING") : 
			( this._connected ? "DISCONNECTING" : "DISCONNECTED");
	}

	this.init = function(	/*String*/	root,
				/*Object?*/ props,
				/*Object?*/ bargs){	// return: dojo.Deferred
		//	summary:
		//		Initialize the cometd implementation of the Bayeux protocol
		//	description:
		//		Initialize the cometd implementation of the Bayeux protocol by
		//		sending a handshake message. The cometd state will be changed to CONNECTING
		//		until a handshake response is received and the first successful connect message
		//		has returned.
		//		The protocol state changes may be monitored
		//		by subscribing to the dojo topic "/cometd/meta" where events are
		//		published in the form {cometd:this,action:"handshake",successful:true,state:this.state()}
		//	root:
		//		The URL of the cometd server. If the root is absolute, the host
		//		is examined to determine if xd transport is needed. Otherwise the
		//		same domain is assumed.
		//	props:
		//		An optional object that is used as the basis of the handshake message
		//	bargs:
		//		An optional object of bind args mixed in with the send of the handshake
		//	example:
		//	|	dojox.cometd.init("/cometd");
		//	|	dojox.cometd.init("http://xdHost/cometd",{ext:{user:"fred",pwd:"secret"}});


		// FIXME: if the root isn't from the same host, we should automatically
		// try to select an XD-capable transport
		props = props||{};
		// go ask the short bus server what we can support
		props.version = this.version;
		props.minimumVersion = this.minimumVersion;
		props.channel = "/meta/handshake";
		props.id = ""+this.messageId++;

		this.url = root||dojo.config["cometdRoot"];
		if(!this.url){
			console.debug("no cometd root specified in djConfig and no root passed");
			return null;
		}

		// Are we x-domain? borrowed from dojo.uri.Uri in lieu of fixed host and port properties
		var regexp = "^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\\?([^#]*))?(#(.*))?$";
		var parts = (""+window.location).match(new RegExp(regexp));
		if(parts[4]){
			var tmp = parts[4].split(":");
			var thisHost = tmp[0];
			var thisPort = tmp[1]||"80"; // FIXME: match 443

			parts = this.url.match(new RegExp(regexp));
			if(parts[4]){
				tmp = parts[4].split(":");
				var urlHost = tmp[0];
				var urlPort = tmp[1]||"80";
				this._isXD = ((urlHost != thisHost)||(urlPort != thisPort));
			}
		}

		if(!this._isXD){
			if(props.ext){
				if(props.ext["json-comment-filtered"]!==true && props.ext["json-comment-filtered"]!==false){
					props.ext["json-comment-filtered"] = true;
				}
			}else{
				props.ext = { "json-comment-filtered": true };
			}
			props.supportedConnectionTypes = dojo.map(this.connectionTypes.pairs, "return item[0]");
		}

		props = this._extendOut(props);

		var bindArgs = {
			url: this.url,
			handleAs: this.handleAs,
			content: { "message": dojo.toJson([props]) },
			load: dojo.hitch(this,function(msg){
				this._backon();
				this._finishInit(msg);
			}),
			error: dojo.hitch(this,function(e){
				console.debug("handshake error!:",e);
				this._backoff();
				this._finishInit([{}]);
			})
		};

		if(bargs){
			dojo.mixin(bindArgs, bargs);
		}
		this._props = props;
		for(var tname in this._subscriptions){
			for(var sub in this._subscriptions[tname]){
				if(this._subscriptions[tname][sub].topic){
		 			dojo.unsubscribe(this._subscriptions[tname][sub].topic);
				}
			}
		}
		this._messageQ = [];
		this._subscriptions = [];
		this._initialized = true;
		this.batch = 0;
		this.startBatch();
		
		var r;
		// if xdomain, then we assume jsonp for handshake
		if(this._isXD){
			bindArgs.callbackParamName = "jsonp";
			r = dojo.io.script.get(bindArgs);
		}else{
			r = dojo.xhrPost(bindArgs);
		}
		dojo.publish("/cometd/meta", [
			{
				cometd: this,
				action: "handshake",
				successful: true,
				state: this.state()
			}
		]);
		return r;
	}
	
	
	this.publish = function(/*String*/ channel, /*Object*/ data, /*Object?*/ props){
		// summary:
		//		publishes the passed message to the cometd server for delivery
		//		on the specified topic
		// channel:
		//		the destination channel for the message
		// data:
		//		a JSON object containing the message "payload"
		// properties:
		//		Optional. Other meta-data to be mixed into the top-level of the
		//		message
		var message = {
			data: data,
			channel: channel
		};
		if(props){
			dojo.mixin(message, props);
		}
		this._sendMessage(message);
	}

	
	this.subscribe = function(	/*String */	channel,
					/*Object */	objOrFunc,
					/*String */	funcName,
					/*Object?*/ props){ // return: dojo.Deferred
		//	summary:
		//		inform the server of this client's interest in channel
		//	description:
		//		`dojox.cometd.subscribe()` handles all the hard work of telling
		//		the server that we want to be notified when events are
		//		published on a particular topic. `subscribe` accepts a function
		//		to handle messages and returns a `dojo.Deferred` object which
		//		has an extra property added to it which makes it suitable for
		//		passing to `dojox.cometd.unsubscribe()` as a "subscription
		//		handle" (much like the handle object that `dojo.connect()`
		//		produces and which `dojo.disconnect()` expects).
		//		
		//		Note that of a subscription is registered before a connection
		//		with the server is established, events sent before the
		//		connection is established will not be delivered to this client.
		//		The deferred object which `subscribe` returns will callback
		//		when the server successfuly acknolwedges receipt of our
		//		"subscribe" request.
		//	channel:
		//		name of the cometd channel to subscribe to
		//	objOrFunc:
		//		an object scope for funcName or the name or reference to a
		//		function to be called when messages are delivered to the
		//		channel
		//	funcName:
		//		the second half of the objOrFunc/funcName pair for identifying
		//		a callback function to notifiy upon channel message delivery
		//	example:
		//		Simple subscribe use-case
		//	|	dojox.cometd.init("http://myserver.com:8080/cometd");
		//	|	// log out all incoming messages on /foo/bar
		//	|	dojox.cometd.subscribe("/foo/bar", console, "debug");
		//	example:
		//		Subscribe before connection is initialized
		//	|	dojox.cometd.subscribe("/foo/bar", console, "debug");
		//	|	dojox.cometd.init("http://myserver.com:8080/cometd");
		//	example:
		//		Subscribe an unsubscribe
		//	|	dojox.cometd.init("http://myserver.com:8080/cometd");
		//	|	var h = dojox.cometd.subscribe("/foo/bar", console, "debug");
		//	|	dojox.cometd.unsubscribe(h);
		//	example:
		//		Listen for successful subscription:
		//	|	dojox.cometd.init("http://myserver.com:8080/cometd");
		//	|	var h = dojox.cometd.subscribe("/foo/bar", console, "debug");
		//	|	h.addCallback(function(){
		//	|		console.debug("subscription to /foo/bar established");
		//	|	});

		props = props||{};
		if(objOrFunc){
			var tname = "/cometd"+channel;
			var subs = this._subscriptions[tname];
			if(!subs || subs.length==0){
				subs = [];
				props.channel = "/meta/subscribe";
				props.subscription = channel;
				this._sendMessage(props);
				
				var _ds = this._deferredSubscribes;
				if(_ds[channel]){
					_ds[channel].cancel();
					delete _ds[channel];
				}
				_ds[channel] = new dojo.Deferred();
			}
			
			for(var i in subs){
				if( subs[i].objOrFunc === objOrFunc && (!subs[i].funcName&&!funcName||subs[i].funcName==funcName) ){
					return null;
				}
			}
			
			var topic = dojo.subscribe(tname, objOrFunc, funcName);
			subs.push({ 
				topic: topic, 
				objOrFunc: objOrFunc, 
				funcName: funcName
			});
			this._subscriptions[tname] = subs;
		}
		var ret = this._deferredSubscribes[channel]||{};
		ret.args = dojo._toArray(arguments);
		return ret; // dojo.Deferred
	}



	this.unsubscribe = function(	/*String*/	channel,
					/*Object?*/ objOrFunc,
					/*String?*/ funcName,
					/*Object?*/ props){
		// summary:
		//		inform the server of this client's disinterest in channel
		// channel:
		//		name of the cometd channel to unsubscribe from
		// objOrFunc:
		//		an object scope for funcName or the name or reference to a
		//		function to be called when messages are delivered to the
		//		channel. If null then all subscribers to the channel are unsubscribed.
		// funcName:
		//		the second half of the objOrFunc/funcName pair for identifying
		//		a callback function to notifiy upon channel message delivery

		if(
			(arguments.length == 1) &&
			(!dojo.isString(channel)) &&
			(channel.args)
		){
			// it's a subscription handle, unroll
			return this.unsubscribe.apply(this, channel.args);
		}
		
		var tname = "/cometd"+channel;
		var subs = this._subscriptions[tname];
		if(!subs || subs.length==0){
			return null;
		}

		var s=0;
		for(var i in subs){
			var sb = subs[i];
			if( (!objOrFunc) ||
				(
					sb.objOrFunc===objOrFunc &&
					(!sb.funcName && !funcName || sb.funcName==funcName)
				)
			){
				dojo.unsubscribe(subs[i].topic);
				delete subs[i];
			}else{
				s++;
			}
		}
		
		if(s==0){
			props = props||{};
			props.channel = "/meta/unsubscribe";
			props.subscription = channel;
			delete this._subscriptions[tname];
			this._sendMessage(props);
			this._deferredUnsubscribes[channel] = new dojo.Deferred();
			if (this._deferredSubscribes[channel]){
				this._deferredSubscribes[channel].cancel();
				delete this._deferredSubscribes[channel];
			}
		}
		return this._deferredUnsubscribes[channel]; // dojo.Deferred
	}
	
	
	this.disconnect = function(){
		//	summary:
		//		Disconnect from the server.
		//	description:
		//		Disconnect from the server by sending a disconnect message
		//	example:
		//	|	dojox.cometd.disconnect();

		for(var tname in this._subscriptions){
			for(var sub in this._subscriptions[tname]){
				if(this._subscriptions[tname][sub].topic){
					dojo.unsubscribe(this._subscriptions[tname][sub].topic);
				}
			}
		}
		this._subscriptions = [];
		this._messageQ = [];
		if(this._initialized && this.currentTransport){
			this._initialized=false;
			this.currentTransport.disconnect();
		}
		if(!this._polling) {
			this._connected=false;
			dojo.publish("/cometd/meta", [{cometd:this,action:"connect",successful:false,state:this.state()}]);
		}
		this._initialized=false;
		dojo.publish("/cometd/meta", [{cometd:this,action:"disconnect",successful:true,state:this.state()}]);
	}

	
	// public extension points
	
	this.subscribed = function(	/*String*/channel, /*Object*/message){ }

	this.unsubscribed = function(/*String*/channel, /*Object*/message){ }


	// private methods (TODO name all with leading _)

	this.tunnelInit = function(childLocation, childDomain){
		// placeholder - replaced by _finishInit
	}
	
	this.tunnelCollapse = function(){
		// placeholder - replaced by _finishInit
	}
	
	this._backoff = function(){
		if(!this._advice){
			this._advice={reconnect:"retry",interval:0};
		}
		else if(!this._advice.interval){
			this._advice.interval=0;
		}
		if(this._backoffInterval<this._backoffMax){
			this._backoffInterval+=this._backoffIncrement;
		}
	}
	
	this._backon = function(){
		this._backoffInterval=0;
	}

	this._interval = function(){
		var i=this._backoffInterval+(this._advice?(this._advice.interval?this._advice.interval:0):0);
		if (i>0)
			console.debug("Retry in interval+backoff="+this._advice.interval+"+"+this._backoffInterval+"="+i+"ms");
		return i;
	}

	this._finishInit = function(data){
		//	summary:
		//		Handle the handshake return from the server and initialize
		//		connection if all is OK
		data = data[0];
		this.handshakeReturn = data;
		
		// remember any advice
		if(data["advice"]){
			this._advice = data.advice;
		}

		var successful=data.successful?data.successful:false;
		
		// check version
		if(data.version < this.minimumVersion){
			console.debug("cometd protocol version mismatch. We wanted", this.minimumVersion, "but got", data.version);
			successful=false;
			this._advice.reconnect="none";
		}
		
		// If all OK
		if(successful){
			// pick a transport
			this.currentTransport = this.connectionTypes.match(
				data.supportedConnectionTypes,
				data.version,
				this._isXD
			);
			// initialize the transport
			this.currentTransport._cometd = this;
			this.currentTransport.version = data.version;
			this.clientId = data.clientId;
			this.tunnelInit = dojo.hitch(this.currentTransport, "tunnelInit");
			this.tunnelCollapse = dojo.hitch(this.currentTransport, "tunnelCollapse");
			this.currentTransport.startup(data);
		}

		dojo.publish("/cometd/meta", [{cometd:this,action:"handshook",successful:successful,state:this.state()}]);