• .NET MVC JSON JavaScriptSerializer 字符串的长度超过 maxJsonLength 值问题的解决


    1 [ArgumentException: 使用 JSON JavaScriptSerializer 序列化或还原序列化期间发生错误。字符串的长度超过在 maxJsonLength 属性上设定的值。
    2 参数名称: input]
    3    System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit) +168
    4    System.Web.Mvc.JsonValueProviderFactory.GetDeserializedObject(ControllerContext controllerContext) +213
    5    System.Web.Mvc.JsonValueProviderFactory.GetValueProvider(ControllerContext controllerContext) +16
    6    System.Web.Mvc.ValueProviderFactoryCollection.GetValueProvider(ControllerContext controllerContext) +69
    7    System.Web.Mvc.ControllerBase.get_ValueProvider() +30  

    于前端 Post 到 Action 的参数太大,超过了2M,还没进入后台的 Action 方法就报错了。这个问题困扰了很久,一直未解决。网上找了几个方法都无效。

    在 web.config 中加入这些,没有作用:

     
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    <appSettings>
      <add key="aspnet:MaxJsonDeserializerMembers" value="2147483647" />
      <add key="aspnet:UpdatePanelMaxScriptLength" value="2147483647" />
    </appSettings>

    在 web.config 中加入这些,也没有作用:

     
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    <system.web.extensions>
      <scripting>
        <webServices>
          <jsonSerialization maxJsonLength="2147483647">
          </jsonSerialization>
        </webServices>
      </scripting>
    </system.web.extensions>

    仔细看了一下异常信息,发现,是在System.Web.Mvc.JsonValueProviderFactory 里调用的 JavaScriptSerializer:

    于是查了一下 ,发现 JsonValueProviderFactory 在 System.Web.Mvc.dll 程序集里的:

    反编译 System.Web.Mvc.dll 找到 JsonValueProviderFactory 类:

     
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    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Collections.Specialized;
    using System.Configuration;
    using System.Globalization;
    using System.IO;
    using System.Web.Mvc.Properties;
    using System.Web.Script.Serialization;
    namespace System.Web.Mvc
    {
        public sealed class JsonValueProviderFactory : ValueProviderFactory
        {
            private class EntryLimitedDictionary
            {
                private static int _maximumDepth = JsonValueProviderFactory.EntryLimitedDictionary.GetMaximumDepth();
                private readonly IDictionary<string, object> _innerDictionary;
                private int _itemCount;
                public EntryLimitedDictionary(IDictionary<string, object> innerDictionary)
                {
                    this._innerDictionary = innerDictionary;
                }
                public void Add(string key, object value)
                {
                    if (++this._itemCount > JsonValueProviderFactory.EntryLimitedDictionary._maximumDepth)
                    {
                        throw new InvalidOperationException(MvcResources.JsonValueProviderFactory_RequestTooLarge);
                    }
                    this._innerDictionary.Add(key, value);
                }
                private static int GetMaximumDepth()
                {
                    NameValueCollection appSettings = ConfigurationManager.AppSettings;
                    if (appSettings != null)
                    {
                        string[] values = appSettings.GetValues("aspnet:MaxJsonDeserializerMembers");
                        int result;
                        if (values != null && values.Length > 0 && int.TryParse(values[0], out result))
                        {
                            return result;
                        }
                    }
                    return 1000;
                }
            }
            private static void AddToBackingStore(JsonValueProviderFactory.EntryLimitedDictionary backingStore, string prefix, object value)
            {
                IDictionary<string, object> dictionary = value as IDictionary<string, object>;
                if (dictionary != null)
                {
                    foreach (KeyValuePair<string, object> current in dictionary)
                    {
                        JsonValueProviderFactory.AddToBackingStore(backingStore, JsonValueProviderFactory.MakePropertyKey(prefix, current.Key), current.Value);
                    }
                    return;
                }
                IList list = value as IList;
                if (list != null)
                {
                    for (int i = 0; i < list.Count; i++)
                    {
                        JsonValueProviderFactory.AddToBackingStore(backingStore, JsonValueProviderFactory.MakeArrayKey(prefix, i), list[i]);
                    }
                    return;
                }
                backingStore.Add(prefix, value);
            }
            private static object GetDeserializedObject(ControllerContext controllerContext)
            {
                if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
                {
                    return null;
                }
                StreamReader streamReader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
                string text = streamReader.ReadToEnd();
                if (string.IsNullOrEmpty(text))
                {
                    return null;
                }
                // 问题就出在这里,没有给 javaScriptSerializer.MaxJsonLength 赋值,其默认值是 2097152 字节,即2M
                JavaScriptSerializer javaScriptSerializer = new JavaScriptSerializer();
                return javaScriptSerializer.DeserializeObject(text);
            }
            public override IValueProvider GetValueProvider(ControllerContext controllerContext)
            {
                if (controllerContext == null)
                {
                    throw new ArgumentNullException("controllerContext");
                }
                object deserializedObject = JsonValueProviderFactory.GetDeserializedObject(controllerContext);
                if (deserializedObject == null)
                {
                    return null;
                }
                Dictionary<string, object> dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
                JsonValueProviderFactory.EntryLimitedDictionary backingStore = new JsonValueProviderFactory.EntryLimitedDictionary(dictionary);
                JsonValueProviderFactory.AddToBackingStore(backingStore, string.Empty, deserializedObject);
                return new DictionaryValueProvider<object>(dictionary, CultureInfo.CurrentCulture);
            }
            private static string MakeArrayKey(string prefix, int index)
            {
                return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
            }
            private static string MakePropertyKey(string prefix, string propertyName)
            {
                if (!string.IsNullOrEmpty(prefix))
                {
                    return prefix + "." + propertyName;
                }
                return propertyName;
            }
        }
    }

    在 JavaScriptSerializer 没有设置 MaxJsonLength,默认值是 2097152 字节,即2M。 

    解决此问题的方法就是 把 javaScriptSerializer.MaxJsonLength = int.MaxValue; (int.MaxValue 值是 2147483647 字节,即2048M)

    自己重写类 JsonValueProviderFactory 命名为 MyJsonValueProviderFactory:

     
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    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Collections.Specialized;
    using System.Configuration;
    using System.Globalization;
    using System.IO;
    using System.Web.Mvc;
    using System.Web.Mvc.Properties;
    using System.Web.Script.Serialization;
    namespace XXX
    {
        public sealed class MyJsonValueProviderFactory : ValueProviderFactory
        {
            private class EntryLimitedDictionary
            {
                private static int _maximumDepth = GetMaximumDepth();
                private readonly IDictionary<string, object> _innerDictionary;
                private int _itemCount;
     
                public EntryLimitedDictionary(IDictionary<string, object> innerDictionary)
                {
                    this._innerDictionary = innerDictionary;
                }
     
                public void Add(string key, object value)
                {
                    if (++this._itemCount > _maximumDepth)
                    {
                        //throw new InvalidOperationException(MvcResources.JsonValueProviderFactory_RequestTooLarge);
                        throw new InvalidOperationException("itemCount is over maximumDepth");
                    }
                    this._innerDictionary.Add(key, value);
                }
     
                private static int GetMaximumDepth()
                {
                    NameValueCollection appSettings = ConfigurationManager.AppSettings;
                    if (appSettings != null)
                    {
                        string[] values = appSettings.GetValues("aspnet:MaxJsonDeserializerMembers");
                        int result;
                        if (values != null && values.Length > 0 && int.TryParse(values[0], out result))
                        {
                            return result;
                        }
                    }
                    return 1000;
                }
            }
     
            private static void AddToBackingStore(EntryLimitedDictionary backingStore, string prefix, object value)
            {
                IDictionary<string, object> dictionary = value as IDictionary<string, object>;
                if (dictionary != null)
                {
                    foreach (KeyValuePair<string, object> current in dictionary)
                    {
                        AddToBackingStore(backingStore, MakePropertyKey(prefix, current.Key), current.Value);
                    }
                    return;
                }
                IList list = value as IList;
                if (list != null)
                {
                    for (int i = 0; i < list.Count; i++)
                    {
                        AddToBackingStore(backingStore, MakeArrayKey(prefix, i), list[i]);
                    }
                    return;
                }
                backingStore.Add(prefix, value);
            }
     
            private static object GetDeserializedObject(ControllerContext controllerContext)
            {
                if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
                {
                    return null;
                }
                StreamReader streamReader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
                string text = streamReader.ReadToEnd();
                if (string.IsNullOrEmpty(text))
                {
                    return null;
                }
                JavaScriptSerializer javaScriptSerializer = new JavaScriptSerializer();
                // 解决这个问题:
                // 使用 JSON JavaScriptSerializer 序列化或还原序列化期间发生错误。字符串的长度超过在 maxJsonLength 属性上设定的值。
                javaScriptSerializer.MaxJsonLength = int.MaxValue;
                // ----------------------------------------
                return javaScriptSerializer.DeserializeObject(text);
            }
     
            public override IValueProvider GetValueProvider(ControllerContext controllerContext)
            {
                if (controllerContext == null)
                {
                    throw new ArgumentNullException("controllerContext");
                }
                object deserializedObject = GetDeserializedObject(controllerContext);
                if (deserializedObject == null)
                {
                    return null;
                }
                Dictionary<string, object> dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
                EntryLimitedDictionary backingStore = new EntryLimitedDictionary(dictionary);
                AddToBackingStore(backingStore, string.Empty, deserializedObject);
                return new DictionaryValueProvider<object>(dictionary, CultureInfo.CurrentCulture);
            }
     
            private static string MakeArrayKey(string prefix, int index)
            {
                return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
            }
     
            private static string MakePropertyKey(string prefix, string propertyName)
            {
                if (!string.IsNullOrEmpty(prefix))
                {
                    return prefix + "." + propertyName;
                }
                return propertyName;
            }
        }
    }

    然后在 Global.asax 中的 Application_Start() 方法里,加入如下代码,用 MyJsonValueProviderFactory 类代替 System.Web.Mvc.dll 程序集中的 JsonValueProviderFactory 类。

     
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    ValueProviderFactories.Factories.Remove(ValueProviderFactories.Factories.OfType<JsonValueProviderFactory>().FirstOrDefault());
    ValueProviderFactories.Factories.Add(new MyJsonValueProviderFactory());

     至此,.NET MVC 超出 maxJsonLength 的问题终于解决了!

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  • 原文地址:https://www.cnblogs.com/yanglang/p/8830837.html
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