The source code

###

    (function(){
        var BEFOREREQUEST = "beforerequest",
            REQUESTCOMPLETE = "requestcomplete",
            REQUESTEXCEPTION = "requestexception",
            UNDEFINED = undefined,
            LOAD = 'load',
            POST = 'POST',
            GET = 'GET',
            WINDOW = window;

        /**
         * @class Ext.data.Connection
         * @extends Ext.util.Observable
         * The class encapsulates a connection to the page's originating domain, allowing requests to be made
         * either to a configured URL, or to a URL specified at request time.
         * Requests made by this class are asynchronous, and will return immediately. No data from
         * the server will be available to the statement immediately following the {@link #request} call.
         * To process returned data, use a
         * success callback
         * in the request options object,
         * or an {@link #requestcomplete event listener}.
         * File UploadsFile uploads are not performed using normal "Ajax" techniques, that
         * is they are not performed using XMLHttpRequests. Instead the form is submitted in the standard
         * manner with the DOM <form> element temporarily modified to have its
         * target set to refer
         * to a dynamically generated, hidden <iframe> which is inserted into the document
         * but removed after the return data has been gathered.
         * The server response is parsed by the browser to create the document for the IFRAME. If the
         * server is using JSON to send the return object, then the
         * Content-Type header
         * must be set to "text/html" in order to tell the browser to insert the text unchanged into the document body.
         * Characters which are significant to an HTML parser must be sent as HTML entities, so encode
         * "<" as "&lt;", "&" as "&amp;" etc.
         * The response text is retrieved from the document, and a fake XMLHttpRequest object
         * is created containing a responseText property in order to conform to the
         * requirements of event handlers and callbacks.
         * Be aware that file upload packets are sent with the content type multipart/form
         * and some server technologies (notably JEE) may require some custom processing in order to
         * retrieve parameter names and parameter values from the packet content.
         * @constructor
         * @param {Object} config a configuration object.
         */
        Ext.data.Connection = function(config){
            Ext.apply(this, config);
            this.addEvents(
                /**
                 * @event beforerequest
                 * Fires before a network request is made to retrieve a data object.
                 * @param {Connection} conn This Connection object.
                 * @param {Object} options The options config object passed to the {@link #request} method.
                 */
                BEFOREREQUEST,
                /**
                 * @event requestcomplete
                 * Fires if the request was successfully completed.
                 * @param {Connection} conn This Connection object.
                 * @param {Object} response The XHR object containing the response data.
                 * See The XMLHttpRequest Object
                 * for details.
                 * @param {Object} options The options config object passed to the {@link #request} method.
                 */
                REQUESTCOMPLETE,
                /**
                 * @event requestexception
                 * Fires if an error HTTP status was returned from the server.
                 * See HTTP Status Code Definitions
                 * for details of HTTP status codes.
                 * @param {Connection} conn This Connection object.
                 * @param {Object} response The XHR object containing the response data.
                 * See The XMLHttpRequest Object
                 * for details.
                 * @param {Object} options The options config object passed to the {@link #request} method.
                 */
                REQUESTEXCEPTION
            );
            Ext.data.Connection.superclass.constructor.call(this);
        };

        // private
        function handleResponse(response){
            this.transId = false;
            var options = response.argument.options;
            response.argument = options ? options.argument : null;
            this.fireEvent(REQUESTCOMPLETE, this, response, options);
            if(options.success){
                options.success.call(options.scope, response, options);
            }
            if(options.callback){
                options.callback.call(options.scope, options, true, response);
            }
        }

        // private
        function handleFailure(response, e){
            this.transId = false;
            var options = response.argument.options;
            response.argument = options ? options.argument : null;
            this.fireEvent(REQUESTEXCEPTION, this, response, options, e);
            if(options.failure){
                options.failure.call(options.scope, response, options);
            }
            if(options.callback){
                options.callback.call(options.scope, options, false, response);
            }
        }

        // private
        function doFormUpload(o, ps, url){
            var id = Ext.id(),
                doc = document,
                frame = doc.createElement('iframe'),
                form = Ext.getDom(o.form),
                hiddens = [],
                hd,
                encoding = 'multipart/form-data',
                buf = {
                    target: form.target,
                    method: form.method,
                    encoding: form.encoding,
                    enctype: form.enctype,
                    action: form.action
                };

            Ext.apply(frame, {
                id: id,
                name: id,
                className: 'x-hidden',
                src: Ext.SSL_SECURE_URL // for IE
            });
            doc.body.appendChild(frame);

            // This is required so that IE doesn't pop the response up in a new window.
            if(Ext.isIE){
               document.frames[id].name = id;
            }

            Ext.apply(form, {
                target: id,
                method: POST,
                enctype: encoding,
                encoding: encoding,
                action: url || buf.action
            });

            // add dynamic params
            ps = Ext.urlDecode(ps, false);
            for(var k in ps){
                if(ps.hasOwnProperty(k)){
                    hd = doc.createElement('input');
                    hd.type = 'hidden';
                    hd.value = ps[hd.name = k];
                    form.appendChild(hd);
                    hiddens.push(hd);
                }
            }

            function cb(){
                var me = this,
                    // bogus response object
                    r = {responseText : '',
                         responseXML : null,
                         argument : o.argument},
                    doc,
                    firstChild;

                try{
                    doc = frame.contentWindow.document || frame.contentDocument || WINDOW.frames[id].document;
                    if(doc){
                        if(doc.body){
                            if(/textarea/i.test((firstChild = doc.body.firstChild || {}).tagName)){ // json response wrapped in textarea
                                r.responseText = firstChild.value;
                            }else{
                                r.responseText = doc.body.innerHTML;
                            }
                        }
                        //in IE the document may still have a body even if returns XML.
                        r.responseXML = doc.XMLDocument || doc;
                    }
                }
                catch(e) {}

                Ext.EventManager.removeListener(frame, LOAD, cb, me);

                me.fireEvent(REQUESTCOMPLETE, me, r, o);

                function runCallback(fn, scope, args){
                    if(Ext.isFunction(fn)){
                        fn.apply(scope, args);
                    }
                }

                runCallback(o.success, o.scope, [r, o]);
                runCallback(o.callback, o.scope, [o, true, r]);

                if(!me.debugUploads){
                    setTimeout(function(){Ext.removeNode(frame);}, 100);
                }
            }

            Ext.EventManager.on(frame, LOAD, cb, this);
            form.submit();

            Ext.apply(form, buf);
            Ext.each(hiddens, function(h) {
                Ext.removeNode(h);
            });
        }

        Ext.extend(Ext.data.Connection, Ext.util.Observable, {
            /**
             * @cfg {String} url (Optional) The default URL to be used for requests to the server. Defaults to undefined.
             * The url config may be a function which returns the URL to use for the Ajax request. The scope
             * (this reference) of the function is the scope option passed to the {@link #request} method.
             */
            /**
             * @cfg {Object} extraParams (Optional) An object containing properties which are used as
             * extra parameters to each request made by this object. (defaults to undefined)
             */
            /**
             * @cfg {Object} defaultHeaders (Optional) An object containing request headers which are added
             *  to each request made by this object. (defaults to undefined)
             */
            /**
             * @cfg {String} method (Optional) The default HTTP method to be used for requests.
             * (defaults to undefined; if not set, but {@link #request} params are present, POST will be used;
             * otherwise, GET will be used.)
             */
            /**
             * @cfg {Number} timeout (Optional) The timeout in milliseconds to be used for requests. (defaults to 30000)
             */
            timeout : 30000,
            /**
             * @cfg {Boolean} autoAbort (Optional) Whether this request should abort any pending requests. (defaults to false)
             * @type Boolean
             */
            autoAbort:false,

            /**
             * @cfg {Boolean} disableCaching (Optional) True to add a unique cache-buster param to GET requests. (defaults to true)
             * @type Boolean
             */
            disableCaching: true,

            /**
             * @cfg {String} disableCachingParam (Optional) Change the parameter which is sent went disabling caching
             * through a cache buster. Defaults to '_dc'
             * @type String
             */
            disableCachingParam: '_dc',

            /**
             * Sends an HTTP request to a remote server.
             * Important: Ajax server requests are asynchronous, and this call will
             * return before the response has been received. Process any returned data
             * in a callback function.
             *
    Ext.Ajax.request({
       url: 'ajax_demo/sample.json',
       success: function(response, opts) {
          var obj = Ext.decode(response.responseText);
          console.dir(obj);
       },
       failure: function(response, opts) {
          console.log('server-side failure with status code ' + response.status);
       }
    });
             *
             * To execute a callback function in the correct scope, use the scope option.
             * @param {Object} options An object which may contain the following properties:
             * url : String/Function (Optional)The URL to
             * which to send the request, or a function to call which returns a URL string. The scope of the
             * function is specified by the scope option. Defaults to the configured
             * {@link #url}.
             * params : Object/String/Function (Optional)
             * An object containing properties which are used as parameters to the
             * request, a url encoded string or a function to call to get either. The scope of the function
             * is specified by the scope option.
             * method : String (Optional)The HTTP method to use
             * for the request. Defaults to the configured method, or if no method was configured,
             * "GET" if no parameters are being sent, and "POST" if parameters are being sent.  Note that
             * the method name is case-sensitive and should be all caps.
             * callback : Function (Optional)The
             * function to be called upon receipt of the HTTP response. The callback is
             * called regardless of success or failure and is passed the following
             * parameters:
             * options : ObjectThe parameter to the request call.
             * success : BooleanTrue if the request succeeded.
             * response : ObjectThe XMLHttpRequest object containing the response data.
             * See http://www.w3.org/TR/XMLHttpRequest/ for details about
             * accessing elements of the response.
             *
             * success : Function (Optional)The function
             * to be called upon success of the request. The callback is passed the following
             * parameters:
             * response : ObjectThe XMLHttpRequest object containing the response data.
             * options : ObjectThe parameter to the request call.
             *
             * failure : Function (Optional)The function
             * to be called upon failure of the request. The callback is passed the
             * following parameters:
             * response : ObjectThe XMLHttpRequest object containing the response data.
             * options : ObjectThe parameter to the request call.
             *
             * scope : Object (Optional)The scope in
             * which to execute the callbacks: The "this" object for the callback function. If the url, or params options were
             * specified as functions from which to draw values, then this also serves as the scope for those function calls.
             * Defaults to the browser window.
             * timeout : Number (Optional)The timeout in milliseconds to be used for this request. Defaults to 30 seconds.
             * form : Element/HTMLElement/String (Optional)The <form>
             * Element or the id of the <form> to pull parameters from.
             * isUpload : Boolean (Optional)Only meaningful when used
             * with the form option.
             * True if the form object is a file upload (will be set automatically if the form was
             * configured with enctype "multipart/form-data").
             * File uploads are not performed using normal "Ajax" techniques, that is they are not
             * performed using XMLHttpRequests. Instead the form is submitted in the standard manner with the
             * DOM <form> element temporarily modified to have its
             * target set to refer
             * to a dynamically generated, hidden <iframe> which is inserted into the document
             * but removed after the return data has been gathered.
             * The server response is parsed by the browser to create the document for the IFRAME. If the
             * server is using JSON to send the return object, then the
             * Content-Type header
             * must be set to "text/html" in order to tell the browser to insert the text unchanged into the document body.
             * The response text is retrieved from the document, and a fake XMLHttpRequest object
             * is created containing a responseText property in order to conform to the
             * requirements of event handlers and callbacks.
             * Be aware that file upload packets are sent with the content type multipart/form
             * and some server technologies (notably JEE) may require some custom processing in order to
             * retrieve parameter names and parameter values from the packet content.
             *
             * headers : Object (Optional)Request
             * headers to set for the request.
             * xmlData : Object (Optional)XML document
             * to use for the post. Note: This will be used instead of params for the post
             * data. Any params will be appended to the URL.
             * jsonData : Object/String (Optional)JSON
             * data to use as the post. Note: This will be used instead of params for the post
             * data. Any params will be appended to the URL.
             * disableCaching : Boolean (Optional)True
             * to add a unique cache-buster param to GET requests.
             *
             * The options object may also contain any other property which might be needed to perform
             * postprocessing in a callback because it is passed to callback functions.
             * @return {Number} transactionId The id of the server transaction. This may be used
             * to cancel the request.
             */
            request : function(o){
                var me = this;
                if(me.fireEvent(BEFOREREQUEST, me, o)){
                    if (o.el) {
                        if(!Ext.isEmpty(o.indicatorText)){
                            me.indicatorText = ''+o.indicatorText+"";
                        }
                        if(me.indicatorText) {
                            Ext.getDom(o.el).innerHTML = me.indicatorText;
                        }
                        o.success = (Ext.isFunction(o.success) ? o.success : function(){}).createInterceptor(function(response) {
                            Ext.getDom(o.el).innerHTML = response.responseText;
                        });
                    }

                    var p = o.params,
                        url = o.url || me.url,
                        method,
                        cb = {success: handleResponse,
                              failure: handleFailure,
                              scope: me,
                              argument: {options: o},
                              timeout : o.timeout || me.timeout
                        },
                        form,
                        serForm;

                    if (Ext.isFunction(p)) {
                        p = p.call(o.scope||WINDOW, o);
                    }

                    p = Ext.urlEncode(me.extraParams, Ext.isObject(p) ? Ext.urlEncode(p) : p);

                    if (Ext.isFunction(url)) {
                        url = url.call(o.scope || WINDOW, o);
                    }

                    if((form = Ext.getDom(o.form))){
                        url = url || form.action;
                         if(o.isUpload || /multipart\/form-data/i.test(form.getAttribute("enctype"))) {
                             return doFormUpload.call(me, o, p, url);
                         }
                        serForm = Ext.lib.Ajax.serializeForm(form);
                        p = p ? (p + '&' + serForm) : serForm;
                    }

                    method = o.method || me.method || ((p || o.xmlData || o.jsonData) ? POST : GET);

                    if(method === GET && (me.disableCaching && o.disableCaching !== false) || o.disableCaching === true){
                        var dcp = o.disableCachingParam || me.disableCachingParam;
                        url = Ext.urlAppend(url, dcp + '=' + (new Date().getTime()));
                    }

                    o.headers = Ext.apply(o.headers || {}, me.defaultHeaders || {});

                    if(o.autoAbort === true || me.autoAbort) {
                        me.abort();
                    }

                    if((method == GET || o.xmlData || o.jsonData) && p){
                        url = Ext.urlAppend(url, p);
                        p = '';
                    }
                    return (me.transId = Ext.lib.Ajax.request(method, url, cb, p, o));
                }else{
                    return o.callback ? o.callback.apply(o.scope, [o,UNDEFINED,UNDEFINED]) : null;
                }
            },

            /**
             * Determine whether this object has a request outstanding.
             * @param {Number} transactionId (Optional) defaults to the last transaction
             * @return {Boolean} True if there is an outstanding request.
             */
            isLoading : function(transId){
                return transId ? Ext.lib.Ajax.isCallInProgress(transId) : !! this.transId;
            },

            /**
             * Aborts any outstanding request.
             * @param {Number} transactionId (Optional) defaults to the last transaction
             */
            abort : function(transId){
                if(transId || this.isLoading()){
                    Ext.lib.Ajax.abort(transId || this.transId);
                }
            }
        });
    })();

    /**
     * @class Ext.Ajax
     * @extends Ext.data.Connection
     * The global Ajax request class that provides a simple way to make Ajax requests
     * with maximum flexibility.
     * Since Ext.Ajax is a singleton, you can set common properties/events for it once
     * and override them at the request function level only if necessary.
     * Common Properties you may want to set are:
     * {@link #method}
     * {@link #extraParams}
     * {@link #url}
     *
     *
    // Default headers to pass in every request
    Ext.Ajax.defaultHeaders = {
        'Powered-By': 'Ext'
    };
     *
     *
     * Common Events you may want to set are:
     * {@link Ext.data.Connection#beforerequest beforerequest}
     * {@link Ext.data.Connection#requestcomplete requestcomplete}
     * {@link Ext.data.Connection#requestexception requestexception}
     *
     *
    // Example: show a spinner during all Ajax requests
    Ext.Ajax.on('beforerequest', this.showSpinner, this);
    Ext.Ajax.on('requestcomplete', this.hideSpinner, this);
    Ext.Ajax.on('requestexception', this.hideSpinner, this);
     *
     *
     * An example request:
     *
    // Basic request
    Ext.Ajax.{@link Ext.data.Connection#request request}({
       url: 'foo.php',
       success: someFn,
       failure: otherFn,
       headers: {
           'my-header': 'foo'
       },
       params: { foo: 'bar' }
    });

    // Simple ajax form submission
    Ext.Ajax.{@link Ext.data.Connection#request request}({
        form: 'some-form',
        params: 'foo=bar'
    });
     *
     *
     * @singleton
     */
    Ext.Ajax = new Ext.data.Connection({
        /**
         * @cfg {String} url @hide
         */
        /**
         * @cfg {Object} extraParams @hide
         */
        /**
         * @cfg {Object} defaultHeaders @hide
         */
        /**
         * @cfg {String} method (Optional) @hide
         */
        /**
         * @cfg {Number} timeout (Optional) @hide
         */
        /**
         * @cfg {Boolean} autoAbort (Optional) @hide
         */

        /**
         * @cfg {Boolean} disableCaching (Optional) @hide
         */

        /**
         * @property  disableCaching
         * True to add a unique cache-buster param to GET requests. (defaults to true)
         * @type Boolean
         */
        /**
         * @property  url
         * The default URL to be used for requests to the server. (defaults to undefined)
         * If the server receives all requests through one URL, setting this once is easier than
         * entering it on every request.
         * @type String
         */
        /**
         * @property  extraParams
         * An object containing properties which are used as extra parameters to each request made
         * by this object (defaults to undefined). Session information and other data that you need
         * to pass with each request are commonly put here.
         * @type Object
         */
        /**
         * @property  defaultHeaders
         * An object containing request headers which are added to each request made by this object
         * (defaults to undefined).
         * @type Object
         */
        /**
         * @property  method
         * The default HTTP method to be used for requests. Note that this is case-sensitive and
         * should be all caps (defaults to undefined; if not set but params are present will use
         * "POST", otherwise will use "GET".)
         * @type String
         */
        /**
         * @property  timeout
         * The timeout in milliseconds to be used for requests. (defaults to 30000)
         * @type Number
         */

        /**
         * @property  autoAbort
         * Whether a new request should abort any pending requests. (defaults to false)
         * @type Boolean
         */
        autoAbort : false,

        /**
         * Serialize the passed form into a url encoded string
         * @param {String/HTMLElement} form
         * @return {String}
         */
        serializeForm : function(form){
            return Ext.lib.Ajax.serializeForm(form);
        }
    });