The source code

    /**
     * @class Ext.data.DirectProxy
     * @extends Ext.data.DataProxy
     */
    Ext.data.DirectProxy = function(config){
        Ext.apply(this, config);
        if(typeof this.paramOrder == 'string'){
            this.paramOrder = this.paramOrder.split(/[\s,|]/);
        }
        Ext.data.DirectProxy.superclass.constructor.call(this, config);
    };

    Ext.extend(Ext.data.DirectProxy, Ext.data.DataProxy, {
        /**
         * @cfg {Array/String} paramOrder Defaults to undefined. A list of params to be executed
         * server side.  Specify the params in the order in which they must be executed on the server-side
         * as either (1) an Array of String values, or (2) a String of params delimited by either whitespace,
         * comma, or pipe. For example,
         * any of the following would be acceptable:
    paramOrder: ['param1','param2','param3']
    paramOrder: 'param1 param2 param3'
    paramOrder: 'param1,param2,param3'
    paramOrder: 'param1|param2|param'

         */
        paramOrder: undefined,

        /**
         * @cfg {Boolean} paramsAsHash
         * Send parameters as a collection of named arguments (defaults to true). Providing a
         * {@link #paramOrder} nullifies this configuration.
         */
        paramsAsHash: true,

        /**
         * @cfg {Function} directFn
         * Function to call when executing a request.  directFn is a simple alternative to defining the api configuration-parameter
         * for Store's which will not implement a full CRUD api.
         */
        directFn : undefined,

        // protected
        doRequest : function(action, rs, params, reader, callback, scope, options) {
            var args = [];
            var directFn = this.api[action] || this.directFn;

            switch (action) {
                case Ext.data.Api.actions.create:
                    args.push(params[reader.meta.root]);		// <-- create(Hash)
                    break;
                case Ext.data.Api.actions.read:
                    if(this.paramOrder){
                        for(var i = 0, len = this.paramOrder.length; i < len; i++){
                            args.push(params[this.paramOrder[i]]);
                        }
                    }else if(this.paramsAsHash){
                        args.push(params);
                    }
                    break;
                case Ext.data.Api.actions.update:
                    args.push(params[reader.meta.idProperty]);  // <-- save(Integer/Integer[], Hash/Hash[])
                    args.push(params[reader.meta.root]);
                    break;
                case Ext.data.Api.actions.destroy:
                    args.push(params[reader.meta.root]);        // <-- destroy(Int/Int[])
                    break;
            }

            var trans = {
                params : params || {},
                request: {
                    callback : callback,
                    scope : scope,
                    arg : options
                },
                reader: reader
            };

            args.push(this.createCallback(action, rs, trans), this);
            directFn.apply(window, args);
        },

        // private
        createCallback : function(action, rs, trans) {
            return function(result, res) {
                if (!res.status) {
                    // @deprecated fire loadexception
                    if (action === Ext.data.Api.actions.read) {
                        this.fireEvent("loadexception", this, trans, res, null);
                    }
                    this.fireEvent('exception', this, 'remote', action, trans, res, null);
                    trans.request.callback.call(trans.request.scope, null, trans.request.arg, false);
                    return;
                }
                if (action === Ext.data.Api.actions.read) {
                    this.onRead(action, trans, result, res);
                } else {
                    this.onWrite(action, trans, result, res, rs);
                }
            };
        },
        /**
         * Callback for read actions
         * @param {String} action [Ext.data.Api.actions.create|read|update|destroy]
         * @param {Object} trans The request transaction object
         * @param {Object} res The server response
         * @private
         */
        onRead : function(action, trans, result, res) {
            var records;
            try {
                records = trans.reader.readRecords(result);
            }
            catch (ex) {
                // @deprecated: Fire old loadexception for backwards-compat.
                this.fireEvent("loadexception", this, trans, res, ex);

                this.fireEvent('exception', this, 'response', action, trans, res, ex);
                trans.request.callback.call(trans.request.scope, null, trans.request.arg, false);
                return;
            }
            this.fireEvent("load", this, res, trans.request.arg);
            trans.request.callback.call(trans.request.scope, records, trans.request.arg, true);
        },
        /**
         * Callback for write actions
         * @param {String} action [Ext.data.Api.actions.create|read|update|destroy]
         * @param {Object} trans The request transaction object
         * @param {Object} res The server response
         * @private
         */
        onWrite : function(action, trans, result, res, rs) {
            this.fireEvent("write", this, action, result, res, rs, trans.request.arg);
            trans.request.callback.call(trans.request.scope, result, res, true);
        }
    });