ext提交submit到action中,如何处理??????????

Ext.onReady(function(){    
          //使用表单提示
          Ext.QuickTips.init();
          Ext.form.Field.prototype.msgTarget = 'side';
          
          //定义表单
          var simple = new Ext.FormPanel({
                labelWidth: 75,             
                baseCls: 'x-plain',
                defaults: {width: 150},
                defaultType: 'textfield',//默认字段类型
                onSubmit: Ext.emptyFn, 
                submit: function() { 
                    //有疑问的地方 
                    this.getEl().dom.action='<%=basePath %>regist.do'; 
                    this.getEl().dom.submit(); 
                },  
                //定义表单元素
                items: [{
                        fieldLabel: '帐户',
                        name: 'username',//元素名称
                        //anchor:'95%',//也可用此定义自适应宽度
                        allowBlank:false,//不允许为空
                        blankText:'帐户不能为空'//错误提示内容
                    },{
                        inputType:'password',
                        fieldLabel: '密码',
                        //anchor:'95%',
                        name: 'password',
                        allowBlank:false,
                        blankText:'密码不能为空'
                    }
                ],                buttons: [{
                    text: '登陆',
                    type: 'submit',
                    //定义表单提交事件
                    handler:function(){
                              if(simple.form.isValid()){//验证合法后使用加载进度条
                                  Ext.MessageBox.show({
                                       title: '请稍等',
                                       msg: '正在加载...',
                                       progressText: '',
                                       width:300,
                                       progress:true,
                                       closable:false,
                                       animEl: 'loding'
                                   });
                                   //控制进度速度
                                   var f = function(v){
                                     return function(){
                                                var i = v/11;
                                                Ext.MessageBox.updateProgress(i, '');
                                            };
                                   };                                   for(var i = 1; i < 13; i++){
                                        setTimeout(f(i), i*150);
                                   }                        
                                  
                                  //提交到服务器操作
                                  simple.form.doAction('submit',{
                                     url:'<%=basePath%>regist.do',//文件路径
                                     method:'post',//提交方法post或get
                                     params:'',
                                     //提交成功的回调函数
                                     success:function(form,action){
                                            if (action.result.msg=='ok') {
                                                document.location='index.jsp';
                                            } else {
                                                Ext.Msg.alert('登陆错误',action.result.msg);
                                            }
                                     },
                                     //提交失败的回调函数
                                     failure:function(){
                                            Ext.Msg.alert('错误','服务器出现错误请稍后再试！');
                                     }
                                  });
                               }                                                          
                    }
                },{
                    text: '取消',
                    handler:function(){simple.form.reset();}//重置表单
                }]
            });    
                   //定义窗体
                   win = new Ext.Window({
                        id:'win',
                        title:'用户登陆',
                        layout:'fit',    //之前提到的布局方式fit，自适应布局                    
                        width:300,
                        height:150,
                        plain:true,
                        bodyStyle:'padding:5px;',
                        maximizable:false,//禁止最大化
                        closeAction:'close',
                        closable:false,//禁止关闭
                        collapsible:true,//可折叠
                        plain: true,
                        buttonAlign:'center',
                        items:simple//将表单作为窗体元素嵌套布局
                    });
                    win.show();//显示窗体
                                        
         });提交到action中,如何返回值到回调函数 
String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8"); 
String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8"); PrintWriter out=response.getWriter(); 
if(username.equals("admin") && password.equals("123")) { [color=#FF0000]//如何返回参数到JS 
} else { 
//如何返回参数到JS } 
return null;