- Author:
- David Nickerson <nickerso@users.sourceforge.net>
- Date:
- 2009-07-16 02:00:03+12:00
- Desc:
- the starting point for the HH tutorial example
- Permanent Source URI:
- https://models.fieldml.org/workspace/a1/rawfile/f6a8f90307388eb4b040ee3566b84d88b59247f7/dojo-presentation/js/dojo/dojox/cometd/HttpChannels.js
dojo.provide("dojox.cometd.HttpChannels");
dojo.require("dojox.rpc.Client");
dojo.require("dojox.io.httpParse");
if(dojox.data && dojox.data.JsonRestStore){
dojo.require("dojox.data.restListener");
}
// Note that cometd _base is _not_ required, this can run standalone, but ifyou want
// cometd functionality, you must explicitly load/require it elsewhere, and cometd._base
// MUST be loaded prior to HttpChannels ifyou use it.
// summary:
// HTTP Channels - An HTTP Based approach to Comet transport with full HTTP messaging
// semantics including REST
// HTTP Channels is a efficient, reliable duplex transport for Comet
// description:
// This can be used:
// 1. As a cometd transport
// 2. As an enhancement for the REST RPC service, to enable "live" data (real-time updates directly alter the data in indexes)
// 2a. With the JsonRestStore (which is driven by the REST RPC service), so this dojo.data has real-time data. Updates can be heard through the dojo.data notification API.
// 3. As a standalone transport. To use it as a standalone transport looks like this:
// | dojox.cometd.HttpChannels.open();
// | dojox.cometd.HttpChannels.get("/myResource",{callback:function(){
// | // this is called when the resource is first retrieved and any time the
// | // resource is changed in the future. This provides a means for retrieving a
// | // resource and subscribing to it in a single request
// | });
// | dojox.cometd.HttpChannels.subscribe("/anotherResource",{callback:function(){
// | // this is called when the resource is changed in the future
// | });
// Channels HTTP can be configured to a different delays:
// | dojox.cometd.HttpChannels.autoReconnectTime = 60000; // reconnect after one minute
//
(function(){
dojo.declare("dojox.cometd.HttpChannels", null, {
constructor: function(options){
// summary:
// Initiates the HTTP Channels protocol
// options:
// Keyword arguments:
// The *autoSubscribeRoot* parameter:
// When this is set, all REST service requests that have this
// prefix will be auto-subscribed. The default is '/' (all REST requests).
// The *url* parameter:
// This is the url to connect to for server-sent messages. The default
// is "/channels".
// The *autoReconnectTime* parameter:
// This is amount time to wait to reconnect with a connection is broken
dojo.mixin(this,options);
// If we have a Rest service available and we are auto subscribing, we will augment the Rest service
if(dojox.rpc.Rest && this.autoSubscribeRoot){
// override the default Rest handler so we can add subscription requests
var defaultGet = dojox.rpc.Rest._get;
var self = this;
dojox.rpc.Rest._get = function(service, id){
// when there is a REST get, we will intercept and add our own xhr handler
var defaultXhrGet = dojo.xhrGet;
dojo.xhrGet = function(r){
var autoSubscribeRoot = self.autoSubscribeRoot;
return (autoSubscribeRoot && r.url.substring(0, autoSubscribeRoot.length) == autoSubscribeRoot) ?
self.get(r.url,r) : // auto-subscribe
defaultXhrGet(r); // plain XHR request
};
var result = defaultGet.apply(this,arguments);
dojo.xhrGet = defaultXhrGet;
return result;
};
}
if(dojox.data && dojox.data.restListener){
this.receive = dojox.data.restListener;
}
},
absoluteUrl: function(baseUrl,relativeUrl){
return new dojo._Url(baseUrl,relativeUrl)+'';
},
acceptType: "x-application/http+json,application/http;q=0.9,*/*;q=0.7",
subscriptions: {},
subCallbacks: {},
autoReconnectTime: 30000,
sendAsJson: false,
url: '/channels',
autoSubscribeRoot: '/',
open: function(){
// summary:
// Startup the transport (connect to the "channels" resource to receive updates from the server).
//
// description:
// Note that if there is no connection open, this is automatically called when you do a subscription,
// it is often not necessary to call this
//
if(!this.connected){
this.connectionId = dojox._clientId;
var clientIdHeader = this.started ? 'X-Client-Id' : 'X-Create-Client-Id';
var headers = {Accept:this.acceptType};
headers[clientIdHeader] = this.connectionId;
var dfd = dojo.xhrPost({headers:headers, url: this.url, noStatus: true});
var self = this;
this.lastIndex = 0;
var onerror, onprogress = function(data){ // get all the possible event handlers
if(typeof dojo == 'undefined'){
return null;// this can be called after dojo is unloaded, just do nothing in that case
}
data = data.substring(self.lastIndex);
var contentType = xhr && (xhr.contentType || xhr.getResponseHeader("Content-Type"));
self.started = true;
var error = self.onprogress(xhr,data,contentType);
if(error){
onerror();
return new Error(error);
}
if(!xhr || xhr.readyState==4){
xhr = null;
if(self.connected){
self.connected = false;
self.open();
}
}
return data;
};
onerror = function(error){
if(self.started){ // this means we need to reconnect
self.started = false;
self.connected = false;
var subscriptions = self.subscriptions;
self.subscriptions = {};
for(var i in subscriptions){
self.subscribe(i,{since:subscriptions[i]});
}
}else{
self.disconnected();
}
return error;
};
dfd.addCallbacks(onprogress,onerror);
var xhr = dfd.ioArgs.xhr; // this may not exist if we are not using XHR, but an alternate XHR plugin
if(xhr){
// if we are doing a monitorable XHR, we want to listen to streaming events
xhr.onreadystatechange = function(){
var responseText;
try{
if(xhr.readyState == 3){// only for progress, the deferred object will handle the finished responses
self.readyState = 3;
responseText = xhr.responseText;
}
} catch(e){
}
if(typeof data=='string'){
onprogress(responseText);
}
}
}
if(window.attachEvent){// IE needs a little help with cleanup
attachEvent("onunload",function(){
self.connected= false;
if(xhr){
xhr.abort();
}
});
}
this.connected = true;
}
},
_send: function(method,args,data){
// fire an XHR with appropriate modification for JSON handling
if(this.sendAsJson){
// send use JSON Messaging
args.postBody = dojo.toJson({
target:args.url,
method:method,
content: data,
params:args.content,
subscribe:headers["X-Subscribe"]
});
args.url = this.url;
method = "POST";
}else{
args.postData = dojo.toJson(data);
}
return dojo.xhr(method,args,args.postBody);
},
subscribe: function(/*String*/channel, /*dojo.__XhrArgs?*/args){
// summary:
// Subscribes to a channel/uri, and returns a dojo.Deferred object for the response from
// the subscription request
//
// channel:
// the uri for the resource you want to monitor
//
// args:
// See dojo.xhr
//
// headers:
// These are the headers to be applied to the channel subscription request
//
// callback:
// This will be called when a event occurs for the channel
// The callback will be called with a single argument:
// | callback(message)
// where message is an object that follows the XHR API:
// status : Http status
// statusText : Http status text
// getAllResponseHeaders() : The response headers
// getResponseHeaders(headerName) : Retrieve a header by name
// responseText : The response body as text
// with the following additional Bayeux properties
// data : The response body as JSON
// channel : The channel/url of the response
args = args || {};
args.url = this.absoluteUrl(this.url, channel);
if(args.headers){
// FIXME: combining Ranges with notifications is very complicated, we will save that for a future version
delete args.headers.Range;
}
var oldSince = this.subscriptions[channel];
var method = args.method || "HEAD"; // HEAD is the default for a subscription
var since = args.since;
var callback = args.callback;
var headers = args.headers || (args.headers = {});
this.subscriptions[channel] = since || oldSince || 0;
var oldCallback = this.subCallbacks[channel];
if(callback){
this.subCallbacks[channel] = oldCallback ? function(m){
oldCallback(m);
callback(m);
} : callback;
}
if(!this.connected){
this.open();
}
if(oldSince === undefined || oldSince != since){
headers["Cache-Control"] = "max-age=0";
since = typeof since == 'number' ? new Date(since).toUTCString() : since;
if(since){
headers["X-Subscribe-Since"] = since;
}
headers["X-Subscribe"] = args.unsubscribe ? 'none' : '*';
var dfd = this._send(method,args);
var self = this;
dfd.addBoth(function(result){
var xhr = dfd.ioArgs.xhr;
if(!(result instanceof Error)){
if(args.confirmation){
args.confirmation();
}
}
if(xhr && xhr.getResponseHeader("X-Subscribed") == "OK"){
var lastMod = xhr.getResponseHeader('Last-Modified');
if(xhr.responseText){
self.subscriptions[channel] = lastMod || new Date().toUTCString();
}else{
return null; // don't process the response, the response will be received in the main channels response
}
}else if(xhr){ // ifit is not a 202 response, that means it is did not accept the subscription
delete self.subscriptions[channel];
}
if(!(result instanceof Error)){
var message = {
responseText:xhr && xhr.responseText,
channel:channel,
getResponseHeader:function(name){
return xhr.getResponseHeader(name);
},
getAllResponseHeaders:function(){
return xhr.getAllResponseHeaders();
}
};
try{
message.data = result;
}
catch (e){}
if(self.subCallbacks[channel]){
self.subCallbacks[channel](message); // call with the fake xhr object
}
}else{
if(self.subCallbacks[channel]){
self.subCallbacks[channel](xhr); // call with the actual xhr object
}
}
return result;
});
return dfd;
}
return null;
},
publish: function(channel,data){
// summary:
// Publish an event.
// description:
// This does a simple POST operation to the provided URL,
// POST is the semantic equivalent of publishing a message within REST/Channels
// channel:
// Channel/resource path to publish to
// data:
// data to publish
return this._send("POST",{url:channel,contentType : 'application/json'},data);
},
_processMessage: function(message){
message.event = message.event || message.getResponseHeader('X-Event');
if(message.event=="connection-conflict"){
return "conflict"; // indicate an error
}
try{
message.data = message.content || dojo.fromJson(message.responseText);
}
catch(e){}
var self = this;
var loc = message.channel = new dojo._Url(this.url, message.target || message.getResponseHeader('Content-Location'))+'';//for cometd
if(loc in this.subscriptions){
this.subscriptions[loc] = message.getResponseHeader('Last-Modified');
}
if(this.subCallbacks[loc]){
setTimeout(function(){ //give it it's own stack
self.subCallbacks[loc](message);
},0);
}
this.receive(message);
return null;
},
onprogress: function(xhr,data,contentType){
// internal XHR progress handler
if(!contentType || contentType.match(/application\/http\+json/)){
var size = data.length;
data = data.replace(/^\s*[,\[]?/,'['). // must start with a opening bracket
replace(/[,\]]?\s*$/,']'); // and end with a closing bracket
try{
// if this fails, it probably means we have an incomplete JSON object
var xhrs = dojo.fromJson(data);
this.lastIndex += size;
}
catch(e){
}
}
else if(contentType.match(/application\/http/)){
// do HTTP tunnel parsing
var topHeaders = '';
if(xhr && xhr.getAllResponseHeaders){
// mixin/inherit headers from the container response
topHeaders = xhr.getAllResponseHeaders();
}
xhrs = dojox.io.httpParse(data,topHeaders,xhr.readyState != 4);
}
if(xhrs){
for(var i = 0;i < xhrs.length;i++){
if(this._processMessage(xhrs[i])){
return "conflict";
}
}
return null;
}
if(!xhr){
//no streaming and we didn't get any message, must be an error
return "error";
}
if(xhr.readyState != 4){ // we only want finished responses here if we are not streaming
return null;
}
if(xhr.__proto__){// firefox uses this property, so we create an instance to shadow this property
xhr = {channel:"channel",__proto__:xhr};
}
return this._processMessage(xhr);
},
get: function(/*String*/channel, /*dojo.__XhrArgs?*/args){
// summary:
// GET the initial value of the resource and subscribe to it
// See subscribe for parameter values
(args = args || {}).method = "GET";
return this.subscribe(channel,args);
},
receive: function(message){
// summary:
// Called when a message is received from the server
// message:
// A cometd/XHR message
},
disconnected: function(){
// summary:
// called when our channel gets disconnected
var self = this;
if(this.connected){ // ifwe are connected, we shall tryto reconnect
setTimeout(function(){ // auto reconnect
self.open();
},this.autoReconnectTime);
}
this.connected = false;
},
unsubscribe: function(/*String*/channel, /*dojo.__XhrArgs?*/args){
// summary:
// unsubscribes from the resource
// See subscribe for parameter values
args = args || {};
args.unsubscribe = true;
this.subscribe(channel,args); // change the time frame to after 5000AD
},
disconnect: function(){
// summary:
// disconnect from the server
this.connected = false;
this.xhr.abort();
}
});
var Channels = dojox.cometd.HttpChannels.defaultInstance = new dojox.cometd.HttpChannels();
if(dojox.cometd.connectionTypes){
// register as a dojox.cometd transport and wire everything for cometd handling
// below are the necessary adaptions for cometd
Channels.startup = function(data){ // must be able to handle objects or strings
Channels.open();
this._cometd._deliver({channel:"/meta/connect",successful:true}); // tell cometd we are connected so it can proceed to send subscriptions, even though we aren't yet
};
Channels.check = function(types, version, xdomain){
for(var i = 0; i< types.length; i++){
if(types[i] == "http-channels"){
return !xdomain;
}
}
return false;
};
Channels.deliver = function(message){
// nothing to do
};
dojo.connect(this,"receive",null,function(message){
this._cometd._deliver(message);
});
Channels.sendMessages = function(messages){
for(var i = 0; i < messages.length; i++){
var message = messages[i];
var channel = message.channel;
var cometd = this._cometd;
var args = {
confirmation: function(){ // send a confirmation back to cometd
cometd._deliver({channel:channel,successful:true});
}
};
if(channel == '/meta/subscribe'){
this.subscribe(message.subscription,args);
}else if(channel == '/meta/unsubscribe'){
this.unsubscribe(message.subscription,args);
}else if(channel == '/meta/connect'){
args.confirmation();
}else if(channel == '/meta/disconnect'){
Channels.disconnect();
args.confirmation();
}else if(channel.substring(0,6) != '/meta/'){
this.publish(channel,message.data);
}
}
};
dojox.cometd.connectionTypes.register("http-channels", Channels.check, Channels,false,true);
}
})();
