使用 JSON JavaScriptSerializer 进行序列化或反序列化时出错。字符串的长度超过了为 maxJsonLength 属性设置的值
Posted donchen-c
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了使用 JSON JavaScriptSerializer 进行序列化或反序列化时出错。字符串的长度超过了为 maxJsonLength 属性设置的值相关的知识,希望对你有一定的参考价值。
<system.web.extensions> <scripting> <webServices> <jsonSerialization maxJsonLength="20971520"/> </webServices> </scripting> </system.web.extensions>
在自动提示下,很顺畅的加上了几行代码,以为这是个简洁的解决方案,但是运行网站之后报以下错误:
分析器错误消息: 无法识别的配置节 system.web.extensions。
这似乎又是碰到了一家人不认识的情况,既然无法识别为什么能带智能感知的方式输出,而且是已system.web开头的,按道理不会识别不出的。以为是拼写错误,经过进一步搜索之后,原来是缺乏了声明,加上对节点的声明即可(很大一串的内容)。
<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/> <sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="Everywhere"/> <section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/> <section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/> <section name="roleService" type="System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/> </sectionGroup> </sectionGroup> </sectionGroup>
加入了声明之后,运行正常,但是问题依旧还在,而且不管maxJsonLength设置成多大都无效,就算改成1个字符,居然还能跑起来。碰到这个问题只能进一步的搜索。在这篇文章中找到了原委http://weblogs.asp.net/rashid/archive/2009/03/23/submitting-my-first-bug-after-asp-net-mvc-1-0-rtm-release.aspx。
原来MVC框架内置的JsonResult代码中,在使用JavaScriptSerializer时,都是采用的默认值,没有从maxJsonLength读取值,即忽略了这个配置。要想使用配置中的值,只能自定义一个JsonResult,重写原JsonResult的ExecuteResult方法,于是定义一个ConfigurableJsonResult,代码如下:
public class ConfigurableJsonResult : JsonResult { public override void ExecuteResult(ControllerContext context) { if (context == null) { throw new ArgumentNullException("context"); } if (JsonRequestBehavior == JsonRequestBehavior.DenyGet && String.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase)) { throw new InvalidOperationException("This request has been blocked because sensitive information could be disclosed to third party web sites when this is used in a GET request. To allow GET requests, set JsonRequestBehavior to AllowGet."); } HttpResponseBase response = context.HttpContext.Response; if (!String.IsNullOrEmpty(ContentType)) { response.ContentType = ContentType; } else { response.ContentType = "application/json"; } if (ContentEncoding != null) { response.ContentEncoding = ContentEncoding; } if (Data != null) { JavaScriptSerializer serializer = new JavaScriptSerializer(); ScriptingJsonSerializationSection section = ConfigurationManager.GetSection("system.web.extensions/scripting/webServices/jsonSerialization") as ScriptingJsonSerializationSection; if (section != null) { serializer.MaxJsonLength = section.MaxJsonLength; serializer.RecursionLimit = section.RecursionLimit; } response.Write(serializer.Serialize(Data)); } } }
这样在返回长字符内容的json结果时,直接替换原JsonResult即可,同时也兼顾了可配置的灵活性。
以上是关于使用 JSON JavaScriptSerializer 进行序列化或反序列化时出错。字符串的长度超过了为 maxJsonLength 属性设置的值的主要内容,如果未能解决你的问题,请参考以下文章
Java中使用org.json和json-lib解析JSON