JavaScriptSerializer.Deserialize - 如何更改字段名称

Question

简介:在使用JavaScriptSerializer.Deserialize时,如何将JSON数据中的字段名称映射到.Net对象的字段名称？

更长版本:我从服务器API(未在.Net中编码)向我发送以下JSON数据

{"user_id":1234, "detail_level":"low"}

我有以下C#对象:

[Serializable]
public class DataObject
{
    [XmlElement("user_id")]
    public int UserId { get; set; }

    [XmlElement("detail_level")]
    public DetailLevel DetailLevel { get; set; }
}

其中DetailLevel是一个枚举,其中"低"作为其中一个值.

此测试失败:

[TestMethod]
public void DataObjectSimpleParseTest()
{
    JavaScriptSerializer serializer = new JavaScriptSerializer();
    DataObject dataObject = serializer.Deserialize<DataObject>(JsonData);

    Assert.IsNotNull(dataObject);
    Assert.AreEqual(DetailLevel.Low, dataObject.DetailLevel);
    Assert.AreEqual(1234, dataObject.UserId);
}

最后两个断言失败,因为这些字段中没有数据.如果我将JSON数据更改为

 {"userid":1234, "detaillevel":"low"}

然后它通过.但我不能改变服务器的行为,我希望客户端类在C#语言中具有良好命名的属性.我不能使用LINQ to JSON,因为我希望它在Silverlight之外工作.看起来XmlElement标签没有任何效果.我不知道我在哪里知道它们是相关的,它们可能不是.

你如何在JavaScriptSerializer中进行字段名称映射？它可以完成吗？

Answer 1

我使用DataContractJsonSerializer类再次尝试它.这解决了它:

代码如下所示:

using System.Runtime.Serialization;

[DataContract]
public class DataObject
{
    [DataMember(Name = "user_id")]
    public int UserId { get; set; }

    [DataMember(Name = "detail_level")]
    public string DetailLevel { get; set; }
}

测试是:

using System.Runtime.Serialization.Json;

[TestMethod]
public void DataObjectSimpleParseTest()
{
        DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(DataObject));

        MemoryStream ms = new MemoryStream(Encoding.Unicode.GetBytes(JsonData));
        DataObject dataObject = serializer.ReadObject(ms) as DataObject;

        Assert.IsNotNull(dataObject);
        Assert.AreEqual("low", dataObject.DetailLevel);
        Assert.AreEqual(1234, dataObject.UserId);
}

唯一的缺点是我必须将DetailLevel从枚举更改为字符串 - 如果保持枚举类型,DataContractJsonSerializer期望读取数值并失败.有关更多详细信息,请参阅DataContractJsonSerializer和Enums.

在我看来,这是非常差的,特别是当JavaScriptSerializer正确处理它时.这是您尝试将字符串解析为枚举的例外:

System.Runtime.Serialization.SerializationException: There was an error deserializing the object of type DataObject. The value 'low' cannot be parsed as the type 'Int64'. --->
System.Xml.XmlException: The value 'low' cannot be parsed as the type 'Int64'. --->  
System.FormatException: Input string was not in a correct format

并且像这样标记枚举不会改变这种行为:

[DataContract]
public enum DetailLevel
{
    [EnumMember(Value = "low")]
    Low,
   ...
 }

这似乎也适用于Silverlight.

Answer 2

通过创建自定义JavaScriptConverter,您可以将任何名称映射到任何属性.但它确实需要手工编码地图,这不太理想.

public class DataObjectJavaScriptConverter : JavaScriptConverter
{
    private static readonly Type[] _supportedTypes = new[]
    {
        typeof( DataObject )
    };

    public override IEnumerable<Type> SupportedTypes 
    { 
        get { return _supportedTypes; } 
    }

    public override object Deserialize( IDictionary<string, object> dictionary, 
                                        Type type, 
                                        JavaScriptSerializer serializer )
    {
        if( type == typeof( DataObject ) )
        {
            var obj = new DataObject();
            if( dictionary.ContainsKey( "user_id" ) )
                obj.UserId = serializer.ConvertToType<int>( 
                                           dictionary["user_id"] );
            if( dictionary.ContainsKey( "detail_level" ) )
                obj.DetailLevel = serializer.ConvertToType<DetailLevel>(
                                           dictionary["detail_level"] );

            return obj;
        }

        return null;
    }

    public override IDictionary<string, object> Serialize( 
            object obj, 
            JavaScriptSerializer serializer )
    {
        var dataObj = obj as DataObject;
        if( dataObj != null )
        {
            return new Dictionary<string,object>
            {
                {"user_id", dataObj.UserId },
                {"detail_level", dataObj.DetailLevel }
            }
        }
        return new Dictionary<string, object>();
    }
}

然后你可以这样反序列化:

var serializer = new JavaScriptSerializer();
serialzer.RegisterConverters( new[]{ new DataObjectJavaScriptConverter() } );
var dataObj = serializer.Deserialize<DataObject>( json );

Answer 3

Json.NET会做你想要的.它支持读取DataContract/DataMember属性以及它自己的属性来更改属性名称.另外还有StringEnumConverter类,用于将枚举值序列化为名称而不是数字.

Answer 4

对于重命名属性没有标准支持,JavaScriptSerializer但是您可以非常轻松地添加自己的属性:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Script.Serialization;
using System.Reflection;

public class JsonConverter : JavaScriptConverter
{
    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
    {
        List<MemberInfo> members = new List<MemberInfo>();
        members.AddRange(type.GetFields());
        members.AddRange(type.GetProperties().Where(p => p.CanRead && p.CanWrite && p.GetIndexParameters().Length == 0));

        object obj = Activator.CreateInstance(type);

        foreach (MemberInfo member in members)
        {
            JsonPropertyAttribute jsonProperty = (JsonPropertyAttribute)Attribute.GetCustomAttribute(member, typeof(JsonPropertyAttribute));

            if (jsonProperty != null && dictionary.ContainsKey(jsonProperty.Name))
            {
                SetMemberValue(serializer, member, obj, dictionary[jsonProperty.Name]);
            }
            else if (dictionary.ContainsKey(member.Name))
            {
                SetMemberValue(serializer, member, obj, dictionary[member.Name]);
            }
            else
            {
                KeyValuePair<string, object> kvp = dictionary.FirstOrDefault(x => string.Equals(x.Key, member.Name, StringComparison.InvariantCultureIgnoreCase));

                if (!kvp.Equals(default(KeyValuePair<string, object>)))
                {
                    SetMemberValue(serializer, member, obj, kvp.Value);
                }
            }
        }

        return obj;
    }


    private void SetMemberValue(JavaScriptSerializer serializer, MemberInfo member, object obj, object value)
    {
        if (member is PropertyInfo)
        {
            PropertyInfo property = (PropertyInfo)member;                
            property.SetValue(obj, serializer.ConvertToType(value, property.PropertyType), null);
        }
        else if (member is FieldInfo)
        {
            FieldInfo field = (FieldInfo)member;
            field.SetValue(obj, serializer.ConvertToType(value, field.FieldType));
        }
    }


    public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
    {
        Type type = obj.GetType();
        List<MemberInfo> members = new List<MemberInfo>();
        members.AddRange(type.GetFields());
        members.AddRange(type.GetProperties().Where(p => p.CanRead && p.CanWrite && p.GetIndexParameters().Length == 0));

        Dictionary<string, object> values = new Dictionary<string, object>();

        foreach (MemberInfo member in members)
        {
            JsonPropertyAttribute jsonProperty = (JsonPropertyAttribute)Attribute.GetCustomAttribute(member, typeof(JsonPropertyAttribute));

            if (jsonProperty != null)
            {
                values[jsonProperty.Name] = GetMemberValue(member, obj);
            }
            else
            {
                values[member.Name] = GetMemberValue(member, obj);
            }
        }

        return values;
    }

    private object GetMemberValue(MemberInfo member, object obj)
    {
        if (member is PropertyInfo)
        {
            PropertyInfo property = (PropertyInfo)member;
            return property.GetValue(obj, null);
        }
        else if (member is FieldInfo)
        {
            FieldInfo field = (FieldInfo)member;
            return field.GetValue(obj);
        }

        return null;
    }


    public override IEnumerable<Type> SupportedTypes
    {
        get 
        {
            return new[] { typeof(DataObject) };
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class JsonPropertyAttribute : Attribute
{
    public JsonPropertyAttribute(string name)
    {
        Name = name;
    }

    public string Name
    {
        get;
        set;
    }
}

DataObject然后该课程成为:

public class DataObject
{
    [JsonProperty("user_id")]
    public int UserId { get; set; }

    [JsonProperty("detail_level")]
    public DetailLevel DetailLevel { get; set; }
}

我认为这可能有点晚,但认为其他人想要使用JavaScriptSerializer而不是DataContractJsonSerializer可能会欣赏它.

Answer 5

创建一个继承自JavaScriptConverter的类.然后你必须实现三件事:

方法-

1. 连载
2. 反序列化

属性-

1. SupportedTypes

当您需要对序列化和反序列化过程进行更多控制时,可以使用JavaScriptConverter类.

JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.RegisterConverters(new JavaScriptConverter[] { new MyCustomConverter() });

DataObject dataObject = serializer.Deserialize<DataObject>(JsonData);

这是一个链接以获取更多信息

Answer 6

我使用了下面的 Newtonsoft.Json。创建一个对象：

 public class WorklistSortColumn
  {
    [JsonProperty(PropertyName = "field")]
    public string Field { get; set; }

    [JsonProperty(PropertyName = "dir")]
    public string Direction { get; set; }

    [JsonIgnore]
    public string SortOrder { get; set; }
  }

现在调用下面的方法序列化为 Json 对象，如下所示。

string sortColumn = JsonConvert.SerializeObject(worklistSortColumn);