The source code

    /**
     * @class Ext.form.Action
     * The subclasses of this class provide actions to perform upon {@link Ext.form.BasicForm Form}s.
     * Instances of this class are only created by a {@link Ext.form.BasicForm Form} when
     * the Form needs to perform an action such as submit or load. The Configuration options
     * listed for this class are set through the Form's action methods: {@link Ext.form.BasicForm#submit submit},
     * {@link Ext.form.BasicForm#load load} and {@link Ext.form.BasicForm#doAction doAction}
     * The instance of Action which performed the action is passed to the success
     * and failure callbacks of the Form's action methods ({@link Ext.form.BasicForm#submit submit},
     * {@link Ext.form.BasicForm#load load} and {@link Ext.form.BasicForm#doAction doAction}),
     * and to the {@link Ext.form.BasicForm#actioncomplete actioncomplete} and
     * {@link Ext.form.BasicForm#actionfailed actionfailed} event handlers.
     */
    Ext.form.Action = function(form, options){
        this.form = form;
        this.options = options || {};
    };

    /**
     * Failure type returned when client side validation of the Form fails
     * thus aborting a submit action. Client side validation is performed unless
     * {@link #clientValidation} is explicitly set to false.
     * @type {String}
     * @static
     */
    Ext.form.Action.CLIENT_INVALID = 'client';
    /**
     * Failure type returned when server side processing fails and the {@link #result}'s
     * success property is set to false.
     * In the case of a form submission, field-specific error messages may be returned in the
     * {@link #result}'s errors property.
     * @type {String}
     * @static
     */
    Ext.form.Action.SERVER_INVALID = 'server';
    /**
     * Failure type returned when a communication error happens when attempting
     * to send a request to the remote server. The {@link #response} may be examined to
     * provide further information.
     * @type {String}
     * @static
     */
    Ext.form.Action.CONNECT_FAILURE = 'connect';
    /**
     * Failure type returned when the response's success
     * property is set to false, or no field values are returned in the response's
     * data property.
     * @type {String}
     * @static
     */
    Ext.form.Action.LOAD_FAILURE = 'load';

    Ext.form.Action.prototype = {
    /**
     * @cfg {String} url The URL that the Action is to invoke.
     */
    /**
     * @cfg {Boolean} reset When set to true, causes the Form to be
     * {@link Ext.form.BasicForm.reset reset} on Action success. If specified, this happens
     * before the {@link #success} callback is called and before the Form's
     * {@link Ext.form.BasicForm.actioncomplete actioncomplete} event fires.
     */
    /**
     * @cfg {String} method The HTTP method to use to access the requested URL. Defaults to the
     * {@link Ext.form.BasicForm}'s method, or if that is not specified, the underlying DOM form's method.
     */
    /**
     * @cfg {Mixed} params Extra parameter values to pass. These are added to the Form's
     * {@link Ext.form.BasicForm#baseParams} and passed to the specified URL along with the Form's
     * input fields.
     * Parameters are encoded as standard HTTP parameters using {@link Ext#urlEncode}.
     */
    /**
     * @cfg {Number} timeout The number of seconds to wait for a server response before
     * failing with the {@link #failureType} as {@link #Action.CONNECT_FAILURE}. If not specified,
     * defaults to the configured {@link Ext.form.BasicForm#timeout timeout} of the
     * {@link Ext.form.BasicForm form}.
     */
    /**
     * @cfg {Function} success The function to call when a valid success return packet is recieved.
     * The function is passed the following parameters:
     * form : Ext.form.BasicFormThe form that requested the action
     * action : Ext.form.ActionThe Action class. The {@link #result}
     * property of this object may be examined to perform custom postprocessing.
     *
     */
    /**
     * @cfg {Function} failure The function to call when a failure packet was recieved, or when an
     * error ocurred in the Ajax communication.
     * The function is passed the following parameters:
     * form : Ext.form.BasicFormThe form that requested the action
     * action : Ext.form.ActionThe Action class. If an Ajax
     * error ocurred, the failure type will be in {@link #failureType}. The {@link #result}
     * property of this object may be examined to perform custom postprocessing.
     *
     */
    /**
     * @cfg {Object} scope The scope in which to call the callback functions (The this reference
     * for the callback functions).
     */
    /**
     * @cfg {String} waitMsg The message to be displayed by a call to {@link Ext.MessageBox#wait}
     * during the time the action is being processed.
     */
    /**
     * @cfg {String} waitTitle The title to be displayed by a call to {@link Ext.MessageBox#wait}
     * during the time the action is being processed.
     */

    /**
     * The type of action this Action instance performs.
     * Currently only "submit" and "load" are supported.
     * @type {String}
     */
        type : 'default',
    /**
     * The type of failure detected will be one of these: {@link #CLIENT_INVALID},
     * {@link #SERVER_INVALID}, {@link #CONNECT_FAILURE}, or {@link #LOAD_FAILURE}.  Usage:
     *
    var fp = new Ext.form.FormPanel({
    ...
    buttons: [{
        text: 'Save',
        formBind: true,
        handler: function(){
            if(fp.getForm().isValid()){
                fp.getForm().submit({
                    url: 'form-submit.php',
                    waitMsg: 'Submitting your data...',
                    success: function(form, action){
                        // server responded with success = true
                        var result = action.{@link #result};
                    },
                    failure: function(form, action){
                        if (action.{@link #failureType} === Ext.form.Action.{@link #CONNECT_FAILURE}) {
                            Ext.Msg.alert('Error',
                                'Status:'+action.{@link #response}.status+': '+
                                action.{@link #response}.statusText);
                        }
                        if (action.failureType === Ext.form.Action.{@link #SERVER_INVALID}){
                            // server responded with success = false
                            Ext.Msg.alert('Invalid', action.{@link #result}.errormsg);
                        }
                    }
                });
            }
        }
    },{
        text: 'Reset',
        handler: function(){
            fp.getForm().reset();
        }
    }]
     *
     * @property failureType
     * @type {String}
     */
     /**
     * The XMLHttpRequest object used to perform the action.
     * @property response
     * @type {Object}
     */
     /**
     * The decoded response object containing a boolean success property and
     * other, action-specific properties.
     * @property result
     * @type {Object}
     */

        // interface method
        run : function(options){

        },

        // interface method
        success : function(response){

        },

        // interface method
        handleResponse : function(response){

        },

        // default connection failure
        failure : function(response){
            this.response = response;
            this.failureType = Ext.form.Action.CONNECT_FAILURE;
            this.form.afterAction(this, false);
        },

        // private
        // shared code among all Actions to validate that there was a response
        // with either responseText or responseXml
        processResponse : function(response){
            this.response = response;
            if(!response.responseText && !response.responseXML){
                return true;
            }
            this.result = this.handleResponse(response);
            return this.result;
        },

        // utility functions used internally
        getUrl : function(appendParams){
            var url = this.options.url || this.form.url || this.form.el.dom.action;
            if(appendParams){
                var p = this.getParams();
                if(p){
                    url = Ext.urlAppend(url, p);
                }
            }
            return url;
        },

        // private
        getMethod : function(){
            return (this.options.method || this.form.method || this.form.el.dom.method || 'POST').toUpperCase();
        },

        // private
        getParams : function(){
            var bp = this.form.baseParams;
            var p = this.options.params;
            if(p){
                if(typeof p == "object"){
                    p = Ext.urlEncode(Ext.applyIf(p, bp));
                }else if(typeof p == 'string' && bp){
                    p += '&' + Ext.urlEncode(bp);
                }
            }else if(bp){
                p = Ext.urlEncode(bp);
            }
            return p;
        },

        // private
        createCallback : function(opts){
            var opts = opts || {};
            return {
                success: this.success,
                failure: this.failure,
                scope: this,
                timeout: (opts.timeout*1000) || (this.form.timeout*1000),
                upload: this.form.fileUpload ? this.success : undefined
            };
        }
    };

    /**
     * @class Ext.form.Action.Submit
     * @extends Ext.form.Action
     * A class which handles submission of data from {@link Ext.form.BasicForm Form}s
     * and processes the returned response.
     * Instances of this class are only created by a {@link Ext.form.BasicForm Form} when
     * {@link Ext.form.BasicForm#submit submit}ting.
     * Response Packet Criteria
     * A response packet may contain:
     *
     * success property : Boolean
     * The success property is required.
     * errors property : Object
     * The errors property,
     * which is optional, contains error messages for invalid fields.
     *
     * JSON Packets
     * By default, response packets are assumed to be JSON, so a typical response
     * packet may look like this:
    {
        success: false,
        errors: {
            clientCode: "Client not found",
            portOfLoading: "This field must not be null"
        }
    }
     * Other data may be placed into the response for processing by the {@link Ext.form.BasicForm}'s callback
     * or event handler methods. The object decoded from this JSON is available in the
     * {@link Ext.form.Action#result result} property.
     * Alternatively, if an {@link #errorReader} is specified as an {@link Ext.data.XmlReader XmlReader}:
        errorReader: new Ext.data.XmlReader({
                record : 'field',
                success: '@success'
            }, [
                'id', 'msg'
            ]
        )

     * then the results may be sent back in XML format:
    <?xml version="1.0" encoding="UTF-8"?>
    <message success="false">
    <errors>
        <field>
            <id>clientCode</id>
            <msg><![CDATA[Code not found. <br /><i>This is a test validation message from the server </i>]]></msg>
        </field>
        <field>
            <id>portOfLoading</id>
            <msg><![CDATA[Port not found. <br /><i>This is a test validation message from the server </i>]]></msg>
        </field>
    </errors>
    </message>

     * Other elements may be placed into the response XML for processing by the {@link Ext.form.BasicForm}'s callback
     * or event handler methods. The XML document is available in the {@link #errorReader}'s {@link Ext.data.XmlReader#xmlData xmlData} property.
     */
    Ext.form.Action.Submit = function(form, options){
        Ext.form.Action.Submit.superclass.constructor.call(this, form, options);
    };

    Ext.extend(Ext.form.Action.Submit, Ext.form.Action, {
        /**
         * @cfg {Ext.data.DataReader} errorReader Optional. JSON is interpreted with
         * no need for an errorReader.
         * A Reader which reads a single record from the returned data. The DataReader's
         * success property specifies how submission success is determined. The Record's
         * data provides the error messages to apply to any invalid form Fields.
         */
        /**
         * @cfg {boolean} clientValidation Determines whether a Form's fields are validated
         * in a final call to {@link Ext.form.BasicForm#isValid isValid} prior to submission.
         * Pass false in the Form's submit options to prevent this. If not defined, pre-submission field validation
         * is performed.
         */
        type : 'submit',

        // private
        run : function(){
            var o = this.options;
            var method = this.getMethod();
            var isGet = method == 'GET';
            if(o.clientValidation === false || this.form.isValid()){
                Ext.Ajax.request(Ext.apply(this.createCallback(o), {
                    form:this.form.el.dom,
                    url:this.getUrl(isGet),
                    method: method,
                    headers: o.headers,
                    params:!isGet ? this.getParams() : null,
                    isUpload: this.form.fileUpload
                }));
            }else if (o.clientValidation !== false){ // client validation failed
                this.failureType = Ext.form.Action.CLIENT_INVALID;
                this.form.afterAction(this, false);
            }
        },

        // private
        success : function(response){
            var result = this.processResponse(response);
            if(result === true || result.success){
                this.form.afterAction(this, true);
                return;
            }
            if(result.errors){
                this.form.markInvalid(result.errors);
                this.failureType = Ext.form.Action.SERVER_INVALID;
            }
            this.form.afterAction(this, false);
        },

        // private
        handleResponse : function(response){
            if(this.form.errorReader){
                var rs = this.form.errorReader.read(response);
                var errors = [];
                if(rs.records){
                    for(var i = 0, len = rs.records.length; i < len; i++) {
                        var r = rs.records[i];
                        errors[i] = r.data;
                    }
                }
                if(errors.length < 1){
                    errors = null;
                }
                return {
                    success : rs.success,
                    errors : errors
                };
            }
            return Ext.decode(response.responseText);
        }
    });

    /**
     * @class Ext.form.Action.Load
     * @extends Ext.form.Action
     * A class which handles loading of data from a server into the Fields of an {@link Ext.form.BasicForm}.
     * Instances of this class are only created by a {@link Ext.form.BasicForm Form} when
     * {@link Ext.form.BasicForm#load load}ing.
     * Response Packet Criteria
     * A response packet must contain:
     *
     * success property : Boolean
     * data property : Object
     * The data property contains the values of Fields to load.
     * The individual value object for each Field is passed to the Field's
     * {@link Ext.form.Field#setValue setValue} method.
     *
     * JSON Packets
     * By default, response packets are assumed to be JSON, so for the following form load call:
    var myFormPanel = new Ext.form.FormPanel({
        title: 'Client and routing info',
        items: [{
            fieldLabel: 'Client',
            name: 'clientName'
        }, {
            fieldLabel: 'Port of loading',
            name: 'portOfLoading'
        }, {
            fieldLabel: 'Port of discharge',
            name: 'portOfDischarge'
        }]
    });
    myFormPanel.{@link Ext.form.FormPanel#getForm getForm}().{@link Ext.form.BasicForm#load load}({
        url: '/getRoutingInfo.php',
        params: {
            consignmentRef: myConsignmentRef
        },
        failure: function(form, action() {
            Ext.Msg.alert("Load failed", action.result.errorMessage);
        }
    });

     * a success response packet may look like this:
    {
        success: true,
        data: {
            clientName: "Fred. Olsen Lines",
            portOfLoading: "FXT",
            portOfDischarge: "OSL"
        }
    }
     * while a failure response packet may look like this:
    {
        success: false,
        errorMessage: "Consignment reference not found"
    }
     * Other data may be placed into the response for processing the {@link Ext.form.BasicForm Form}'s
     * callback or event handler methods. The object decoded from this JSON is available in the
     * {@link Ext.form.Action#result result} property.
     */
    Ext.form.Action.Load = function(form, options){
        Ext.form.Action.Load.superclass.constructor.call(this, form, options);
        this.reader = this.form.reader;
    };

    Ext.extend(Ext.form.Action.Load, Ext.form.Action, {
        // private
        type : 'load',

        // private
        run : function(){
            Ext.Ajax.request(Ext.apply(
                    this.createCallback(this.options), {
                        method:this.getMethod(),
                        url:this.getUrl(false),
                        headers: this.options.headers,
                        params:this.getParams()
            }));
        },

        // private
        success : function(response){
            var result = this.processResponse(response);
            if(result === true || !result.success || !result.data){
                this.failureType = Ext.form.Action.LOAD_FAILURE;
                this.form.afterAction(this, false);
                return;
            }
            this.form.clearInvalid();
            this.form.setValues(result.data);
            this.form.afterAction(this, true);
        },

        // private
        handleResponse : function(response){
            if(this.form.reader){
                var rs = this.form.reader.read(response);
                var data = rs.records && rs.records[0] ? rs.records[0].data : null;
                return {
                    success : rs.success,
                    data : data
                };
            }
            return Ext.decode(response.responseText);
        }
    });

    /**
     * @class Ext.form.Action.DirectLoad
     * @extends Ext.form.Action.Load
     * Provides Ext.direct support for loading form data. This example illustrates usage
     * of Ext.Direct to load a submit a form through Ext.Direct.
     *
    var myFormPanel = new Ext.form.FormPanel({
        // configs for FormPanel
        title: 'Basic Information',
        border: false,
        padding: 10,
        buttons:[{
            text: 'Submit',
            handler: function(){
                basicInfo.getForm().submit({
                    params: {
                        uid: 5
                    }
                });
            }
        }],

        // configs apply to child items
        defaults: {anchor: '100%'},
        defaultType: 'textfield',
        items: [
            // form fields go here
        ],

        // configs for BasicForm
        api: {
            load: Profile.getBasicInfo,
            // The server-side must mark the submit handler as a 'formHandler'
            submit: Profile.updateBasicInfo
        },
        paramOrder: ['uid']
    });

    // load the form
    myFormPanel.getForm().load({
        params: {
            uid: 5
        }
    });
     *
     */
    Ext.form.Action.DirectLoad = Ext.extend(Ext.form.Action.Load, {
        constructor: function(form, opts) {
            Ext.form.Action.DirectLoad.superclass.constructor.call(this, form, opts);
        },
        type: 'directload',

        run : function(){
            var args = this.getParams();
            args.push(this.success, this);
            this.form.api.load.apply(window, args);
        },

        getParams: function() {
            var buf = [], o = {};
            var bp = this.form.baseParams;
            var p = this.options.params;
            Ext.apply(o, p, bp);
            var paramOrder = this.form.paramOrder;
            if(paramOrder){
                for(var i = 0, len = paramOrder.length; i < len; i++){
                    buf.push(o[paramOrder[i]]);
                }
            }else if(this.form.paramsAsHash){
                buf.push(o);
            }
            return buf;
        },
        // Direct actions have already been processed and therefore
        // we can directly set the result; Direct Actions do not have
        // a this.response property.
        processResponse: function(result) {
            this.result = result;
            return result;
        }
    });

    /**
     * @class Ext.form.Action.DirectSubmit
     * @extends Ext.form.Action.Submit
     * Provides Ext.direct support for submitting form data.
     * See {@link Ext.form.Action.DirectLoad}.
     */
    Ext.form.Action.DirectSubmit = Ext.extend(Ext.form.Action.Submit, {
        constructor: function(form, opts) {
            Ext.form.Action.DirectSubmit.superclass.constructor.call(this, form, opts);
        },
        type: 'directsubmit',
        // override of Submit
        run : function(){
            var o = this.options;
            if(o.clientValidation === false || this.form.isValid()){
                // tag on any additional params to be posted in the
                // form scope
                this.success.params = this.getParams();
                this.form.api.submit(this.form.el.dom, this.success, this);
            }else if (o.clientValidation !== false){ // client validation failed
                this.failureType = Ext.form.Action.CLIENT_INVALID;
                this.form.afterAction(this, false);
            }
        },

        getParams: function() {
            var o = {};
            var bp = this.form.baseParams;
            var p = this.options.params;
            Ext.apply(o, p, bp);
            return o;
        },
        // Direct actions have already been processed and therefore
        // we can directly set the result; Direct Actions do not have
        // a this.response property.
        processResponse: function(result) {
            this.result = result;
            return result;
        }
    });

    Ext.form.Action.ACTION_TYPES = {
        'load' : Ext.form.Action.Load,
        'submit' : Ext.form.Action.Submit,
        'directload': Ext.form.Action.DirectLoad,
        'directsubmit': Ext.form.Action.DirectSubmit
    };