转：Asp.net Ajax WebService 实现循环引用(自定义JavascriptConverter)

文章转自：http://www.cnblogs.com/Henllyee/archive/2008/07/18/1246161.html

准备技术：
    1.简单的WebService编写；
    2.了解Asp.net Ajax 客户端访问WebService
内容：
    asp.net ajax框架在去年看过，只是些基本的使用，并没有过多的去研究它的原理。最近在一个项目中要实现客户端访问WebService并返回DataTable类型的数据，当我调用一个返回DataTable的方法时，不能返回成功，在错误的回调函数中告诉我DataTable是一个循环应用类型，不能序列化。当是想过把DataTable替换成其他类型的数据如ArrayList或则Array等,可是有点心不甘，所以查过各个方面的资料，告诉我微软已经提供了一个解决DataTable的JavaScriptConverter的dll文件，当我在web.config中添加了对这个JavascriptConverter引用即可以将DataTable序列化成Json字符串了。
    好了，废话不多说了。下面就自己来做个循环应用的实例，并通过自定义JavascriptConverter来解决循环引用的问题。本文只会简单的介绍下服务器端序列化数据类型到Json的过程，不会太深入。

首先先来定义两个类，想了半天最好的实例就是一对夫妻，一个老公只有一个老婆，这是婚姻法规定的，所以老公类型跟老婆类型就可以达到实例中的循环引用。看下两个类型的类试图：

其实两个类里面的内容都很简单,Husband.cs:

using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.ComponentModel;

public class Husband
{
    private string _firstName;

    public string FirstName
    {
        get { return _firstName; }
        set { _firstName = value; }
    }
    private string _lastName;

    public string LastName
    {
        get { return _lastName; }
        set { _lastName = value; }
    }
    private Wife _wife;

    public Wife Wife
    {
        get { return _wife; }
        set { _wife = value; }
    }
}

Wife.cs：

using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.ComponentModel;

public class Wife
{
    private string _firstName;

    public string FirstName
    {
        get { return _firstName; }
        set { _firstName = value; }
    }
    private string _lastName;

    public string LastName
    {
        get { return _lastName; }
        set { _lastName = value; }
    }
    private Husband _husband;

    public Husband Husband
    {
        get { return _husband; }
        set { _husband = value; }
    }
}

然后我定义了个Webservice类用来提供Client的访问，HusbandService.cs:

using System;
using System.Collections;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Xml.Linq;
using System.Web.Script.Services;

/**//// <summary>
/// Husband's Method
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ScriptService]
public class HusbandService : System.Web.Services.WebService {

    public HusbandService () {

        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public Husband GetHusband()
    {
        Husband hansband = new Husband();
        hansband.FirstName = "Henllyee";
        hansband.LastName = "Cui";
        Wife wife = new Wife();
        wife.FirstName = "Throwen";
        wife.LastName = "Yang";

        hansband.Wife = wife;
        wife.Husband = hansband;

        return hansband;
    }
    
}

我在一个asp.net 页面中通过asp.net ajax对GetHusband()的应用的，JavascriptConverter.aspx：

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="JavascriptConverter.aspx.cs" Inherits="_Default" %>

<!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 runat="server">
    <title>JavaScriptConverter Demo</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="scriptManager" runat="server">
            <Services>
                <asp:ServiceReference Path="~/HusbandService.asmx" />
            </Services>
        </asp:ScriptManager>
        <script language="javascript" type="text/javascript">
          function getServiceHasband()
          {
            HusbandService.GetHusband(onSuccess,onFailed);
          }
          function onSuccess(result)
          {
            alert(result.FirstName);
          }
          function onFailed(error)
          {
            alert(error.get_message());
          }
          
          
          window.onload=function()
          {
            var btnGet = $get("btnGet");
            if(btnGet)
            {
                btnGet.onclick=getServiceHasband;
            }  
          }
        </script>
        <input type="button" id="btnGet" value="Get HusBand" />
    </div>
    </form>
</body>
</html>

运行后当我们点击按钮是，会弹出出错的信息，告诉我们Husband是一个循环引用类型，不能序列化。这时我们可以通过编写对应的JavascriptConverter来告诉服务器端如何去序列化。

我们自定的JavascriptConverter必须继承于JavascriptConverter(JavascriptConverter参考文档)，然后去重写里面的两个方法跟一个属性：
1.Deserialize:如何反序列化一个Jason到这个Converter类型；
2.Serialize：如何序列化支持的对象到一个Jason；
3.SupportedTypes：这个Converter支持的类型。
好了下面我们定义下一个Converter来支持循环引用，现在我们先定义如何将去序列化，HusbandConverter.cs：

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Web.Script.Serialization;
using System.Collections.Generic;

/**//// <summary>
/// Husband's Converter
/// </summary>
public class HusbandConverter:JavaScriptConverter
{
    public HusbandConverter()
    {
        
    }

    /**//// <summary>
    /// 
    /// </summary>
    /// <param name="dictionary"></param>
    /// <param name="type"></param>
    /// <param name="serializer"></param>
    /// <returns></returns>
    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
    {
        throw new NotImplementedException();
    }
    
    /**//// <summary>
    /// Serizlize a json
    /// </summary>
    /// <param name="obj"></param>
    /// <param name="serializer"></param>
    /// <returns></returns>
    public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
    {
        Husband husband = (Husband)obj;
        IDictionary<string,object> dictionary  = new Dictionary<string,object>();
        husband.Wife.Husband = null;
        dictionary["FirstName"] = husband.FirstName;
        dictionary["LastName"] = husband.LastName;
        dictionary["Wife"] = husband.Wife;

        return dictionary;
    }

    /**//// <summary>
    /// Support Types
    /// </summary>
    public override System.Collections.Generic.IEnumerable<Type> SupportedTypes
    {
        get
        {
            yield return typeof(Husband);
        }
    }
}

然后我们在web.config中注册这样一段对这个Converter的引用:

<system.web.extensions>
        <scripting>
            <webServices>
                <jsonSerialization>
                    <converters>
                        <add name="HusbandConvert" type="HusbandConverter,App_Code"/>
                    </converters>
                </jsonSerialization>
            </webServices>
        </scripting>
    </system.web.extensions>

这下我们再运行时，去点击按钮就能返回“Henllyee”。
在上面中我们首先重写了SupportedTypes属性去告诉系统我这个Converter支持那些类型的数据。然后我们去重写了Serialize方法，其实我们在这里只是把husband.Wife.Husband设置为了null,让它不去循环引用了，所以这样就破坏原来的类的本意。但是我们可以在客户端再去完善它，再在客户端设置husband.Wife.Husband=husband即可了。
下面我们再看如何进行反序列化了。首先我们在webservice中先添加一个方法，来传入Husband对象

[WebMethod]
    public string GetHusbandInfo(Husband hansband)
    {
        Debug.Assert(hansband.Wife.Husband == hansband);

        return String.Format(
            "Husband's :{0}\n Wife:{1}",
            hansband.FirstName + " " + hansband.LastName,
            hansband.Wife.FirstName + " " + hansband.LastName);
    }

然后我们再去把反序列化实现下：

public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
    {
        Husband husband = new Husband();
        husband.FirstName = (string)dictionary["FirstName"];
        husband.LastName = (string)dictionary["LastName"];
        husband.Wife = serializer.ConvertToType<Wife>(dictionary["Wife"]);
        husband.Wife.Husband = husband;
        return husband;
    }

最后我们在客户端进行调用

function getHusbandInfo()
          {
            var husband = new Object();
            husband.FirstName="Henllyee";
            husband.LastName="Cui";
            var wif = new Object();
            wif.FirstName="Erry";
            wif.LastName="Du";
            husband.Wife=wif;
            HusbandService.GetHusbandInfo(husband,onGetInfoSucceded,onFailed);
          }
          
          function onGetInfoSucceded(result)
          {
            alert(result);
          }

通过运行我们会发现反序列化是成功的。

posted on 2012-08-17 16:22 追@风阅读(162) 评论(0) 收藏举报

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