N-Hibernate中的长字符串与Oracle导致错误

Question

我使用oracle作为db和流利的Nhibernate进行映射。

下面是我的对象类

public class UserFieldEvent 
    { 
     public virtual int Id { get; set; } 
     public virtual UserFieldBase UserField { get; set; } 
     public virtual EventType EventType { get; set; } 
     public virtual string EventScript { get; set; } 
    } 

属性EventScript的长度可以是从0到4000。 在我提出的列类型EventScript一个CLOB数据库。

下面是我的映射类：

public UserFieldEventMap() 
     { 
      Table("TBLDS_USERFIELDEVENT"); 
      Id(x => x.Id).GeneratedBy.Sequence("SEQDS_USERFIELDEVENT"); 
      Map(x => x.EventType).CustomType<EventType>(); 
      Map(x => x.EventScript).CustomSqlType("CLOB"); 
      References(x => x.UserField).Column("USERFIELDBASEID"); 
     } 

现在，每当EventScript的长度大于2000我得到的错误“ORA-01461：只能用于插入到LONG列绑定一个LONG值”同时将对象保存到数据库中。任何人都可以提供帮助。

Answer 1

这是.NET提供的System.Data.OracleClient.OracleConnection驱动程序的已知问题。修复方法是使用Oracle提供的ODP.net客户端Oracle.DataAccess.Client.OracleConnection（请参阅：http://nuget.org/packages/odp.net.x86/）或使用以下解决方法（参考：http://thebasilet.blogspot.be/2009/07/nhibernate-oracle-clobs.html）。

public class CustomOracleDriver : OracleClientDriver 
{ 
    protected override void InitializeParameter(System.Data.IDbDataParameter dbParam, string name, SqlType sqlType) 
    { 
     base.InitializeParameter(dbParam, name, sqlType); 


     // System.Data.OracleClient.dll driver generates an ORA-01461 exception because 
     // the driver mistakenly infers the column type of the string being saved, and 
     // tries forcing the server to update a LONG value into a CLOB/NCLOB column type. 
     // The reason for the incorrect behavior is even more obscure and only happens 
     // when all the following conditions are met. 
     // 1.) IDbDataParameter.Value = (string whose length: 4000 > length > 2000) 
     // 2.) IDbDataParameter.DbType = DbType.String 
     // 3.) DB Column is of type NCLOB/CLOB 

     // The above is the default behavior for NHibernate.OracleClientDriver 
     // So we use the built-in StringClobSqlType to tell the driver to use the NClob Oracle type 
     // This will work for both NCLOB/CLOBs without issues. 
     // Mapping file must be updated to use StringClob as the property type 
     // See: http://thebasilet.blogspot.be/2009/07/nhibernate-oracle-clobs.html 
     if ((sqlType is StringClobSqlType)) 
     { 
      ((OracleParameter)dbParam).OracleType = OracleType.NClob; 
     } 
    } 
} 

你需要更新你的SessionFactory使用该驱动程序，以及更新任何CLOB映射使用StringClob自定义类型

Map(x => x.EventType).CustomSqlType("Clob").CustomType("StringClob");