Ext store 加载不到远程数据

大家帮我看看，为什么加载不到远程数据呀：Ext.onReady(function(){
    var Student = new Ext.data.Record.create([
        {name:'id'},
        {name:'name'},
        {name:'email'},
        {name:'sex'},
        {name:'bornDate',dateFormat:'Y年m月d日'}
    ]);
    var data = {"totalCount":"54671",'root':[{
        id:1,
        name:'小王',
        sex:'男',
        email:'[email protected]',
        bornDate:'1991-4-4'
    },{
        id:2,
        name:'小李',
        sex:'男',
        email:'[email protected]',
        bornDate:'1992-5-6'
    },{
        id:3,
        name:'小兰',
        sex:'女',
        email:'[email protected]',
        bornDate:'1993-3-7'
    }]};    var store = new Ext.data.Store({
    
        idProperty: 'id',
//     proxy:new Ext.data.MemoryProxy(data),
proxy : new Ext.data.HttpProxy({
url : 'ProductQueryAction.do?method=ShowAllAreaActionJSON'
}),
        reader:new Ext.data.JsonReader({
            root:'root',totalProperty:'totalCount'    //指定分页控件属性用,用于解决第二个问题
        },Student)
    });
    store.load(); //加载数据
    alert(store.getCount()+"****");
});
后台代码： areaString="{'totalCount':'54671','root':[{id:1,name:'小王',sex:'男',email:'[email protected]',bornDate:'1991-4-4'},{id:2,name:'小李',sex:'男',email:'[email protected]',bornDate:'1992-5-6'},{id:3,name:'小兰',sex:'女',email:'[email protected]',bornDate:'1993-3-7'}]}";
response.setContentType("application/x-json");
this.sendOutString(response, areaString);
如果我换成MemoryProxy，用上面的data的话，就可以加载到数据，但是换成HttpProxy，去后台就拿不到数据，不知道为什么！
麻烦大家帮忙看看！