S2SH、EXTJS、JSON调整后，EXTJS接收不到Struts2的Action传回的值，无语

Ext.onReady(function(){    var f = new Ext.form.FormPanel({            //数据传送到服务器的配置        url: "/BackOS/login.action",        method: "post",//        baseParams: {extra: "中华人民共和国", id: 100},        title: "欢迎登陆",        width: 300,        autoHeight: true,        bodyStyle: "padding: 6px",        labelAlign: "right",        defaultType: "textfield",//默认组件类型        frame: true,        items: [            new Ext.form.TextField({                name: "teller.tellerno",                allowBlank: false, //不允许为空                value: "000000",                fieldLabel: "用户名"            }),{                name: "teller.password",                inputType: "password",                value: "123456",                fieldLabel: "密码",                allowBlank: false //不允许为空            }        ],        buttons:[{            text: "确定",            handler: function(){                var userName = f.getForm().findField("teller.tellerno").getValue();                var password = f.getForm().findField("teller.password").getValue();//                Ext.Msg.alert("", "用户名：" + userName + "<br>密码：" + password);                            //提交表单                f.getForm().submit({                    success: function(f, action){                        Ext.Msg.alert("",action.responseText);//                        Ext.Msg.alert("成功", "恭喜，表单提交成功,服务器反馈的结果是：");                    },                    failure: function(){                        Ext.Msg.alert("失败", "对不起，表单提交失败");                    }                });            }        },        {            text: "重置",            handler: function(){                //f.getForm().reset();                var fields = f.getForm().items.items;                for(var i = 0; i < fields.length; i ++){                    fields[i].reset();                                    }            }        }]    });        f.render("login");})

public String execute() throws Exception {        HttpServletResponse response = ServletActionContext.getResponse();        response.setContentType("text/html;charset=utf-8");        if(itt.userLogin(teller)){            System.out.println("-------------1");            response.getWriter().println("{success:'true'}");            return SUCCESS;        }        else{//            response.getWriter().println("{success:false,msg:'失败登陆'}");            return SUCCESS;        }    }

<package name="nothing" extends="json-default">        <default-action-ref name="login" />        <action name="login" class="loginAction">            <result type="json"></result>        </action>    </package>