如何使用NHibernate(Fluent)将DateTime属性映射到数据库中的2个varchar列？

Question

我正在处理一个遗留数据库,它在一些表中将日期和时间字段作为char(8)列(分别格式化为yyyyMMdd和HH:mm:ss).如何将2个char列映射到单个.NET DateTime属性？我尝试了以下内容,但我得到了"无法访问setter"错误,因为DateTime Date和TimeOfDay属性是只读的:

public class SweetPocoMannaFromHeaven
{    
    public virtual DateTime? FileCreationDateTime { get; set; }
}

.

mapping.Component<DateTime?>(x => x.FileCreationDateTime,
            dt =>
            {
                dt.Map(x => x.Value.Date,
                    "file_creation_date");
                dt.Map(x => x.Value.TimeOfDay,
                    "file_creation_time");
            });

我也尝试过为DateTime定义一个IUserType,但我无法理解.我已经做了大量的谷歌搜索,但我还是无法弄明白.处理这个愚蠢的遗留数据库约定的最佳选择是什么？一个代码示例会有所帮助,因为对于一些这些更加模糊的场景的文档并不多.

Answer 1

您需要ICompositeUserType来处理多个列.您需要加强错误检查,解析格式等,但这里是您的起点.

HTH,
Berryl

public class LegacyDateUserType : ICompositeUserType
{

    public new bool Equals(object x, object y)
    {
        if (x == null || y == null) return false;
        return ReferenceEquals(x, y) || x.Equals(y);
    }

    public int GetHashCode(object x) {
        return x == null ? typeof (DateTime).GetHashCode() + 473 : x.GetHashCode();
    }

    public object NullSafeGet(IDataReader dr, string[] names, ISessionImplementor session, object owner)
    {
        if (dr == null) return null;

        var datePortion = NHibernateUtil.String.NullSafeGet(dr, names[0], session, owner) as string;
        var timePortion = NHibernateUtil.String.NullSafeGet(dr, names[1], session, owner) as string;

        var date = DateTime.Parse(datePortion);
        var time = DateTime.Parse(timePortion);
        return date.AddTicks(time.Ticks);
    }

    ///<summary>
    /// Write an instance of the mapped class to a prepared statement. Implementors 
    /// should handle possibility of null values. A multi-column type should be written 
    /// to parameters starting from index.
    ///</summary>
    public void NullSafeSet(IDbCommand cmd, object value, int index, ISessionImplementor session) {
        if (value == null) {
            // whatever
        }
        else {
            var date = (DateTime) value;
            var datePortion = date.ToString("your date format");
            NHibernateUtil.String.NullSafeSet(cmd, datePortion, index, session);
            var timePortion = date.ToString("your time format");
            NHibernateUtil.String.NullSafeSet(cmd, timePortion, index + 1, session);
        }
    }

    public object GetPropertyValue(object component, int property)
    {
        var date = (DateTime)component;
        return property == 0 ? date.ToString("your date format") : date.ToString("your time format");
    }

    public void SetPropertyValue(object component, int property, object value)
    {
        throw new NotSupportedException("DateTime is an immutable object.");
    }

    public object DeepCopy(object value) { return value; }

    public object Disassemble(object value, ISessionImplementor session) { return value; }

    public object Assemble(object cached, ISessionImplementor session, object owner) { return cached; }

    public object Replace(object original, object target, ISessionImplementor session, object owner) { return original; }

    ///<summary>Get the "property names" that may be used in a query.</summary>
    public string[] PropertyNames { get { return new[] { "DATE_PORTION", "TIME_PORTION" }; } }

    ///<summary>Get the corresponding "property types"</summary>
    public IType[] PropertyTypes { get { return new IType[] { NHibernateUtil.String, NHibernateUtil.String }; } }

    ///<summary>The class returned by NullSafeGet().</summary>
    public Type ReturnedClass { get { return typeof(DateTime); } }

    ///<summary>Are objects of this type mutable?</summary>
    public bool IsMutable { get { return false; } }

}

===流畅的映射(假设自动化w/override类)====

 public void Override(AutoMapping<MyClass> m)
 {
     ....
     m.Map(x => x.MyDateTime).CustomType<LegacyDateUserType>();
 }