ExtJs学习笔记(23)-ScriptTagProxy+XTemplate+WCF跨域取数据

ajax应用中跨域一直是一个非常麻烦的问题，目前也有一些解决办法，但要么比较麻烦，要么就不具备通用性，幸好ExtJs里的ScriptTagProxy提供了跨域读取数据的功能，而且在几大浏览器上都可以正常运行，但在使用过程中要注意几点:

1.服务端返回时，必须按以下格式返回:

stcCallback1001({...})

其中stcCallback1001中的1001是自动生成的，如果是分页提交的话，每再请求一次1001会变成1002,1003...类推

2.ExtJs官方的示例中虽然ScriptTagProxy的例子并不少，但是就是没有XTemplate+ScriptTagProxy跨域读取的单一功能示例，下面给一个XTemplate跨域读取数据的示例

a.服务端WCF的处理

Code
[OperationContract]
    [WebInvoke(ResponseFormat = WebMessageFormat.Json, UriTemplate = "GetData3?start={start}&limit={limit}&callback={callback}", Method = "*")]
    public Stream GetData3(int start, int limit,string CallBack)
    {
        System.Threading.Thread.Sleep(1000);//为演示Ajax加载效果，停1秒

        List<T_GuestBook> _List = new List<T_GuestBook>();
        _List.Add(new T_GuestBook() { F_ID = 1, F_IP = "192.23.37.41", F_Date = DateTime.Now, F_Content = "这是第一条留言", F_Reply = "" });
        _List.Add(new T_GuestBook() { F_ID = 2, F_IP = "192.168.0.1", F_Date = DateTime.Now, F_Content = "这是第二条留言", F_Reply = "" });
        _List.Add(new T_GuestBook() { F_ID = 3, F_IP = "192.168.0.2", F_Date = DateTime.Now, F_Content = "这是第三条留言", F_Reply = "" });
        _List.Add(new T_GuestBook() { F_ID = 4, F_IP = "172.168.235.1", F_Date = DateTime.Now, F_Content = "这是第四条留言", F_Reply = "" });
        _List.Add(new T_GuestBook() { F_ID = 5, F_IP = "10.200.30.4", F_Date = DateTime.Now, F_Content = "这是第五条留言", F_Reply = "" });
        _List.Add(new T_GuestBook() { F_ID = 6, F_IP = "10.200.30.5", F_Date = DateTime.Now, F_Content = "这是第六条留言", F_Reply = "" });
        //以上操作也可以改为利用Linq直接从数据库读取                   


        PageData<List<T_GuestBook>> _PageData = new PageData<List<T_GuestBook>>();

        _PageData.RecordCount = _List.Count;

        int PageSize = limit;

        if (PageSize <= 0) { PageSize = 1; }
        if (PageSize > _PageData.RecordCount) { PageSize = _PageData.RecordCount; }
        _PageData.PageSize = PageSize;

        //计算总页数
        if (_PageData.RecordCount % _PageData.PageSize == 0)
        {
            _PageData.PageCount = (_PageData.RecordCount / _PageData.PageSize);
        }
        else
        {
            _PageData.PageCount = (_PageData.RecordCount / _PageData.PageSize) + 1;
        }

        int PageIndex = (start/limit) + 1;

        if (PageIndex <= 0) { PageIndex = 1; }
        if (PageIndex > _PageData.PageCount) { PageIndex = _PageData.PageCount; }

        _PageData.CurrentPageIndex = PageIndex;

        List<T_GuestBook> _List2 = _List.Skip(start).Take(limit).ToList();//取得当前页数据

        _PageData.Data = _List2;


        string returnStr = CallBack + "(" + JavaScriptConvert.SerializeObject(_PageData) +")";
        MemoryStream ms = new MemoryStream();
        StreamWriter sw = new StreamWriter(ms);
        sw.AutoFlush = true;
        sw.Write(returnStr);
        ms.Position = 0;
        WebOperationContext.Current.OutgoingResponse.ContentType = "text/plain";

        return ms;
    }

这里与上一篇http://www.cnblogs.com/yjmyzz/archive/2008/09/10/1288399.html (ExtJs学习笔记(22)-XTemplate + WCF 打造无刷新数据分页)相比，多了一个参数callBack，同时返回类型改为Stream，返回方法的处理参考了老张的http://www.cnblogs.com/jillzhang/archive/2008/07/17/1245458.html(再说ExtJs与WCF之间的跨域访问)一文

b.ExtJs的前端处理

Code
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <link type="text/css" rel="Stylesheet"  href="../resources/css/ext-all.css" />
    <script type="text/javascript" src="../adapter/ext/ext-base.js"></script>
    <script type="text/javascript" src="../ext-all-debug.js"></script>
    <style type="text/css">        *{font-size: 9pt;line-height: 120%;}        .red{color: Red;}        h1{font-size:16px;}    </style>    
</head>
<body>

<script type="text/javascript">
    Ext.onReady(function() {
        var proxy = new Ext.data.ScriptTagProxy({
        url: 'http://ext.cneds.net/WCF/MyService.svc/GetData3'

        //服务端的返回值类似:
        //stcCallback1001({"RecordCount":6,"PageSize":2,"PageCount":3,"CurrentPageIndex":2,"Data":[{"F_ID":3,"F_IP":"192.168.0.2","F_Date":new Date(1221399073843),"F_Content":"这是第三条留言","F_Reply":""},{"F_ID":4,"F_IP":"172.168.235.1","F_Date":new Date(1221399073843),"F_Content":"这是第四条留言","F_Reply":""}]})
        //其中stcCallback1001中的1001是自动生成的，如果是分页提交的话，每再请求一次1001会变成1002,1003类推
        
        });
        var reader = new Ext.data.JsonReader(
         { root: 'Data', totalProperty: 'RecordCount' },
         [
           { name: 'F_ID' },
           { name: 'F_IP' },
           { name: 'F_Date' },
           { name: 'F_Content' }
         ]
       );

        var tpl = new Ext.XTemplate(
        '<table width="100%">',
        '<tpl for="data">', //表明这里开始循环
       '<tr><td style="font-weight:bold;color:#666">网友[{F_IP}] {F_Date} 说:</td></tr>', '<tr><td>　　{F_Content}</td></tr>', '<tr><td><hr style="height:1px"/></td></tr>',
        '</tpl>', //循环结束
        '</table>'
        );

        var oGrid = Ext.get("page-grid");

        //回调函数
        function callback(data, arg, success) {
            if (success) {
                var _returnStr = Ext.util.JSON.encode(data);
                //{"success":true,"records":[{"id":1001,"data":{"F_ID":3,"F_IP":"192.168.0.2","F_Date":"2008-09-14T21:28:28","F_Content":"这是第三条留言"},"json":{"F_ID":3,"F_IP":"192.168.0.2","F_Date":"2008-09-14T21:28:28","F_Content":"这是第三条留言","F_Reply":""}},{"id":1002,"data":{"F_ID":4,"F_IP":"172.168.235.1","F_Date":"2008-09-14T21:28:28","F_Content":"这是第四条留言"},"json":{"F_ID":4,"F_IP":"172.168.235.1","F_Date":"2008-09-14T21:28:28","F_Content":"这是第四条留言","F_Reply":""}}],"totalRecords":6}
                //服务端将返回类似上面的字符串，无法直接跟xTemplate绑定，需要转换一下
                
                var oReg = /\"json\":({.*?})/gi;
                var oResult = _returnStr.match(oReg);
                var s = "";
                for (var i = 0; i < oResult.length; i++) {
                    oResult[i].match(oReg);
                    s += RegExp.$1 + ",";
                }
                if (s.length != 0) { s = s.substr(0, s.length - 1); }
                s = "{data:[" + s + "]}";
                //最终将转换成
                //{data:[{"F_ID":3,"F_IP":"192.168.0.2","F_Date":"2008-09-14T21:29:55","F_Content":"这是第三条留言","F_Reply":""},{"F_ID":4,"F_IP":"172.168.235.1","F_Date":"2008-09-14T21:29:55","F_Content":"这是第四条留言","F_Reply":""}]}
                var data = eval("(" + s + ")");
                tpl.overwrite("page-grid", data);
            }
        }

        oGrid.dom.innerHTML = "加载中";
        
        proxy.load({ start: 2, limit: 2 }, reader, callback, this);
    });
</script>

<div id="page-grid"></div>
</body>
</html>

这里要注意的是:

尝试了多次，发现XTemplate不支持多层节点的绑定，即服务端返回的值类似：

stcCallback1001({"RecordCount":6,"PageSize":2,"PageCount":3,"CurrentPageIndex":2,"Data":[{"F_ID":3,"F_IP":"192.168.0.2","F_Date":new Date(1221399073843),"F_Content":"这是第三条留言","F_Reply":""},{"F_ID":4,"F_IP":"172.168.235.1","F_Date":new Date(1221399073843),"F_Content":"这是第四条留言","F_Reply":""}]})

在回调函数里经过Ext.util.JSON.encode(data)处理后，变成了

{"success":true,"records":[{"id":1001,"data":{"F_ID":3,"F_IP":"192.168.0.2","F_Date":"2008-09-14T21:28:28","F_Content":"这是第三条留言"},"json":

{"F_ID":3,"F_IP":"192.168.0.2","F_Date":"2008-09-14T21:28:28","F_Content":"这是第三条留言","F_Reply":""}},{"id":1002,"data":{"F_ID":4,"F_IP":"172.168.235.1","F_Date":"2008

-09-14T21:28:28","F_Content":"这是第四条留言"},"json":{"F_ID":4,"F_IP":"172.168.235.1","F_Date":"2008-09-14T21:28:28","F_Content":"这是第四条留

言","F_Reply":""}}],"totalRecords":6}

虽然也是标准的JSON字符串，但是数据节点是多层次的，XTemplate无法直接读取。所以只能在客户端用JS的正则表达式处理，手动重新组织成XTemplate所需的JSON对象，最终转换成：

{data:[{"F_ID":3,"F_IP":"192.168.0.2","F_Date":"2008-09-14T21:29:55","F_Content":"这是第三条留言","F_Reply":""},{"F_ID":4,"F_IP":"172.168.235.1","F_Date":"2008-09-14T21:29:55","F_Content":"这是第四条留言","F_Reply":""}]}