在.Net的MVC开发中，经常会使用到Json对象，于是，系统提供了JsonResult这个对象，其本质是调用.Net系统自带的Json序列化类JavaScriptSerializer对数据对象进行序列化。但是这个系统自带的Json序列化对象方法没有Json.Net好用，于是打算有些时候用Json.Net替代默认的实现。
要实现有时候用Json.Net，有时候用默认实现，那么就要保证系统中两种实现并存。对于Server将对象序列化成Json传给Client很简单，我们只需要建立一个新的ActionResult，我们命名为JsonNetResult，然后在Get时，return这个JsonNetResult即可。JsonNetResult的代码实现为：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text; namespace MvcJsonNet
{
using System.IO;
using System.Web;
using System.Web.Mvc;
using Newtonsoft.Json; public class JsonNetResult : JsonResult
{
public JsonNetResult()
{
Settings = new JsonSerializerSettings
{
ReferenceLoopHandling = ReferenceLoopHandling.Error
};
}
public JsonNetResult(object data, JsonRequestBehavior behavior = JsonRequestBehavior.AllowGet, string contentType=null, Encoding contentEncoding=null)
{
this.Data = data;
this.JsonRequestBehavior = behavior;
this.ContentEncoding = contentEncoding;
this.ContentType = contentType;
} public JsonSerializerSettings Settings { get; private set; } public override void ExecuteResult(ControllerContext context)
{ if (context == null)
throw new ArgumentNullException("context");
if (this.JsonRequestBehavior == JsonRequestBehavior.DenyGet && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
throw new InvalidOperationException("JSON GET is not allowed"); HttpResponseBase response = context.HttpContext.Response;
response.ContentType = string.IsNullOrEmpty(this.ContentType) ? "application/json" : this.ContentType; if (this.ContentEncoding != null)
response.ContentEncoding = this.ContentEncoding;
if (this.Data == null)
return; var scriptSerializer = JsonSerializer.Create(this.Settings); using (var sw = new StringWriter())
{
scriptSerializer.Serialize(sw, this.Data);
response.Write(sw.ToString());
}
}
}
}
要返回一个Json.Net序号列后的对象，那么调用方法是：
[HttpGet]
public ActionResult GetJsonNet()
{
var myClass = InitClass();
return new JsonNetResult(myClass);
}
这是Get方法，但是对于ClientPost一个Json回Server，那么就比较麻烦了，需要修改好几处地方：
1，建立Json.Net的ValueProviderFactory，这个类主要就是用于Json字符串的反序列化。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web; namespace MvcJsonNet
{
using System.Collections;
using System.Dynamic;
using System.Globalization;
using System.IO;
using System.Web.Mvc;
using System.Web.Script.Serialization;
using Newtonsoft.Json; public class JsonNetValueProviderFactory : ValueProviderFactory
{
private void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
} IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
} // primitive
backingStore[prefix] = value;
} private object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.InvariantCultureIgnoreCase))
{
// not JSON request
return null;
} StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
//接下来的代码是关键，判断content type，如果是json.net，那么就使用Json.Net的反序列化方法，如果不是，那么就使用系统默认的反序列化方法
if (controllerContext.HttpContext.Request.ContentType.StartsWith("application/json.net", StringComparison.InvariantCultureIgnoreCase))
{
var jsonData = JsonConvert.DeserializeObject<ExpandoObject>(bodyText);
return jsonData;
}
else
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
} public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
} object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
} Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
} private string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
} private string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
}
2，在初始化MVC时替换掉默认的JsonValueProviderFactory。
在Global.asax的Application_Start时，写入以下代码：
ValueProviderFactories.Factories.Remove(ValueProviderFactories.Factories.OfType<JsonValueProviderFactory>().FirstOrDefault());
ValueProviderFactories.Factories.Add(new JsonNetValueProviderFactory());
3，建立新的ModelBinder，命名为JsonNetModelBinder。
namespace MvcJsonNet
{
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Web.Mvc;
using Newtonsoft.Json; public class JsonNetModelBinder : DefaultModelBinder
{
protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext,
PropertyDescriptor propertyDescriptor)
{
Debug.WriteLine("BindProperty");
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json.net",
StringComparison
.InvariantCultureIgnoreCase))
{
//根据Content type来判断，只有json.net这种content type的才会使用该ModelBinder，否则使用默认的Binder
base.BindProperty(controllerContext, bindingContext, propertyDescriptor);
return;
} // need to skip properties that aren't part of the request, else we might hit a *Exception
string name = propertyDescriptor.Name;
foreach (object attribute in propertyDescriptor.Attributes)
{
if (attribute is JsonPropertyAttribute)
{
var jp = attribute as JsonPropertyAttribute;
name = jp.PropertyName;
}
} string fullPropertyKey = CreateSubPropertyName(bindingContext.ModelName, name);
if (!bindingContext.ValueProvider.ContainsPrefix(fullPropertyKey))
{
return;
} // call into the property's model binder
IModelBinder propertyBinder = Binders.GetBinder(propertyDescriptor.PropertyType);
object originalPropertyValue = propertyDescriptor.GetValue(bindingContext.Model);
ModelMetadata propertyMetadata = bindingContext.PropertyMetadata[propertyDescriptor.Name];
propertyMetadata.Model = originalPropertyValue;
var innerBindingContext = new ModelBindingContext
{
ModelMetadata = propertyMetadata,
ModelName = fullPropertyKey,
ModelState = bindingContext.ModelState,
ValueProvider = bindingContext.ValueProvider
};
object newPropertyValue = GetPropertyValue(controllerContext, innerBindingContext, propertyDescriptor,
propertyBinder);
propertyMetadata.Model = newPropertyValue; // validation
ModelState modelState = bindingContext.ModelState[fullPropertyKey];
if (modelState == null || modelState.Errors.Count == 0)
{
if (OnPropertyValidating(controllerContext, bindingContext, propertyDescriptor, newPropertyValue))
{
SetProperty(controllerContext, bindingContext, propertyDescriptor, newPropertyValue);
OnPropertyValidated(controllerContext, bindingContext, propertyDescriptor, newPropertyValue);
}
}
else
{
SetProperty(controllerContext, bindingContext, propertyDescriptor, newPropertyValue); // Convert FormatExceptions (type conversion failures) into InvalidValue messages
foreach (
ModelError error in
modelState.Errors.Where(err => String.IsNullOrEmpty(err.ErrorMessage) && err.Exception != null)
.ToList())
{
for (Exception exception = error.Exception; exception != null; exception = exception.InnerException)
{
if (exception is FormatException)
{
string displayName = propertyMetadata.GetDisplayName();
string errorMessageTemplate = "The value '{0}' is not valid for {1}.";
string errorMessage = String.Format(CultureInfo.CurrentCulture, errorMessageTemplate,
modelState.Value.AttemptedValue, displayName);
modelState.Errors.Remove(error);
modelState.Errors.Add(errorMessage);
break;
}
}
}
}
}
}
}
4，建立一个VModel的基类，为该基类添加Attribute，然后在Global中添加Model和Binder的映射。
[ModelBinder(typeof (JsonNetModelBinder))]
public abstract class VEntity
{
public virtual long Id { get; set; }
}
Global.asax中Application_Start添加代码：
ModelBinders.Binders.Add(typeof(VEntity), new JsonNetModelBinder());
5在前端Post Json时，指定content type为application/json.net
function PostJsonNet() {
var jsonstr = $("#jsonstring")[0].innerHTML;
$.ajax({
url: "MyTest/CreateFromJsonNet",
type: "POST",
data: jsonstr,
contentType: "application/json.net",
dataType: "json",
success: function (data) {
alert(data);
}
});
}
我们这样处理后，Client在往Server传送Json数据时，如果指定了contentType是application/json，那么就使用系统默认的方法来反序列化对象，如果是application/json.net，那么就使用Json.Net来反序列化。