NHibernate中Oracle字段类型Clob数据长度过大问题详解数据库

问题特别奇怪，按理说Clob字段不存在长度过大的问题，但在实际使用中却会提示这个问题。

而且字符特别少时，没有问题，特别长时也没有问题，长度在在1千到五千之前就会有问题。

实际上因为把Clob字段作为varchar所以会出现长度问题。修改如下：

添加类继承NHibernate中的IUserType

 public abstract class PatchForOracleLobField : IUserType 
    { 
        public PatchForOracleLobField() 
        { 
        } 
        public bool IsMutable 
        { 
            get { return true; } 
        } 
        public System.Type ReturnedType 
        { 
            get { return typeof(String); } 
        } 
        public SqlType[] SqlTypes 
        { 
            get 
            { 
                return new SqlType[] { NHibernateUtil.String.SqlType }; 
            } 
        } 
        public object DeepCopy(object value) 
        { 
            return value; 
        } 
        public new bool Equals(object x, object y) 
        { 
            return x == y; 
        } 
        public int GetHashCode(object x) 
        { 
            return x.GetHashCode(); 
        } 
        public object Assemble(object cached, object owner) 
        { 
            return DeepCopy(cached); 
        } 
        public object Disassemble(object value) 
        { 
            return DeepCopy(value); 
        } 
        public object NullSafeGet(IDataReader rs, string[] names, object owner) 
        { 
            return NHibernate.NHibernateUtil.StringClob.NullSafeGet(rs, names[0]); 
        } 
        public abstract void NullSafeSet(IDbCommand cmd, object value, int index); 
        public object Replace(object original, object target, object owner) 
        { 
            return original; 
        } 
 
    }

重写clob字段

 public class OracleClobField : PatchForOracleLobField 
    { 
        public override void NullSafeSet(IDbCommand cmd, object value, int index) 
        { 
            if (cmd is OracleCommand) 
            { 
                //CLob、NClob类型的字段，存入中文时参数的OracleDbType必须设置为OracleDbType.Clob 
                //否则会变成乱码（Oracle 10g client环境） 
                OracleParameter param = cmd.Parameters[index] as OracleParameter; 
                if (param != null) 
                { 
                    param.OracleType = OracleType.Clob;// 关键就这里啦 
                    param.IsNullable = true; 
                } 
            } 
            NHibernate.NHibernateUtil.StringClob.NullSafeSet(cmd, value, index); 
        } 
    }

实际使用

 [ActiveRecord("EAS.T_ProdGroupActivity")] 
    public class ProdGroupActivity:  EasActiveRecordCRUDEx<ProdGroupActivity> 
    {	 
		 
		#region property 
		 
		/// <summary> 
		/// Property PGA_ID 
		/// </summary> 
		[PrimaryKey(PrimaryKeyType.Sequence, "PGA_ID",SequenceName = "EAS.Seq_ProdGroupActivity")] 
		public int PGA_ID 
		{ 
            get; 
            set; 
        }        
		/// <summary> 
		/// Property PGA_Content 
		/// </summary> 
		[Property("PGA_Content", "DHC.EAS.Entity.OracleClobField,Eas.Entity")] 
		public string PGA_Content 
		{ 
            get; 
            set; 
        }		 
		#endregion 
	}

核心是修改特性[Property(“PGA_Content”, “DHC.EAS.Entity.OracleClobField,Eas.Entity”)]

第一个参数是映射的字段，第二个参数是新定义的clob字段完成的名称和所在程序集