extjs form加载数据无法执行success:function

[didoleo]

cityForm.getForm().load({
waitMsg : '正在加载数据',
waitTitle : '提示',
url : 'load4UpdateCity.action?ids=' + cityEditId,
method : 'post',
success:function(form, action) {
Ext.Msg.alert('提示', "加载成功!"); // 这里执行不到，为什么
}
,
failure:function(form, action){
//Ext.getCmp("addCity.name").setValue("天津");
Ext.Msg.alert('提示', '加载失败1');
}
});


////////////////////////////////////////////////

后台返回的json字符串是：
{"map":{"addCity.pid":4,"addCity.name":"石家庄","addCity.pycode":"shijiazhuang","addCity.areacode":"310000","addCity.postcode":"201138","addCity.pname":"石家庄"},"success":true}

[Go 旅城通票]

少了data属性吧，不是map属性 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 setValue method.