Web Service调用Nhibernate数据访问异常：xx cannot be serialized because it does not have a parameterless constructor

最新推荐文章于 2024-04-04 14:37:19 发布

原创最新推荐文章于 2024-04-04 14:37:19 发布 · 839 阅读

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#constructor #service #web #namespaces #string #object

当使用NHibernate进行数据访问并在WebService中返回实体时，可能遇到由于代理类型缺少无参数构造函数而导致的序列化错误。解决方法之一是禁用实体类的延迟加载。

web servcie调用nHibernate的数据访问代码读取数据库并生成一个实体实例时，得到了如下异常信息：

An exception of type 'System.Web.Services.Protocols.SoapException' occurred in System.Web.Services.dll but was not handled in user code

Additional information: System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: CProxyTypeTheGuide_BusinessAddressBusiness_NHibernate_ProxyINHibernateProxy1 cannot be serialized because it does not have a parameterless constructor.
   at System.Xml.Serialization.TypeDesc.CheckSupported()
   at System.Xml.Serialization.TypeScope.GetTypeDesc(Type type, MemberInfo source, Boolean directReference, Boolean throwOnError)
   at System.Xml.Serialization.XmlSerializationWriter.CreateUnknownTypeException(Type type)
   at System.Xml.Serialization.XmlSerializationWriter.CreateUnknownTypeException(Object o)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write2_Address(String n, String ns, Address o, Boolean isNullable, Boolean needType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write4_Account(String n, String ns, Account o, Boolean isNullable, Boolean needType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write10_GetByIDResponse(Object[] p)
   at Microsoft.Xml.Serialization.GeneratedAssembly.ArrayOfObjectSerializer9.Serialize(Object objectToSerialize, XmlSerializationWriter writer)
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id)
   --- End of inner exception stack trace ---
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id)
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle)
   at System.Web.Services.Protocols.SoapServerProtocol.WriteReturns(Object[] returnValues, Stream outputStream)
   at System.Web.Services.Protocols.WebServiceHandler.WriteReturns(Object[] returnValues)
   at System.Web.Services.Protocols.WebServiceHandler.Invoke()
   --- End of inner exception stack trace ---

似乎nHibernate的内部实现没有很好的支持xml serialization. 这篇blog中提高了一个方法可以解决此问题：将有关的实体类的lazy load 关掉。是的，这要牺牲性能。
http://rebelheart.squarespace.com/blog/web-services-and-nhibernate.html (需要代理才能打开此链接)